The Effects of Caffeine Alone, and in Combination with Nicotine, on Several Behaviors in Rats

Western Michigan University ScholarWorks at WMU

Master's Theses Graduate College

12-1983

Judith S. DeVoe

Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses

Part of the Experimental Analysis of Behavior Commons

Recommended Citation DeVoe, Judith S., "The Effects of Caffeine Alone, and in Combination with Nicotine, on Several Behaviors in Rats" (1983). Master's Theses. 1608. https://scholarworks.wmich.edu/masters_theses/1608

This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. THE EFFECTS OF CAFFEINE ALONE, AND IN COMBINATION WITH NICOTINE, ON SEVERAL BEHAVIORS IN RATS

Judith S. DeVoe

A Thesis Submitted to the Faculty of The Graduate College in partial fu lfillm en t of the requirements for the Degree of Master of Arts Department of Psychology

Western Michigan University Kalamazoo, Michigan December 1983

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THE EFFECTS OF CAFFEINE ALONE, AND IN COMBINATION WITH NICOTINE, ON SEVERAL BEHAVIORS IN RATS

Judith S. DeVoe

Western Michigan University

Several doses of caffeine-sodium benzoate (0.0, 2.5, 5.0, 10.0 & 20.0

mg/kg, stated as salt) were administered daily by intraperitoneal injec

tions (IP) for an in itia l twelve consecutive days which constituted

Phase I . A probe-dose of nicotine (2.0 mg/kg) was administered in com

bination with each caffeine dose for the following seven days comprising

Phase I I . Removal of nicotine subsequent to the last day of Phase I I

initiated a second caffeine-only (nicotine withdrawal) condition, Phase

I I I . Tests of locomotion and aggression ensued at various points of

the study and water intakes and body weights were recorded daily, prior

to injections. Overall, locomotion increased as a function of caffeine

dose with the exception on Day 1 of Phase I I . Muricidal aggression was

enhanced at higher doses of caffeine, but not with lower doses. Even

though previous research indicated nicotine's a b ility to suppress

the muricide, nicotine did not suppress the caffeine-induced attack

analyzed in the present study. Caffeine markedly increased water con

sumption across all phases as a function of dose, and the 10.0 mg/kg

dose was sta tistic a lly different from all other doses. The 2.0 mg/kg

nicotine dose in Phase I I produced additional increases in water intake,

in comparison to Phase I , regardless of the concurrently administered

dose of caffeine. Caffeine dose was also found to subtly influence

body weight.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

Several individuals deserve considerable recognition because of

th eir interest, support and encouragement. I would like to thank Dr.

Gault for his continued guidance regarding our conversations on the

reproachment between Clinical and Experimental Psychology. Special

appreciation to Robert Sewell as an educator, mentor, and friend for

the extensive hours he has generously poured into editing and for many

stimulating discussions, in addition to organizing the laboratory

necessary to the acquisition of the present experiment. To Dr. Murry

Cooper at the Upjohn Company for his time and fle x ib ility in the

statistical analysis of the data, including valuable comments and ideas

in reference to the experimental design. To Jeffry Gallus for assembling

the wheel-running equipment, drug preparation, and for his time and

ingenuity in the assistance of the preparation of Figures 1-6. To Kevin

Nanry for helping with the data collection throughout the experiment.

Finally, to all of those very special individuals and co-workers at

Borgess Medical Center who have been a strong source of motivation and

support.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS

This reproduction was made from a copy of a document sent to us for microfilming. While the most advanced technology has been used to photograph and reproduce this document, the quality of the reproduction is heavily dependent upon the quality of the material submitted.

The following explanation of techniques is provided to help clarify markings or notations which may appear on this reproduction.

1.The sign or “target” for pages apparently lacking from the document photographed is “Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure complete continuity.

2. When an image on the film is obliterated with a round black mark, it is an indication of either blurred copy because of movement during exposure, duplicate copy, or copyrighted materials that should not have been filmed. For blurred pages, a good image of the page can be found in the adjacent frame. If copyrighted materials were deleted, a target note will appear listing the pages in the adjacent frame.

3. When a map, drawing or chart, etc., is part of the material being photographed, a definite method of “sectioning” the material has been followed. It is customary to begin filming at the upper left hand comer of a large sheet and to continue from left to right in equal sections with small overlaps. If necessary, sectioning is continued again—beginning below the first row and continuing on until complete.

4. For illustrations that cannot be satisfactorily reproduced by xerographic means, photographic prints can be purchased at additional cost and inserted into your xerographic copy. These prints are available upon request from the Dissertations Customer Services Department.

5. Some pages in any document may have indistinct print. In all cases the best available copy has been filmed.

University Micnxilms International 300 N. Zeeb Road Ann Arbor, Ml 48106

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1322422

DEVOE, JUDITH SUE

THE EFFECTS OF CAFFEINE ALONE, AND IN COMBINATION WITH NICOTINE, ON SEVERAL BEHAVIORS IN RATS

WESTERN MICHIGAN UNIVERSITY M.A. 1983

University Microfilms International 300 N. Zeeb Road, Ann Arbor, Ml 48106

In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V .

1. Glossy photographs or pages ______

2. Colored illustrations, paper or print _____

3. Photographs with dark background _____

4. Illustrations are poor copy ______

5. Pages with black marks, not original copy ______

6. Print shows through as there is text on both sides of page ______

7. Indistinct, broken or small print on several pages ^

8. Print exceeds margin requirements ______

9. Tightly bound copy with print lost in spine______

10. Computer printout pages with indistinct print ______

11. Page(s) ______lacking when material received, and not available from school or author.

12. Page(s) ______seem to be missing in numbering only as text follows.

13. Two pages numbered ______. Text follows.

14. Curling and wrinkled pages ______

15. Other______

University Microfilms International

ACKNOWLEDGEMENTS ...... i i

LIST OF FIGURES ...... iv

Chapter

I . INTRODUCTION ...... 1

I I . METHOD ...... 7

Subjects ...... 7

Apparatus ...... 7

Procedure ...... 8

Drug Preparationand Administration ...... 9

Statistical Analysis ...... 10

I I I . RESULTS ...... 11

Effects on Water Intake ...... 11

Effects on Body Weight ...... 14

Effects on Locomotion ...... 14

Effects on Muricidal Aggression ...... 19

IV. DISCUSSION ...... 21

BIBLIOGRAPHY ...... 28

i i i

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Figure

1. The effect of caffeine dose alone, and in combination wicn 2.0 mg/kg nicotine, upon average number of m in ilite rs of water consumed (+ standard error) plotted as a function of day of treatment. Superimposed upon the saline-control (0.0 mo/kg) graph is drawn an horizontal line which represents that average number of m illilite rs of water consumed in Phase I , and is reproduced on each of the other doses: graphs for comparison purposes ...... 12

