Jpn. J. Oral Biol., 39: 284-296, 1997.

ORIGINAL

The paradoxical effects of the dibenzodiazepine derivative, clozapine, on auto- nomic stimulating drug-induced salivary responses in mice

Toshiko Ogawa

Department of Dental Pharmacology, School of Dentistry, Iwate Medical University (Chief: Prof. Tadanobu Itoh) 1-3-27, Chuodori, Morioka 020, Japan

〔Recieved on March 3, 1997; Accepted on May 19, 1997〕

Key words: clozapine/salivary response/neurotransmitter/salivary gland/brain

Abstract: The effects of the dibenzodiazepine derivative, clozapine, on the salivary responses induced by autonomic stimulating drugs, and also on the levels of monoamines and ACh in the salivary glands and brains in mice were examined. The salivary responses induced by pilocarpine (0 .8mg/kg, s.c.), phenyle- phrine (5mg/kg, s.c.), isoproterenol (0.4mg/kg, s.c.) and dopamine (10mg/kg, s.c.) reached a maximum level 20min after administration, but decraesed thereafter and disappeared after 90min . Although clozapine (3, 10 and 30mg/kg) alone had no influence on salivary secretion in anaesthetized and non-anaesthetized mice, clozapine inhibited the pilocarpine-and dopamine-induced salivary responses in a dose-dependent manner. The phenylphrine-induced salivary response was increased with clozapine at 3mg/kg , and de- creased at doses of 10 and 30mg/kg. However, clozapine had no influence on the isoproterenol-induced salivary response. The salivary responses induced by autonomic stimulating drugs showed the lowest level when clozapine (10mg/kg) was given 1 or 2 hours before the administrations . In mice treated with clozapine (10mg/kg), the ACh and DA levels decreased in the salivary glands, whereas the levels of monoamine related substances increased in the brain. These results suggest that the biphasic action of clozapine on the

α-adrenergic agonist-induced salivary response is related to the paradoxical symptoms of hypo-and hyper -salivation often observed in patients receiving clozapine .

抄 録:Dibenzodiazepine誘 導 体clozapineの 自律 神 経 作 動 薬 に よ る誘 導 唾 液 分 泌 反 応,な らび に 唾 液 腺 と脳 内 モ ノ ア モ ン お よ びACh含 量 に及 ぼ す 影 響 に つ い て マ ウ ス を 用 い て 検 討 し た。Pilocarpine (0 .8mg/kg, s.c.),

phenylephrine (5mg/kg, s.c.), isoproterenol (0.4mg/kg, s.c.)ま た はdopamine (10mg/kg, s.c .)に よ る 誘 導

唾 液 分 泌 反 応 は 投 与20分 後 に 最 大 値 を 示 し,そ の 後 減 弱 し,90分 後 に は 消 失 し た 。Clozapine (3 , 10, 30mg/ kg)そ れ 自身 は無麻酔下 または麻酔下のマウスの唾液分泌反応には影響を及ぼさなかったが ,pilocarpineお よ び dopamineの 誘 導 唾 液 分 泌 反 応 を 用 量 依 存 的 に 抑 制 し,phenylephrineの 反 応 で はclozapineの 低 用 量 で 促 進 ,高 用 量 で 抑 制 し,isoproterenolの 反 応 に は 影 響 を 及 ぼ さ な か っ た 。 自 律 神 経 作 動 薬 に よ る 誘 導 唾 液 分 泌 反 応 は , clozapineが1ま た は2時 間 前 後 に 投 与 さ れ た 場 合 に,そ の 反 応 の 抑 制 の 程 度 は 最 も強 か っ た 。Clozapine (10 mg/kg)投 与 マ ウ ス に お い て,唾 液 腺 内 のAChお よ びDA含 量 は低 下 した が ,脳 内 の モ ノ ア ミ ン関 連 物 質 含 量 は 増 大 を示 し た 。以上 の こ とか ら,交 感 神 経 α-作 動 薬 に よ る誘 導 唾 液 分 泌 反 応 に 対 す るclozapineの 二 相 性 作 用 が , clozapineを 投 与 さ れ た 患 者 に お い て,し ば し ば観 察 され る 唾 液 分 泌 の 減 少 あ る い は過 多 の 奇 異 な 症 状 に 関 連 性 が あ るか も し れ な い こ とが 示 唆 さ れ る。 Toshiko Ogawa: The paradoxical effects of clozapine 285

and brains were determined and discussed.