2. The effect of caffeine dose upon average m illilite rs of wacer consumed (N=6/group) across Phases I , II & I I I ...... 13

3. The effect of caffeine dose upon average body weight (+ standard errors) at each of four junctures in tns study: Phase I, Day 1; Phase I , Day 12; Phase I I , Day 7; ^hasa I I I , Day 5 ...... 15

4. The effects of caffeine dose given alone (Phase I, Day 12), in combination with 2.0 mg/kg nicotine (Phase I I , Days 1 and 6 ), and under withdrawal from nicotine (Phase I I I , Day 6 ), upon number of running-wheel revolutions. Bars indicate the average number of revolutions vi^o/group) in 30-minute tesc sessions (+ standard errors) ...... 15

5. Top graph: The influence of acuce 2.0 mg/kg (Phase I I , Day i' and sub-acute 2.0 mg/kg nicctine (Phase I I I , Day 6) plctcad as a function of caffeine dose-in-combi nation upon wheel--'unning a c tiv ity . Data are expressed as average number of revolutions change (^ standard errors! from wneel-running values collected under caffeine along (Baseline = Phase I, Day 12). Bottom graph: The influence of caffeine dose upon locomotion (Phase I I I , Day 6) six days after sub-acute history with 2.0 mg/kg treatments. Data are expressed as average numoer of revolu tions change _r standard errors) from wheel-running values collected on the 7th day of nicotine plus caffeine ...... 18

6. The effect of caffeine alone, and in combination with 2.0 mg/kg nicocine, upon numoer of muricidal responses (24-hour exposures to one mouse per rat, N=6/group) w*:thin each caffeine cose level. The four trials occurred respectively at Phase I , Day 12; Phase I I , Day 1; Phase I I , Day 7; and Phase I I I , Day 6. Each oar represents one mouse-kill ...... 20

: v

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I

INTRODUCTION

Caffeine, one of the most widely self-administered central nervous

system (CNS) stimulants in North America (Winsted, 1979), is found in

coffee, tea, soda pop, chocolate and numerous over-the-counter pre

parations. When the drug is consumed in large quantities, a psychiatric

disorder termed "caffeinism" can be induced (American Psychiatric As

sociation, 1980) causing symptoms such as "tension", "urge to cry",

insomnia, ir r it a b ilit y , restlessness, and tremor (e .g ., Neil, Hemmelhock,

Malinger, Malinger, & Hannie, 1978; Bezchibnyk & J effries, 1981; Greden,

1974; Greden, Fontaine, Lubetsky & Chamberlin, 1978) which have some

times confounded other psychiatric diagnoses. While caffeinism represents

a severe symptomology, most often associated with a long self-admini

stration history, some of caffeine's behavioral effects appear under

acute, lower doses (e .g ., Goldstein, Kaizer & Whitby, 1969). Increased

ir r it a b ility in humans (e .g ., DeFreitas & Schwartz, 1979), altered

water intake and a purported "tolerance lia b ility " in rats (e .g .,

Wayner & Kleinrock, 1978; Wayner Jolicoeur, Rondeau & Barone, 1976) are

among caffeine's noted behavioral actions.

Various laboratory, non-human assays have been employed to further

analyze those behavioral effects of caffeine originally observed in

human recipients. For instance, evidence of caffeine-induced i r r it a

b ility has been sought using certain models of aggression employing

laboratory animals. Caffeine has increased shock-induced attack in

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. both the rat (Eichelman, Orenberg, Hackley & Barchas, 1978) and squirrel

monkey (Emley & Hutchinson, 1983). Caffeine has not been found to

enhance muricidal aggression (Eichelman et a l., 1978), but has been

seen to reverse the anti-muricidal effects of chlordiazepoxide (Quenzer

& Feldman, 1974). In addition, stressed animals (chronically isolated

beginning immediately at weaning) treated with caffeine have evidenced

greater pathophysiology and higher mortality rates than do socialized

subjects (Henry & Stephens, 1980). Frequent fighting in the stressed

group possibly contributed to the higher percentage of deaths.

A second behavioral action of caffeine, altered water balance, has

been examined, albeit sparsely, also using laboratory animals (e .g .,

Markel, Wayner, Jolicoeur & Mintz, 1981). Acute caffeine treatment

yields diuresis, and chronic treatment can produce tolerance to di

uretic effects (e.g., Rail, 1980). High doses, but not low, of acute

caffeine have suppressed schedule-induced polydipsia in rats of reduced

body weights and chronic administration has produced tolerance to this

effect (Wayner et al, 1976). When rats returned to free-feeding weights,

low caffeine doses enhanced polydipsic drinking. In another study,

Merkel, Wayner, Jolicoeur & Mintz (1981) treated rats with several caf

feine doses and showed dose-related effects on home-cage food and water

intakes, dependent upon conditions. A high dose (100.0 mg/kg) attenuated

both food and water consumptions, for all conditions. A low dose (3.125

mg/kg) increased 1-hour water consumption in the 23-hour water deprived

condition, as did the 12.5 mg/kg dose in the free-feeding and drinking

condition.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Caffeine, a psychomotor stimulant, increases locomotion in animals

(e .g ., Estler, 1973; Thethapandha, Maling, and G ilette, 1972). Mon

golian gerbils significantly increase wheel running activity when

treated with low to moderate caffeine doses, however, gerbils treated

with high doses of caffeine display decreased wheel running as compared

to those treated with saline (Pettijohn, 1979). Caffeine markedly in

creases locomotion, and simultaneously decreases social interactions in

rats (F ile and Hyde, 1979). When illumination and environmental fami

lia r ity are manipulated during tests of locomotion and social interaction,

anxiety indices have been inferred (e.g., File and Hyde, 1979). Assays

have revealed that test illumination can modify the locomotor effects

of certain CNS stimulants (e .g ., d-amphetamine and methylphenidate) but

not those of caffeine (Kallman & Issac, 1975).

In summary, caffeine is a widely self-administered, socially ap

proved substance associated with numerous untoward behavioral side-effects.

These influences have been observed in human caffeine recipients, consist

notably of ir r it a b ilit y , altered water balance and hyperactivity, and

have been analyzed to certain degrees in various animal preparations.

Few investigations have analyzed these three side-effects in the same

subjects. Therefore, the major purpose of the present study was to

examine effects of several caffeine doses on muricide, water intake,

wheel running and body weight in the same rodent subjects. It was hoped

that a unique constellation of effects would emerge indicating relative

selectivity of caffeine's actions. To the extent that a unique, readily

reproduced constellation of effects could be demonstrated, i t was believed

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. that future investigations of adverse drug-drug interactions involving

caffeine might be expedited.

A drug's effects on behavior, when examined independently of another

compound, are not necessarily the same as when studied in drug-drug

combinations (e .g ., Hansten, 1971; G riffin and D'Arcy, 1979; Lasagna,

1978; Melmon & Gilman, 1980). Drug-drug interactions may change the

absorption, metabolism, distribution and/or elimination of a substance

( i . e ., it 's phamacokinetics) (e .g ., H o llister, 1978; Melmon & Gilman,

1980). For example, one chemical may effect the amount or rate of ab

sorption of another drug so that effective serum levels are never

reached, or, so that the rate of an effect's onset many be speeded

or delayed. Other examples of pharmacokinetic actions would include

when certain drugs increase or decrease drug metabolism and therefore

speed or slow elimination of other chemical agents. In addition to

pharmacokinetic interactions, drugs may act directly to fa c ilita te or

suppress the effects of other chemical agents and therefore produce

pharmacodynamic interactions (e .g ., H ollister, 1978; Melmon & Gilman,

1980). Accordingly, two substances may compete for, or a lte r, common

receptor sites (e.g., Melmon & Gilman, 1980.)

Given the above, it is plausible that caffeine's behavioral in

fluences can be substantially altered by drug-drug interactions

(either of the pharmacokinetic and/or pharmacodynamic sorts), and

various evidence has accrued which supports this notion. For instance,

in humans certain oral doses of caffeine in combination with pento

barbitone actually produce effects similar to placebo, suggesting that

the individual effects of the two drugs when given alone were cancelled

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 5

by the two agents being given in combination (Forrest, B eliville <1 3rown,

1972). In infrahuman subjects various caffeine doses as well as higher

doses of phenobarbitone or pentobarbitone eacn individually increase

locomotor a ctiv ity , yet when caffeine-barbituate combinations are given,

given, activity effects have appeared additive (Waldeck, 1975). In

mice, combined doses of ethanol and caffeine act to increase m otility

above those levels achieved under either drug administered alone (Waldeck,

1973). Further, caffeine with or without ethanol has facilitated the

reversal of motor activity induced by ET495 + Clonidine (Waldeck, 1973).

Since caffeine and nicotine often are concurrently sel--administered,

the possibility exists that nicotine frequently modifies caffeine's be

havioral influence. However, surprisingly little aata has been collected

regarding this p la u sib ility. That nicotine exerts powerful behavioral

actions is well-known and has been analyzed in numerous laboratory

animal investigations. For instance, nicotine has been shown co selec

tively suppress various measures of aggression (e .g ., Driscoll A Baettig,

1981; W aldbillig, 1980; Emley & Hutchinson, 1983), alter wacer balance

mechanisms (e .g ., Gritz and Jarvik, 1978; Sanger, 1978), influence oody

weight (e .g ., Sanger, 1978; McNair, and Bryson, 1983), and to markedly

change various indices of motor activity (e .g ., Stolerman, Fink, and

Jarvik, 1974; Clarke and Kumar, 1983; Bryson, 3iner, McNair. Serganay,

and Abrams, 1981). Given that caffeine and nicotine are frequently

self-administered in combination and that nicotine itself is behavioral^'

active, a second objective of the present study was to examine how

repeated nicotine administrations might modify reactions of rats already

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. receiving sub-acute caffeine treatments. A standard nicotine challenge

(2.0 mg/kg) was selected for simultaneous administration to rats also

already receiving any of five caffeine doses (0.0, 2.5, 5.0, 10.0, and

20.0 mg/kg). F inally, a third objective of the present study was to

tentatively assess how an extended caffeine history might alter reaction

to withdrawal from repeated nicotine treatments.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I I

Method

Subjects

Thirty female Sprague-Dawley rats, weight X" = 181 S.E. 7.9 gm

served as subjects. Animals were bred and raised in this laboratory,

and kept under conditions of constant temperature (23 C, ca) and lighting.

Subjects were randomly selected and assigned to one of five groups, com

prised of six rats each. For the duration of the experiment animals were

individually housed and provided water and rat chow (Rat Chow 5012,

Ralston-Purina Co., St. Louis, Mo.), ad libitum.

Apparatus

Water intake was monitored via 100 ml fluid reservoirs including

No. 6 stoppers and attached drink spouts (Corning 100 ml polystyrene

graduated cylinders, Corning Glass Works, Corning, N .Y.). The reservoirs

were fille d daily with tap water, inverted and attached by a wire spring

to individual stainless steel cages (32 cm x 24 x 20 cm; Unifab Corp.,

Kalamazoo, Michigan).

Separate body weights, in grams, were recorded daily from a top-

loading scale (Pelouze, Model 1000).

Motor activity was measured for individual performances on one of

three standard Wahmann Running Wheels (Wahmann Co., Baltimore, MD). Each

wheel (35 cm dia. x 11 cm wide) was contained in a separate, sound-

attenuating chamber (61 cm x 61 cm x 61 cm) equipped with masking white

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. noise (80 db), forced air ventilation, and illumination (7.5 volt, G.E.).

A microswitch and digital monitor served to measure revolutions in both

di rections.

Thirty female CF-1 mice, bred and raised in this laboratory, served

as targets for aggressive responses. One mouse was placed in each rat's

sage for a 24-hour period. Mouse mortality rate was recorded.

Procedure

Phase I: Once animals were assigned to respective groups to control

for homogeneity of weight-between-groups, an eight day acclimation period

followed in which daily water intake was recorded. Subsequently, control

animals were administered daily intraperitoneal injections of physio

logical saline solution and four experimental groups were administered

daily intraperitoneal injections of caffeine at one of four dose levels

(2.5, 5.0, 10.0 & 20.0 mg/kg). Each group continued to receive that dose

in itia lly assigned. Prior to each of 12 daily injections, water intake

and total body weights were measured and recorded for all groups (N = 6).

On the twelfth day of drug, one-half hour after injection, each animal

was placed in a running wheel for a thirty-minute test session. Once all

animals were returned to home cages a single female CF-1 mouse was

placed in each cage over a 24-hour period. Incurred death rates were

recorded and used as indices of rat aggression (muricide).

Phase I I : On the thirteenth day of study all animals received

previously assigned doses of caffeine, followed by a standard (2.0 mg/kg)

’ntraperitoneal (IP) injection of nicotine. One-half hour after injections,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. animals were placed in one of three running wheels and number of

revolutions were then recorded over single thirty-minute intervals.