Introduction

Materials and Methods

Clozapine of dibenzodiazepine derivatives is an atypical antipsychotic drug with pharmacological 1. Animals properties that are different from typical antipsy- Male ddY mice, 5weeks old, weighing 28～32g, chotic drugs such as chlorpromazine and were purchased from the Shizuoka Laboratory Ani- haloperidol1～7). Recent studies have shown that mal Center (Japan). Animals were housed, in groups clozapine has an antagonistic effect on muscarinic of 10-12, in a room maintained under conditions of

acetylcholine receptors (mAChr)7,8), α-adrenergic controlled lighting (a 12-hour light/dark cycle), tem- receptors9), serotonin receptors10), dopamine perature (23±2℃) and humidity (55±5%) with free receptors7,11,12) and histamine receptors13). In addition, access to standard chow (Oriental Yeast Co.) and

it was found that clozapine has no ability to induce the water. All experiments using animals were performed

development of catalepsy, increase the levels of serum according to the 'Guide for Care and Use of Labora-

prolactin14), or inhibit the stereotyped behaviors in- tory Animals' at Iwate Medical University. duced by apomorphine and amphetamine14).

On the other hand, it is suggested that clozapine has 2. Drugs and administrations

astrong clinical antipsychotic effect on patients with Clozapine hydrochloride used in the present experi- schizophrenia3,6), and that it is especially effective in ment was supplied from the SANDOZ Pharmaceutical

improving the following symptoms: positive symp- Co. (Switzerland). Fig. 1 shows the chemical structure

toms such as hallucinations and delusions of types of clozapine.

found in patients with schizophrenia, and negative Chemicals were purchased from the following symptoms such as the showing of no emotions and sources: pilocarpine hydrochloride, dopamine (DA)

secession from society3,6). However, side effects such hydrochloride, Na2EDTA, N a2HPO4, H3PO4 and

as sedation, tachycardia, hypotension, dizziness and tween 80 from Kanto Chemicals; phenylephrine

aglanulocytosis often develop in patients receiving hydrochloride from Kowa Chemicals; isoproterenol

clozapine1,15,16), though extrapyramidal symptoms and hydrochloride from Nikken Chemicals; 3-methoxy-4 -hydroxyphenylglycol (MHPG) hemipiperazine salt tardive dyskinesia are absent1). ,

Because it has an antagonistic effect on the and homovanillic acid (HVA) from Sigma Chemi-

cholinergic7,8,17) and adrenergic9) nervous systems, it is cals; 3, 4-dihydroxyphenylacetic acid (DOPAC), 5-

generally accepted that clozapine causes hyposaliva- hydroxyindoleacetic acid (5-HIAA), sodium he-

tion and dry mouth18). It is also reported that in ptanesulfonic acid, and sodium octanesulfonic acid

addition to this inhibitory effect, the agent induces from Aldrich Chemicals; norepinephrine (NE) bitar-

ptyalism by stimulating salivary secretion6,19,20). How- trate, serotonin (5-HT) creatine sulfate, acetyl- ever, the mechanism of this paradoxical action (bi- phasic action: inhibition and stimulation) of clozapine on the response to salivary secretion is not entirely clear.