Subsequently one CF-1 mouse was placed in each animal's home cage for

24 hours in a test of muricide. Both total body weights and 24-hour

water intake were recorded daily for seven days. Collection of locomo

tion and muricide data was again made, on the seventh day of Phase I I .

Phase I I I : For the remaining six days of study there occurred

a second caffeine-only condition; also termed the "nicotine with

drawal phase." Animals were administered th eir previous caffeine

doses as in Phases I and I I and both water intakes and body weights

were recorded for the fir s t five of these days. On the sixth day tests

of locomotion and muricide were again obtained.

Drug Preparation and Administration

Caffeine-sodium benzoate (50% caffeine, 50% benzoic acid, sodium

s a lt), Sigma Chemical Company, St. Louis, Missouri) was dissolved in

physiological saline to concentrations of 2.5, 5.0, 10.0 and 20.0

mg/ml. All statements of caffeine concentration and dosage (2.5, 5.0,

10.0 and 20.0 mg/kg) are given in terms of the sodium benzoate salt.

When nicotine treatments were given, these consisted of nicotine tartrate

(ICN Pharmaceuticals, In c ., Life Sciences Group, Plainview, New York)

dissolved into aqueous saline solution at a concentration of 2.0 mg/ml.

All injections were administered via the intraperitoneal route (IP) at

volumes of 1.0 ml/kg. All injections were administered subsequent to

24-hour water intake and body weight measures and 30 minutes prior to

tests of locomotion.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10

S tatistical Analysis

Effects of caffeine on water intake, body weight, and locomotion

were analyzed by multivariate analysis. A general linear models pro

cedure was utilized to contrast test days. Determinations for linear

or quadatic effects indicate the shape of the function. Effects of

caffeine on muricidal aggression were analyzed by a Generalized

Cochran-Mantel-Haenszel test s ta tis tic for Average Partial Associa

tion in Three-way contingency tables (Landis, Heymon & Koch, 1978;

Landis, Cooper, Kennedy & Koch, 1977).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I I I

Results

Effects on Water Intake

In the overall assessment of water intake there was observed

main effects of caffeine dose (p < 0.01). For this measure, neither

the linear dose-response evaluation nor the quadratic dose-response

evaluation reached statistical significance for either the intercept

or slope. Figure 1 presents the average water intake (m illilite rs )

for each caffeine dose group, across the three phases. The dashed

vertical lines serve to separate phases and the dashed horizontal lines

represent average water consumption for saline controls during Phase I

only and is reproduced upon each other dose group's data for comparison

purposes. As can be seen in Phase I , water intake was increased for

both the 5.0 mg/kg and 10.0 mg/kg dose groups compared to saline per

formance, and was significant for the 10.0 mg/kg group (p < 0.04). In

addition the 2.0 mg/kg nicotine treatments appeared to clearly enhance

water intake irrespective of the caffeine dose employed. The overall

assessment revealed a main effect of phase (p < 0.01), and this was re

lated to the intake enhancement under nicotine (Phase II). Overall

assessment revealed no interaction between caffeine dose and phase of

treatment (p < 0.31). Figure 2 displays the average water intake per

phase (m illiliters) for each group. In this figure, the intake-en

hancing influence of nicotine is emphasized.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12

Figure 1. The effect of caffeine dose alone, and in combination with 2.0 mg/kg nicotine, upon average number of m illi lite rs of water consumed (+_ standard error) plotted as a function of day of treatment. Superimposed upon the saline-control (0.0 mg/kg) graph is drawn a horizontal line which represents that average number of m illilite r s of water consumed in Phase I , and is reproduced on each of the other doses' graphs for comparison purposes.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ol to o *n z > -n m z o S m

11 o o z r> H m z o 2 3 m — > w s 2 55" r n ■ £ . + O l o to to tO Hi cm ro o o o O l o Ol (O to to o AVERAGE AVERAGE WATER INTAKE (ml) Ui o

- 0 0 GO- DAYS OF TREATMENT Reproduced with permission ofthe copyright owner. Further reproduction prohibited without permission. Figure 2. The effect of caffeine dose upon average m illiliters of water consumed (N=6/group) across Phases I , II and I I I .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. T| o z > TJ m z m o Ol

H z m o o □ nn 5 s m 5 s > ro> ■n a -n □ J □ S WS S o n n 'n ^ o o J I _ l 04 O -J- ro o _L AVERAGE WATER o _±_ INTAKE PER PHASE (ml)

ro o o o o 01 o ro bi o o DOSE OF CAFFEINE(mg/kg) Reproduced with permission ofthe copyright owner. Further reproduction prohibited without permission. 14

Effects on Body Weight

In the overall assessment of body weight data there emerged a main

effect of dose (p < 0.01). Multivariate analysis revealed statistical

significance for caffeine dose on body weight for both the intercept

(p < 0.02) and slope (p < 0.03) of the linear dose-response assessment,

and for the intercept (p < 0.01) , but not the slope (p < 0.47) of the

quadratic dose-response evaluation. Figure 3 displays total body

weights (grains) for all caffeine doses at various points in the study.

From le ft to right and top to bottom, the data appear as follows:

first day caffeine-only (Phase I); first day caffeine-plus-nicotine

(Phase I I ) ; seventh day caffeine-plus-nicotine (Phase I I ) ; and sixth day

of nicotine withdrawal (Phase I I I ) . A small expected weight increase was

noted as the study progressed (growth was seen from Day 1, Phase I to

Day 1, Phase I I ) . There was, however, no main effect of phase upon

weight nor was there a dose-byphase interaction.

Effects on Locomotion

The effects of sub-acute caffeine, alone and in combination with

nicotine, upon locomotion are displayed in Figure 4. Four running

wheel assessments were performed, one on each of the following oc

casions: Phase I, Day 12 (caffeine-only); Phase I I , Days 1 & 7

(caffeine-plus-nicotine); and Phase III, Day 6 (nicotine withdrawal).

As can be seen in Figure 4, caffeine produced a general increase in

locomotion, at the higher dose levels, in Phase I . Following this,

the addition of nicotine (2.0 mg/kg) to the treatment regimen yielded

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15

Figure 3. The effect of caffeine dose upon average body weight (_+ standard errors) at each of four junctures in the study: Phase I , Day 1; Phase I I , Day 1; Phase I I , Day 7; Phase III, Day 5.

BODY WEIGHT (GRAMS) 2 2 5 - 5 2 2 - 5 2 2 200 - 0 5 2 250-1 200 175- 175 0

- -

0.0 s DAY 1st 2.5 CAFFEINE NICOTINE DAY th 7 5.0 OY EGTAD CAFFEINE AND WEIGHT BODY 10.0

DOSE OF CAFFEINE CAFFEINE OF DOSE 20.0 mg/kg) (m OT NICOTINE POST 0.0 i NICOTINE s DAY 1st t DAY 6th 5 10.0 20.0 5.0 25 oc

Figure 4. The effect of caffeine dose given alone (Phase I, Day 12), in combination with 2.0 mg/kg nicotine (Phase I I , Days 1 and 7 ), and under withdrawal from nicotine (Phase I I I , Day 6) upon number of running-wheel revolutions. Bars indicate the average number of revolutions (N=6/group) in 30-minute test sessions {+_ 1.0 standard errors).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. REVOLUTIONS 0 5 3 0 0 4 0 5 4 0 0 3 2 5 0 0 5 2 200 1 5 0 - - 0 5 1 100- - 0 5 0 -

I □ 0.0 A 1 CAFFEINE 12 DAY DAY I CAFFEINE CAFFEINE I DAY NICOTINE & WHEEL RUNNING CAFFEINE AND NICOTINE AND CAFFEINE RUNNING WHEEL I OEO AFIE( kg) g /k g (m CAFFEINE OF DOSE .5 2 I I .0 5 A 6 POST-NICOTINE 6 DAY j j DAY 7 CAFFEINE CAFFEINE 7 DAY & NICOTINE 10.0 * I 20.0 I T

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17

marked locomotor suppression for all groups on Day 1 of Phase I I (hori

zontally striped bar); an effect which was significant (p < 0.01). By

contrast, on the 7th day of Phase I I all groups showed increased activity

(solid bar) in comparison to both the fir s t day of combined treatment

(p < 0.01) and to the assessment taken on the twelfth day of Phase I

(caffeine-alone) (p < 0.01) but was not significantly different than lo

comotion which occurred at the end of Phase I I I (p < 0.063). Overall

analysis of locomotor data using a linear models procedure revealed

significant main effects for both caffeine dose (p < 0.01) and phase of

treatment (p < 0.01), but not for an interaction of caffeine dose and

phase (p < 0.06). A comparison of test days, across all phases, showed

a significant linear dose effect (p < 0.01).

Locomotion data, collected during various phases of nicotine ex

posure (acute, sub-acute, and post-withdrawal), were further analyzed .

by plotting number of revolutions change from baseline values. The

results of this analysis are presented in Figure 5. In the top graph,

data collected under exposure to acute 2.0 mg/kg nicotine (Phase I I ,

Oay 1) and sub-acute 2.0 mg/kg nicotine (Phase I I , Day 7) are plotted

as a function of caffeine dose-in-combi nation upon wheel-running a ctiv ity .

Data are expressed as average number of revolutions change (+ standard

errors) from wheel-running values collected under caffeine alone (Base

line = Phase I , Day 12). The data collected under acute nicotine

exposure displays a dramatic locomotor suppression, as contrasted with

behavior under Day 12 caffeine-alone. Then, after seven daily admini

strations of 2.0 mg/kg nicotine, retesting of locomotion revealed a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13

Figure 5. Top graph: The influence of acute 2.0 mg/kg nicotine fPhase^ I I , Day 1) and sub-acute 2.0 mg/kg nicotine (Phase I I , Oay 7) plotted as a function of caffeine dose-in-combi nation upon wheel-running activity. Data are expressed as average number of revolutions change (+ standard error) from wheel running values collected under caffeine alone (Baseline = Phase I, Day 12). Bottom graph: the influence of caff aine aose upon locomotion (Phase I I I , Day 6) six days after sub-acute history with 2.0 mg/kg nicot’ ne treatments. Data are expressed as average number of revolutions change (+ standard errors) from wheel running values collected on the Tth day of mcotine- plus-caffeine.

NUMBER OF REVOLUTIONS CHANGE FROM BASELINE - -160 - -160 80-DY I DAY - 0 -8 160-1 40- 0 -4 120 120 160-1 - 0 4 - 0 8 120 - 0 4 - 0 8 o- o- - - - 0.0 O E F CAFFEINE OF DOSE 2.5 (mg/kg) 5.0 OTNCTN DY 6 DAY POST-NICOTINE CFEN ALONE) (CAFFEINE 10.0 20.0 A 7 DAY NICOTINE 2. mg/kg) m .0 (2 + CAFFEINE NICOTINE + CAFFEINE g/kg) m .0 (2 19

substantial elevation of motor activity, vis a vis data from both Day 12

caffeine-alone and Day 1 caffeine-plus-nicotine. This effect was con

sidered a preliminary indication of behavioral tolerence. In the lower

graph of Figure 5, data collected six days after the termination of sub

acute nicotine are presented. The data are expressed as average number

of revolutions change (+_ standard errors) from wheel-running values

collected on the 7th day of caffeine-plus-nicotine. As can be seen,

locomotor behavior declined between Phase I I and Phase I I I , yet this

decline was clearly dependent upon caffeine dose.

Effects on Muricidal Aggression

Figure 6 on muricide shows four trials (Tl, last day of Phase I;

T2, fir s t day Phase I I ; T3, last day Phase I I and T4, last day Phase

I I I ) of mouse mortality rate for each subject across all groups as a

function of caffeine dose (0.0, 2.5, 5.0, 10.0 & 20.0 mg/kg). In group

one there occurred one death on T3. In group four (10.0 mg/kg) three

subjects killed on all four trials. In the 20.0 mg/kg group, subject

two killed on T2, T3 and T4. These results suggest that muricidal ag

gression as a function of caffeine dose is suppressed at lower doses

and enhanced at higher doses. Apparently the standard 2.0 mg/kg dose

of nicotine failed to suppress aggressive responding with higher doses

of caffeine. Statistical analysis using the Generalized Cochran-

Mantel-Haensel test for average partial association in three-way

contingency tables revealed a significant muricide by tr ia l effect on

T3 verses Tl (p < 0.057) and no effect on T2 verses Tl or T4 verses T l.