In the present study, to clarify the biphasic effects of clozapine on salivary secretion, the responses to salivation induced by autonomic stimulating drugs in mice receiving clozapine were examined phar- macologically. Based on the influence of clozapine on neurotransmitters, the levels of monoaminergic and cholinergic neurotransmitters in the salivary glands Fig. 1 Chemical structure of clozapine. 286 Jpn. J. Oral Biol., 39: 284-296, 1997.

choline (ACh) perchloride, tetraethylammonium chlo- paper,No. 2),and moved to a fresharea on thefilter ride, 70% perchloride acid and urethane from Wako paper every10min for90min. Pure Chemicals. Ethylhomocholine was synthesized in The sizeof thesaliva-stained spot on thefilter was our laboratory according to the method of Potter et determinedusing a ScanJetIIc Scanner and an NIH al.21). All other reagents and solvents were of special image analyzer(Version 1.55, Wayre Rasband,NIH,

grade for use in high performance liquid chromatogra- USA) connectedto a Macintoshcomputer (Centris

phy (HPLC). 650).The amount of salivasecreted per unittime was

Clozapine was suspended in a 0.5% tween 80 solu- evaluated.The valuesobtained over the90-min obser- tion immediately before every administration, and the vationperiod were compared with thecontrol values. dosages were 3, 10 and 30mg/kg. In the experiments Salivationexperiments were carriedout in a room with mice pretreated with and without sialogogues, with similarconditions of light,temperature and clozapine (3, 10 and 30mg/kg) was injected 30min humidityto the breedingroom. In addition,mice of before measuring salivary secretion. In the experi- similarage, body weight,and generalcondition were ments on the influence of clozapine on the difference used in the experiments,and measurements were of administration time, clozapine (10mg/kg) was performed between10:00 and 15:00 (once in the injected 30min, and 1, 2, 3, 5, 12 and 24 hours before morning and once in the afternoon),taking the cir- the administration of sialogogues. In the experiments cadianrhythm inthe salivation of mice intoconsidera- for measurement of the monoaminergic and choliner- tion.

gic neurotransmitter contents in the salivary glands

and brains of mice receiving clozapine (10mg/kg) , 4. Tissue preparationof salivaryglands and clozapine was injected 90min before microwave irra- brainsof mice diation (the time when indicated salivary responses Ninety min afterthe administrationof either10 where at the lowest level). mg/kg of clozapineor 5ml/kg of a 0.5% tween 80

Sialogogues used in the present experiment were; solution,each animalwas irradiatedby a microwave

pilocarpine (0.8mg/kg) of partial muscarine agonists beam (5kW, 0.7sec.,TMW-6402C, Toshiba,Japan) in the parasympathomimetics, phenylephrine (5mg/ focusedon the head. kg) of α1-receptor agonists and isoproterenol (0 .4 1) Tissueextraction mg/kg) of β-receptor agonists in the sympath- Aftermicrowave irradiation,the salivaryglands of omimetics, and dopamine (10mg/kg) of dopamine the right side were carefully removed and the subman- receptor agonists in the dopaminomimetics. Control dibular, sublingual and parotid glands dissected out . animals were treated with 5ml/kg of a 0.5% tween The brain was removed from each mouse and dissect-

80 solution. All agents were subcutaneously adminis- ed into four regions: cerebral cortex , hypothalamus, tered. corpus striatum and hippocampus , according to a

modified method of Glowinski and lversen24) . Isolated 3. Measurement of saliva tissues from the salivary glands and brain were quick-

Measurement of saliva was performed using the ly frozen on dry ice , and then weighed and stored in a method of Murai et al.22), a somewhat modified ver- 1.5ml Eppendorf microtube at-80℃ until prepara-

sion of Richter's method23). The mice were injected tion. subcutaneously with urethane (1.0g/kg body 2) Tissue preparation weight), and their heads and limbs were fixed with After thawing, the isolated tissues were homogen- fine tape on a special fixing plate. Sialogogues were ized with an ultrasonic cell disruptor (Model 200 , injected subcutaneously into the cervical back 30min Branson, USA) in 300～400μl of an ice-cooled 0 .05M after the injection of urethane. The fixed mice were perchloric acid solution containing 0.1mM Na2EDTA then immediately placed, face down on a sloping for measurement of monoamines . However, for mea- plastic plate covered with filter paper (TOYO Filter surement of ACh, 750, 500, 750 and 300～400μl of an Toshiko Ogawa: The paradoxical effects of clozapine 287

ice-cooled 0.1M perchloric acid solution containing EICOM, Japan), a catecholamine-trap column (CA-