Muricide as a function of dose shows a quadratic effect (p < 0.03.)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20

Figure 6. The effect of caffeine alone, and in combination with 2.0 mg/kg nicotine, upon number of muricidal responses (24- hour exposures to one mouse per rate, N = 6/group) within each caffeine dose level. The four tria ls occurred respectively at Phase I , Day 12; Phase I I , Day 1; Phase I I , Day 7; and Phase I I I , Day 6. Each bar represents one mouse-kill.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i MURICIDE AND CAFFEINE

SUBJECTS SUBJECTS SUBJECTS SUBJECTS SUBJECTS I 2 3 4 5 6 I 2 3 4 5 6 12 3 4 5 6 12 3 4 5 6 I 2 3 4 5 6

20.0

DOSE OF CAFFEINE (m g/kg) Reproduced Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV

DISCUSSION

Moderate doses of caffeine, given alone (Phase I) produced in

creased water intake and the 10.0 mg/kg dose induced elevated water

intake significantly higher than that under saline (see Figures 1 and

2 ). For comparison purposes, studies of caffeine's effects on water

intake are generally sparse (e.g., see Merkel, Wayner, Jolcoeur, and

Mintz, 1981). However, the present study's results stand at variance

with Cooper (1982) who reported that water-deprived rats evidenced

attenuated water drinking in 2-hour test sessions, and thus suggests

that caffeine-induced changes in water balance depends upon depri-

vational state and certain other experimental conditions. Wayner

et a l . , (1986) examined the effects of acute caffeine (3.125, 6.25,

12.5, 25.0, 50.0 and 100.0 mg/kg) on schedule-induced polydipsia

(SIP) in 1-hour test sessions and on related home-cage intakes with

rats at both 80% and 100% body weight. When at 80% weights, rats

consumed significantly more water in home cages under 50 and 100 mg/

kg treatments but drank less at 100 mg/kg in SIP test sessions. When

at 100% weights, rats consumed more home-cage water at 50 and 100 mg/

kg dose levels and displayed enhanced SIP under 3.125 mg/kg tre a t

ment but suppressed SIP under the 100 mg/kg dose level. A search for

tolerance to caffeine's SIP effects under 100 mg/kg doses given 8

times, one every other day, did demonstrate tolerance by the 5th tre a t

ment. Merkel et a l., (1981) further analyzed water intake effects of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. acute caffeine (3.125, 6.25, 12.5, 25.0, 50.0 and 100.0 mg/kg) with

rats maintained under various food or water deprivational conditions.

This later study clearly demonstrated that caffeine's influence on water

balance depends upon previous deprivational state. The present study

corroborates those findings of Wayner et al. (1976), Merkel et al.,

(1976) and Cooper (1982) which have all shown caffeine as active in

altering rodent water balance. The present study, however, appears to

be the firs t to examine the water intake-effects of repeated, daily

sub-acute caffeine treatments (0.0, 2.5, 5.0, 10.0 and 20.0 mg/kg).

In this regimen, no evidence of tolerance emerged throughout the Phase

I (12 days of caffeine alone) period.

In Phase I I standard probe doses of nicotine (2.0 mg/kg) were

given daily for seven days, to all subjects. Evaluation of the in

fluence of this nicotine dose alone was made by scrutinizing those

water intakes of the 0.0 mg/kg caffeine subjects during Phase II.

Here i t was seen that nicotine considerably enhanced drinking. When

2.0 mg/kg nicotine treatments were combined with the various caffeine

doses (2.5, 5.0, 10.0 and 20.0 mg/kg), intake enhancements were again

seen (see Figures 1 and 2, Phase I I ) . Statistical analysis revealed

that while there were main effects of Phase and of caffeine dose,

there occurred no Phase X caffeine-dose interaction. Few studies have

explored the potential dipsogenic influences of nicotine, in isolation,

le t alone in combintion with other chemical agents. One previous

study placed nicotine into rats' home-cage drinking water to examine

whether nicotine self-administration could be induced (Falkenborn et

a l., 1981). In that experiment water intake was suppressed under

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23

nicotine treatment yet i t remains unclear whether confounding variaoles

such as nicotine's taste and relative reinforcing properties were

actually what accounted for the observed effects. In another study,

Domino and Lutz (1973) injected nicotine intraperitoneally and effect

on SIP were then analyzed. Here too, nicotine was found to suppress

water intake. Our findings with nicotine at 2.0 mg/kg, given alone,

indicate that nicotine can function as a dipsogen, and thus runs con

trary to those data collected by both Falkenborn et a l., (1981) and

Domino and Lutz (1973). The potential determinants of the described

across-reports variance remain obscure.

Phase III constituted a return to the caffeine-only condition and

as such may be construed as the "nicotine-withdrawal" phase. In general,

institution of Phase I I I re-established lowered water intake levels;

comparable to those found in Phase I . This clearly discernable fa ll in

water consumption occurred regardless of the concommitant dose of caf

feine being administered. This within-groups reversal of water intake

effects, as seen across phases, adds to the evidence with which ic can

be asserted that nicotine can function as a dipsogen, even chough the

0.0 mg/kg nicotine control condition was not employed.

In summary, the present experiment appears to have been the fir s t

to examine caffeine's dipsogenic effect in combination with nicotine's

influence upon water balance. The present work reveals no preliminary

evidence of caffeine-nicotine interaction in the determination of water

intake. However, a much expanded nicotine dose range is necessary for

definitive remarks on this issue.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24

Caffeine dose was found to exert a relatively subtle influence on

body weight with slight elevations occurring at certain doses, yet when

various caffeine doses were each compared to saline, the results were

neither robust nor significant. This finding is in keeping with those

results of Henry and Stephens (1980) who chronically exposed mice to

caffeine via home-cage water supplies. Statistical analysis in the pre

sent study revealed no main effect of phase, and thus, a body weight

effect of nicotine was ruled out. Our lack of nicotine effect on body

weight is at variance with those results reported both by Baettig, Martin,

and Classen (1980) and by Falkeborn, Larsson and Nordberg (1981). In

both of these later two experiments nicotine was found to clearly sup

press rat body weights relative to vehicle-control subjects. It may

be that differences in route of administration account for differences

in nicotine's body weight effects across research reports. In both the

Baettig et a l. (1980) and the Falkeborn et a l. (1981) studies nicotine

was administered o rally, in home cage drinking water, and i t may be

that gustatory variables altered nicotine's influence that were not

operative in the present study which employed intraperitoneal injection.

McNair and Bryson (1983) have reported inhibition of weight-gain in 3

month old rats subcutaneously treated with nicotine for male subjects but

not for female animals. As such those findings of McNair and Bryson

(1983) are in agreement with those results here reported.

In the caffeine-only condition (Phase I) locomotion significantly

increased as a function of dose. These results are consistent with

the findings by Pettijohn (1979) using identical doses of caffeine as

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25

in this experiment. The highest dose produced no significant increases

in activity from controls. Chronically caffeine-treated rats (11 weeks)

demonstrated tolerance to the stimulant effects on locomotor activity

(Holtzman, 1983). The sub-acute caffeine treatments in Phase I did not

appear to produce "tolerance" to the stimulant effects of locomotor

activ ity .