0.1mM Na2EDTA and 100μM ethylhomocholine Trap, EICOM, Japan), a guard column (Eicom Pre-

(internal standard for ACh assay) were added to pak, EICOM, Japan), an electrochemical detector homogenize the submandibular, sublingual and par- (Model VMD-5000, Yanagimoto, Japan), a platinum otid glands and the brain, respectively. working electrode (WE-PT, +0.5V, EICOM, Japan),

The homogenates were centrifuged at 12,000g for an integrator (Model C-R 3A, Shimadzu, Japan), and

20min at 4℃. The clear supernatant was filtrated a column jacket connected to a thermostatic water- through a 0.45μm filter (Type, HV. Nihon Millipore, bath (Model UC-65, Tokyo Rika Kikai, Japan). The

Japan) and stored at-80℃ until assay. mobile phase was a 0.06M phosphate buffer (pH 8.3)

containing 0.01% tetraethylammonium chloride,

5. Chromatographic conditions for monoamines 0.3% octanesulfonic acid sodium and 0.1mM Na2-

and related substances EDTA. The conditions of measurement were set at a

Monoamines and related substances in the salivary flow-rate of 1.9ml/min with a temperature of 35℃

glands and brain were measured by an HPLC-ECD for the salivary glands, and at the 2.0ml/min and

system according to the method described by Murai et 33℃ for the brain.

al.25,26).

The HPLC-ECD system consisted of a solvent 7. Statistical analysis

delivery pump (Model L-6000, Hitachi, Japan), an The results obtained were expressed as the mean analytical column (WH-C 18, Hitachi, Japan), a values ±S.E. Statistical analysis was performed with

guard column (Eicom Prepak, EICOM, Japan), a ANOVA (one tailed) and Duncan new multiple range

coulometric electrochemical detector (ESA, 5100A, tests.

MA, USA), an integrator (Model C-R 6A, Shimadzu,

Japan), and a column jacket connected to a thermo- Results static waterbath (Model UC-65, Tokyo Rika Kikai,

Japan). The mobile phase was a 0.02M acetic acid 1. Effect of clozapine alone on the response to

sodium/0.0125M citric acid buffer (pH 4.0) contain- salivary Secretion in mice

ing 7.4% methanol, 0.045% heptanesulfonic sodium In anaesthetized and non-anaesthetized mice, and 0.1mM Na2EDTA. The conditions for measure- clozapine (3, 10 and 30mg/kg) alone exerted no influ-

ment of the salivary glands and brain were; a flow- ence on salivary secretion.

rate of 2.3ml/min and a temperature of 40℃.

Substances measured were norepinephrine (NE) 2. Effects of clozapine on the piloearpine-,

and its metabolite 3-methoxy-4-hydroxyphenyl- phenylephrine-, isoproterenol-and dopamine glycol (MHPG), dopamine (DA) and its metabolites -induced salivary responses

3, 4-dihydroxyphenylacetic acid (DOPAC) and 1) Pilocarpine-induced salivary response (Fig. 2) homovanillic acid (HVA), and serotonin (5-HT) and Pilocarpine-induced salivation reached a maximum its metabolite 5-hydroxyindoleacetic acid (5-HIAA). value 20min after pilocarpine administration, de-

creased with time thereafter, and disapPeared after 90

6. Chromatographic conditions for ACh min. Such a salivary response was inhibited signifi-

ACh in the salivary glands and brain were measured cantly depending on the dose of clozapine. However, by an HPLC-ECD system according to the method maximum values of all responses were observed 20 described by Murai lt al.25,26). min after pilocarpine administration. Furthermore,

The HPLC-ECD system consisted of a solvent the total volume of saliva induced by pilocarpine delivery pump (Model L-5000, Yanagimoto, Japan), treatment was reduced by 30% in mice receiving 3 an analytical column (AC-GEL, EICOM, Japan), an mg/kg clozapine, 70% in those receiving 10mg/kg immobilized enzyme column (AC-Enzympak, clozapine and 75% in those receiving 30mg/kg 288 Jpn. J Oral Biol., 39: 284-296, 1997.