Upon the fir s t administration of a standard "probe" dose of

nicotine (Day 1, Phase I I ) there occurred a marked depression of wheel

running across all groups relative to activity recorded in Phase I .

This depression has previously been noted in experimentally naive rats

receiving nicotine alone (Stolerman, Fink & Jarvik, 1973). The depressant

action of nicotine on locomotor activity in non-tolerant rats is blocked

by mecamyllamine, both a peripheral and central (CNS) blocker (Clarke &

Krumar, 1983). On the other hand, hexamethoniurn, a peripheral (CNS)

blocker had no effect on locomotor activity suggesting central actions

of nicotine.

By contrast, following seven consecutive days of caffeine-plus-

nicotine treatment, performance emerged well above that observed on the

two previous test sessions, thus suggesting the possible development of

"tolerance". To assert that tolerance occurred, an additional group

receiving nicotine on only the first and last days of Phase II would be

required. Nonetheless, tolerance to the depressive effects of nicotine

on behavioral measures is well documented (Hubbard & Gohd, 1974 &

Dougherty et a l. , 1981). Stolerman et a l . (1973) have demonstrated

that animals receiving three daily doses of nicotine for eight consecutive

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26

days remain tolerant up to 90 days after drug withdrawal. On Day 6

of nicotine withdrawal (Phase I I I ) a ctiv ity levels remained elevated

showing a slight but not significant decrease from Day 7 of combined

drug treatments, with the execption of the 20.0 mg/kg dose group. The

apparent "tolerance" to the depressant effects of nicotine on activity

has been shown to continue in the absence of repeated injections (Morrison

& Stephenson, 1972).

Both graphic and statistical analysis revealed that caffeine dose

had a major impact on the tendency of rats to k ill mice within 24-hour

aggression test sessions. This general finding, that caffeine increases

animal ir r it a b ilit y , has also been demonstrated in numerous other studies

(eg. Emley and Hutchinson, 1983; Eichelman, et a l., 1978). In addition,

Quenzer and Feldman (1975) have reported that caffeine can reverse the

anti-muricidal effects of chlordiazepoxide. In the present study, nico

tine neither induced muricidal responses nor did i t suppress muricide

which had been induced under the higher doses of caffeine. This later

result is somewhat surprising in that various other reports have docu

mented nicotine's aggression suppressive effects, employing various species

and attack induction and recording procedures (eg. Waldbillig, 1979;

Serntson, Beattie, and Walker, 1976; Emley and Hutchinson, 1983; Driscoll

and Baettig, 1981). The variables which account for a lack of nicotine's

aD ility to suppress caffeine-induced muricide remain unknown. The pre

sent report does suggest however, that nicotine may not interact with

caffeine to alter aggressive responses within the muricidal paradigm.

Complete address of this issue w ill, however, require an extended nico

tine dose range.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27

In summary, the most striking effects occurred with the 10.0 mg/kg

dose of caffeine. Water intake was significantly enhanced across phases

at 10 mg/K, in comparison to the other doses (see Figures 1 and 2 ). Also,

consistent mouse-killing was observed on all four repeated tria ls of

aggression, and, nicotine was not shown to suppress this behavior (see

Figure 6). Overall, locomotion significantly increased as a function

of caffeine dose in Phase I and by comparison was significantly depressed

on Day 1 of Phase I I (see Figures 4 and 5). This in itia l depression on

activity induced by nicotine in non-tolerant animals is well documented

(Clarke & Kumer, 1983; Stolerman et a l. 1973: Stolerman et a l , 1974).

However, by Day 7 of Phase I I , apparent tolerance to the depressant

effects of nicotine had developed, and activity levels even exceeded

those observed on the fir s t caffeine-only condition for all groups. Al

though no drug-drug interaction effects were s ta tis tic a lly detected, i t

has seemed reasonable to expect interaction effects given certain

"opposing" effects of nicotine and of caffeine on aggression and water

intake as described in the literatu re. The present study lacked an

appropriate caffeine-only control group across all phases of treatment

with which to fully assess interaction possibilities. Additionally,

several doses of nicotine in combination with several doses of caffeine

would provide a more useful assessment of interaction possibilities.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. BIBLIOGRAPHY

American Pharmaceutical Association. Evaluation of Drug Interactions (second ed .). Washington, D.C.: 1976.

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (third ed .). Washington, D.C.: 1980.

Baettig, K. Martin, J. R ., & Classen, W. Nicotine and amphetamine: Differential tolerance and no cross-tolerance for ingestive effects. Pharmacology Biochemistry & Behavior, 1980, 12_, 107-111.

Barone, F. C., Wayner, M. J . , & Kleinnoch, S. Effects of caffeine on FT- 1 min schedule induced drinking at different body weights. Pharmacology Biochemistry and Behavior, 1979, 11_, 347-350.

Bernteon, G. G., Beattie, M.S., & Walker, J.M. Effects of nicotonic and muscarinic compounds on biting attack in the cat. Pharmacology Biochemistry and Behavior, 1976, 5_, 235-239.

Bezchlibnyk, K. Z., & Jeffries, J. J. Should psychiatric patients drink coffee? Canadian Medical Association Journal, 1981, 124, 357-358.

Bryson, R., Biner, P. M., McNair, E., Bergundy, M., & Abrams, O.R. Effects of nicotine on two types of motor activity in rats. Psychopharmocology, 1981, 7^, 168-170.

Clarke, P.B.S., & Kuman, R. The effects of nicotine on locomotor activity in non-tolerant and tolerant rats. British Journal of Pharmacology, 1983, 78_, 329-337.

Cooper, S. J. Caffeine-induced hypodypsia in water deprived rats: Relationship with benzodiazapine mechanisms. Pharmacology Biochemistry and Behavior, 1982, 17_, 481-487.

DeFreitas, B ., & Schwartz, G. Effects of caffeine in chronic psychiatric patients. American Journal of Psychiatry, 1979, 136, 1337-1338.

Domino, E.F., & Lutz, M. P. Tolerance to the effects of daily nicotine on bar pressing behavior for water reinforcement. Pharmacology Biochemistry and Behavior, 1973, JL_, 445-448.

Driscoll, P., & Baettig, K. Selective inhibition by nicotine of shock- induced fighting in the rat. Pharmacology Biochemistry and Behavior, 1981, 1£, 175-179.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29

Eichelman, B., Orenberg, E., Hackely, P., & Barchas, J. Methyl xanthine- facilitated shock induced aggression in the ra t. Psychopharmacology, 1978, 56, 305-308.

Emley, G. S., & Hutchinson, R. R. Unique influences of ten drugs upon post-shock biting attack and pre-shock manual responding. Pharma cology Biochemistry & Behavior, 1983, JJ9, 5-12.