Fig. 2 Effect of clozapineon the response to pilocarpine-inducedsalivation.

clozapine. mum value 20min after isoproterenol administration,

2) Phenylephrine-induced salivary response (Fig. decreased with time thereafter, and disappeared after

3) 90min. No change in the salivary response and the

Phenylephrine-induced salivation reached a maxi- total volume of saliva produced was observed in mice

mum value 20min after phenylephrine administration, receiving 3, 10 and 30mg/kg clozapine which was

decreased with time thereafter, and disappeared after similar to the control.

90min. The response to phenylephrine-induced saliva- 4) Dopamine-induced salivary response (Fig. 5)

tion in mice treated with clozapine at 3mg/kg was Dopamine-induced salivation reached a maximum

significantly decreased compared to the control 10 value 20min after dopamine administration , de- and 20min after phenylephrine administration. This creased with time thereafter, and disappeared after 90

response reached a maximum value 30min after min. All dopamine-induced salivary responses in mice

phenylephrine administration, and decreased with treated with clozapine at 3, 10 and 30mg/kg showed a

time thereafter. However, the total volume of saliva significant decrease. However, maximum values of all

during phenylephrine-induced salivation in mice treat- responses were observed 20min after dopamine ed with clozapine at 3mg/kg increased significantly administration. Furthermore, dopamine-induced compared with the control. On the other hand, in mice salivation decreased significantly (by 40～55%) for receiving 10 and 30mg/kg clozapine, the phenyle- all doses of clozapine. phrine-induced salivary response decreased signifi- cantly, and the total volume of saliva was reduced by 3. Effectsof pretreatmenttime of clozapineon 70～80%. the sialogogue-inducedsalivary responses 3) Isoproterenol-induced salivary response (Fig. Salivationinduced by sialogogueswas investigated 4) in mice thathad 10mg/kg clozapineadministered at a

Isoproterenol-induced salivation reached a maxi- fixedtime. Toshiko Ogawa: The paradoxical effects of clozapine 289

Fig. 3 Effect of clozapine on the response to phenylephrine-induced salivation.

Fig. 4 Effect of clozapine on the response to isoproterenol-induced salivation. 290 Jpn. J. Oral Biol., 39: 284-296, 1997.

1) Response to pilocarpine-induced salivation in mice pretreated 5 and 12 hours before phenyle-

Fig. 6 (pilocarpine) shows the influence of time of phrine administration, the effect was significantly

pretreatment with clozapine on the response to saliva- weakened, and the total amount of the phenylephrine

tion induced by pilocarpine. Salivation was reduced by -induced salivation was reduced by 90% compared

15～35% in mice receiving clozapine 30min, and 1, 2, with the control. Moreover, in mice receiving

3 and 5 hours prior to pilocarpine administration clozapine 24 hours before phenylephrine administra-

compared with the control. The smallest reduction, tion, the level of phenylephrine-induced salivation was

about 15%, was observed in mice receiving clozapine similar to that of the control.

2 hours before pilocarpine administration. However, 3) Response to isoproterenol-induced salivation

in mice pretreated 12 hours before pilocarpine admin- Pretreatment with clozapine had no affect on the istration, the effect of clozapine on the salivary response to isoproterenol-induced salivation (Fig. 6, response was significantly weakened, and salivation isoproterenol). was reduced by 81% compared with the control . 4) Response to dopamine-induced salivation

Moreover, in mice receiving clozapine 24 hours before Fig. 6 (dopamine) shows the influence to time of pilocarpine administration, the level of pilocarpine- pretreatment with clozapine on the response to induced salivation was similar to that of the control . dopamine-induced salivation. Salivation was reduced

2) Response to phenylephrine-induced salivation by 20～53% in mice receiving clozapine 30min, and 1,

Fig. 6 (phenylephrine) shows the influence of time 2 and 3 hours prior to dopamine administration of pretreatment with clozapine on the response to compared with the control. However, in mice receiv- phenylephrine-induced salivation. Salivation was ing clozapine 5 and 12 hours before the administration, reduced by 25～53% in mice receiving clozapine 30 the effect of the salivary response was significantly min, and 1, 2 and 3 hours prior to phenylephrine weakened, and 24 hours before dopamine administra- administration compared with the control. However , tion the level of dopamine-induced salivation was

Fig. 5 Effect of clozapine on the response to dopamine-induced salivation . Toshiko Ogawa: The paradoxical effects of clozapine 291

Fig. 6 Effects of pretreatment time of clozapine on the response to sialogogue-induced salivation.

similar to that of the control. was performed 90min afteradministration of 10mg/ kg clozapine,under the same conditionsas for the 4. Effects of clozapine on the levels of measurement of monoamine relatedsubstances in the monoamines in the salivary glands salivaryglands. The ACh levelsin the submandibular, Measurement of levels of monoamines in the sali- sublingualand parotid glands were significantlyde- vary glands was performed 90min after administra- creased compared with the control (Table 1). tion of 10mg/kg clozapine with reference to the influ- ence of time of pretreatment with clozapine. The 6. Effects of clozapine on the levels of levels of NE and 5-HT in the submandibular, sublin- monoamines and itsrelated substances, and of gual and parotid glands, did not differfrom that of the ACh in the brain control (Table 1). However, the DA levels in the Measurements of brain neurotransmitterswere submandibular and sublingual glands, but not in the performed under the same conditionsas the salivary parotid gland, showed a significantdecrease compar- glands. ed with the control. 1) Levels of brain monoamine relatedsubstances (Table 2) 5. Effects of clozapine on the levels of ACh in (1) Cerebral cortex: The levels of MHPG, the salivary glands DOPAC, HVA and 5-HT were significantlyincreased Measurement of levelsof ACh in the salivary glands compared with those of the control. 292 Jpn. J. Oral Biol.,39: 284-296,1997.

Table 1 Levels of monoaminergic and cholinergicneurotransmitters in the salivaryglands of mice treatedwith clozapine

Table 2 Levels of monoaminergic and cholinergic neurotransmitters in the brain of mice treated with clozapine Monoaminergic neurotransmitters Toshiko Ogawa: The paradoxical effects of clozapine 293

(2) Hypothalamus: The levelsof MHPG, DOPAC the anticholinergic action of clozapine7,8,18,27), the and HVA were significantlyincreased compared with blockade of D2-receptors7,11,12,14) and the disruption of those of the control,but the levelsof 5-HT and 5- the monoaminergic nervous systems29,30).

HIAA showed no change. Salivation induced by phenylephrine, an α-adrener-

(3) Corpus striatum: The levelsof MHPG, DA, gic receptor agonist, and also isoproterenol, an β-

DOPAC, HVA, 5-HT and 5-HIAA were significantly adrenergic receptor agonist, were similar in terms of

increasedcompared with those of the control. the time course of the response to pilocarpine-induced

(4) Hippocampus: The levels of MHPG, DA, salivation, but the amount of saliva secreted was

DOPAC, HVA and 5-HT were significantlyincreased lower than that induced by pilocarpine. These

compared with those of the control,but the 5-HIAA responses reached a maximum value 20min after

levelsshowed no change. administration of the agents, after which phenyle-

2) Levels of brain ACh phrine showed a rapid reduction and isoproterenol a In the cerebral cortex, hypothalamus, corpus slow reduction. Such a difference in the response

striatumand hippocampus the ACh levelsshowed no patterns may be due to the different mode of action of

change (Table 2). both agents. The response to phenylephrine-induced

salivation in mice treated with clozapine at 3mg/kg

Discussion increased significantly, and in mice treated with

clozapine at 10 or 30mg/kg decreased significantly,

Among patientsreceiving clozapine of dibenzodi- compared with non-treated mice. Thus, clozapine azepine derivatives,the symptoms of dry mouth in- displays dosage-related biphasic activity: stimula-