Estler, C. J. Effect of and -adrenergic blocking agents and parachlorophenylalanine on morphine and caffeine stimulated locomotion activity in mice. Psychopharmacology, 1978, 28, 261- 268. .

Falkeborn, Y., Larsson, C., h Nordberg. Chronic nicotine exposure in the rat: A behavioral biochemical study. Drug & Alcohol Dependence, 1981, 8, 51-60.

File, S. E., & Hyde, J. R. G. A test of anxiety that distinguishes between the actions of benzodiazepines and those of other minor tranquilisers and of stimulants. Pharmacology Biochemistry & Behavior, 1979, 11, 65-69.

Forrest, W. H., Bellville, J. W., & Brown, B. W. The interaction of caffeine with pentobarbital as a nighttime hypnotic. Anesthesiology, 1972, 36, 37-41.

Goldstein, A., Kaizer, S ., & Whitby, 0. Psychotropic effects of caffeine in man. Quantitive and qualitative differences assocaited with haabituation to coffee. Clinical Pharmacology and Therapeutics, 1969, 10, 489-497.

Greden, J. F. Anxiety or caffeinism: A diagnostic dilemma, American Journal of Psychiatry, 1974, 131, 1089-1092.

Greden, J. F., Fontaine, P ., Lubetsky, J ., & Chamberlin, K. Anxiety and depression associated with caffeinism among psychiatric inpatients. American Journal of Psychiatry, 1978, 135, 963-966.

Hansten, P. D. Drug Interactions. Philadelphia: Lea & Febiger, 1971.

Henry, J. P., & Stephens, P. M. Caffeine as an intensifier of stress- induced hormonal and pathophysiologic changes in mice. Pharmacology Biochemistry and Behavior, 1980, 13_, 719-727.

H ollister, L. E. Interactions of psychotherapeutic drugs with other drugs and with disease states in M. A. Lipton, A. DiMascio & K. F. K ill man. Psychopharmacology: A Generation of Progress. New York: Raven Press, 197S.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30

Holtzman, S. G. Complete reversible drug-specific tolerance to stimulation of locomotor activity by caffeine. Life Science, 1983, 33, 779-787.

Kallman, W. M. & Isaac, W. The effects of age and illumination on the dose-response c u rv e s for three stimulants. Psychopharmacologia, 1975, 40, 313-318.

Landis, J. R., Cooper, M . M ., Kennedy, T ., & Koch, G. G. PARCAT: A computer program fo r testing average partial association in three- way contingency t a b l e s . S ta tis tic a l Computing Section Proceedings of the American S tatistical AssociatioFT

Landis, J. R., Heyman, E . R., & Koch, G. G. Alternative tests for average partial a s s o c ia tio n in three-way contingency tables. International S tatistical Review, 1978, 46, 237-254.

Lasagna, L. Some ad verse interactions with other drugs. In M. A. Lipton, A. D iM arcio & K. F. K ill am. Psychopharmacology: A Generation of P ro g re s s . New York: Raven Press, 1978.

McNair, E. & Bryson, R . Effects o f nicotine on weight change and food consumption i n ra ts . Pharmacology Biochemistry & Behavior, 1983.

Melmen, K. L. & G ilm an, A. G. Drug interaction. In A. G. Gilman, L. S. Goodman & A. G ilm a n (6th E d .), Goodman and Gilman: The Pharmacological B a s is of Therapeutics. New York: Macmillan Publishing Co., I n c . , 1980.

Merkel, A. D ., Wayner, F . B ., Jolicoeur, F. G., & Mintz, R. Effects of caffeine adm inistration on food and water consumption under various experimental c o n d itio n s . Pharmacoloqy Biochemistry and Behavior, 1981, 14, 235-240.

Morrison, C. F., Goodyear, J. M. & S ellers, C. M. Antagonism by antimuscarinic and ganglion-blocking drugs of some of the behavioral effects of n ic o tin e . Psychopharmacol ogi a , 1969, 15_, 341-350.

Morrison, C. F ., & Stephenson. The occurrence of tolerance to a central depressant e ffe c t o f nicotine. British Journal of Pharmacoloqy, 1972, 45, 151-156.

N eil, J. F. Himmelhoch, J . M., M allinger, A. G., Mallinger, J. & Hanin, I . Caffeinism c o m p licatin g hypersomnia depressive episodes. Comprehensive P s y c h ia tr y , 1978, 19^ 337-385.

Quenzer, L. F. & Feldman, R. S. The mechanism of anti-muricidal effects of chlordiazepoxide, Pharmacology Biochemistry & Behavior, 1975, 3, 567-571.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31

Rail, I . W. Central nervous system stimulants. The Xanthines. In A. G. Gilman, L. S. Goodman A A. Gilman (6th ed.) Goodman and Gilman's The Pharmacological Basis of Therapeutics. New York: Macmillan Publishing Co., In c., 1980.

Sanger, D. J. Nicotine and schedule-induced drinking in rats. Pharmacology Biochemistry and Behaviors, 1978, :8 343-346.

Stolerman, I. Fink, R., A Jarvik, M. £. Acute and chronic tolerance to nicotine measured by activitv in rats. Psychopharmacologia, 1973, 30, 329-342.

Stolerman, I. P., Bunker, P., A Jarvik, M. E. Nicotine tolerance in rats; Role of dose and dose interval. Psychopharmacologi a , 1973, 30, 329-342.

Thethapandha, A. H. M., Maling, A Gilette, J. K. Effects of caffeine and theophylline on activity of rats in relation to brain xanthine concentration. Proceedings in Experimental Biology and Medicine, 1972, 582-586.

W aldbillig, R. J. Suppressive effects of intraperi.otoneal and intra- ventricular injections of nicotine on muricide and shock-induced attack on conspecifics. Pharmacology Biochemistry and Behavior, 1980, 12, 619-523.

Waldeck, B. Ethanol and caffeine: A complex interaction with respect to locomotor activity and central catecholamines. Psychopharmacologi a, 1974, 36, 209-220.

Waldeck, B. On the interaction between caffeine and barbiturates with respect to locomotor a ctivity and orain catecholamines. Acta Pharmacol et toxi:o! , 1975, ^6., 172-130.

Wayner, M. J., Jolicoeur, F. B., Ronceau, 0. 8., A Barone, F. C. Effects of acute and chronic administration of caffeine on schedule dependent and scheduled induced behavcor. Pharmacology Biochemistry & Behavior, 1976, 5_, 343-343.

Winstead, D. K. Coffee consumption among psychiatric inpatients. American Journal of psychiatry, 1975, 133, 1447-1450.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.