duced by hypo-salivation2,7,9,17,18)and/or ptyalism in- tion at low dosage and inhibition at high dosage in

duced by hyper-salivation6,19,20)are often observed. To phenylephrine-induced salivary response. This sup-

clarifythese paradoxical symptoms, the effectsof ports the theory that clozapine has an inhibitory effect

clozapine on the response to salivationinduced by on α-adrenergic receptors9). However, that a low dose sialogogueswere examined, because clozapineitself of clozapine increases the phenylephrine-induced sali- had no influenceon salivationin anaesthetizedor non- vary response in mice is not clear from the present anaesthetizedmice. results. On the other hand, clozapine had no influence The response to salivationinduced by pilocarpine, on the isoproterenol-induced salivary response. an mAChr agonist,reached a maximum value 20min The total amount of saliva secreted and the afteradministration, decreased with time thereafter, response pattern to dopamine were similar to those of

disappeared after 90min, and was inhibitedsignifi- phenylephrine-induced salivation. However, indepen-

cantly depending on the dose of clozapine.These dent of the dosage, clozapine significantly inhibited

findingssupport previousresults that clozapine blocks the dopamine-induced salivary response compared

mAChr7,8,18,27).However, Zom et al.20)reported that with the control. These findings reflect the blocking of clozapine stimulated M4-receptors of a mAChr dopaminergic receptors by clozapine7,11) and are in subtype, whereas Cawiey et al.28)reported that agreement with reports by Meltzer31) and Ferris et clozapinehad no influenceon mAChr. Thus, because al.32). clozapinedisplays various effects: stimulation, inhibi- Furthermore, in the experiments on the effects of tion or no influenceon mAChr itsmode of action on pretreatment time of clozapine on the response to the cholinergicnervous system is not uniform. How- salivation induced by pilocarpine, phenylephrine and ever,in the present study,clozapine showed an anti- dopamine, responses to salivation were of a similar cholinergiceffect on the pilocarpine-inducedsalivary pattern, except that induced by isoproterenol, i.e., response.Moreover, because extrapyramidal symp- when clozapine was administered 30min, and 1, 2 and toms did not develop in patients treated with 3 hours before the sialogogues, the responses to saliva- clozapine,it was consideredthat thiswas caused by tion induced by the sialogogues decreased significant- 294 Jpn. J. Oral Biol., 39: 284-296, 1997.

ly compared with the controL In addition, the levels of induced a decrease in the salivary glands. These

response were markedly lowered when clozapine was results suggest that there is a difference in the mode

administered 1 and 2 hours before the sialogogues. of action of clozapine on the neurotransmitters in the

Moreover, the responses to phenylephrine-and peripheral and central nervous system. However, dopamine-induced salivation in mice pretreated 5 because no paradoxical effects of clozapine on neur-

hours before clozapine showed a pattern similar to the otransmitters in the peripheral and central nervous

control, whereas the pilocarpine-induced salivary systems were observed, the relationship between the

response was maintained in the inhibited state. The paradoxical effects of clozapine on salivary response

difference in these responses to salivation may be due and the changes of the neurotransmitters remains

to different interactions between clozapine and the unclear.

sialogogues. In addition, in response to salivation

induced by mAChr agonist, duration of inhibition was Acknowledgements long, while in responses to salivation induced by α-

adrenergic and dopaminergic agonists, duration was I express my sincere thanks to Professor T. Itoh, short. However, clozapine had no influence on the Department of Dental Pharmacology for giving me

response to salivation induced by β-adrenergic the opportunity to initiate the present study and for

agonist. his kind guidance and suggestions. I also wish to thank

It is well known that salivary secretion is mainly Assistant Professor S. Murai, Dr. H. Saito and staff

regulated by cholinergic and adrenergic nervous sys- members of the Department of Dental Pharmacology,

tems which are distributed to the salivary glands33). for their encouragement and helpful advice.

Thus, the levels of monoamine related substances and

ACh, which influence the autonomic nervous systems, References

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