: Pathways to Addiction.

Chris Evans, PhD NIDA Center for the Study of Opioid Receptors and Drugs of Abuse (CSORDA), UCLA, California One side of the story

- Pain of all types is undertreated in our society. The pediatric and geriatric populations are especially at risk for undertreatment. Physicians’ fears of using opioid therapy, and the fears of other health professionals, contribute to this problem.

- Opioid analgesics are generally safe medications when prescribed with appropriate monitoring. There is very little if any evidence of organ damage from the long term therapeutic use of . With appropriate titration and stable dosing, tolerance develops to most of the side effects of opioid therapy, including cognitive impairment. Constipation is the most common persistent side effect and should be managed prophylactically.

Use of opioid analgesics for the treatment of chronic noncancer pain - A consensus statement and guidelines from the Canadian Pain Society 1998

John Liebeskind 1935-1997 The Other Side

Nonmedical New Users Past Year Nonmedical Use of Pain Relievers (% use 12 or Older, 02-04) 3 million of Psychotheraputics

2 million

1million

% US Population 5.68-7.00 0 3.78-5.67 2.61-3.75

1) New Nonmedical Prescription Pain Reliever users Outnumbered New Marijuana Users (2002-2004) 2) 2.7% of the population 12 and older in 03 used prescription psychotherapeutic medications nonmedically in the month prior to surveyed. This included 4.7 million using pain relievers (compares to 166,000 users). 3) Estimated 415,000 Americans received treatment for pain reliever abuse in the past year. 4) Past year abuse of Vicodin 3.0% among 8th-graders, 7.0 % among 10th-graders, and 9.7% among 12th-graders in 2006, (stable since ‘02). Despite a drop in past year abuse of OxyContin among 12th-graders in ‘06, abuse among 8th-graders nearly doubled since 2002 (1.3% in ‘02 - 2.6 % in ‘06) Data from the 2002, 2003 and 2004 National Surveys on Drug Use and Health POMC PROORPHANIN-FQ

Prohormone Convertases (PC’s) CPE and PAM

ACTH, MSH

ENDOMORPHINS? δ µ κ ORL-1 ?

MORPHINE, , ETORPHINE, , , , , HEROIN, (RARELY RECEPTOR SPECIFIC - Drugs are dirty) Morphine (surgery) Buprenorphine (addicts) Methadone (addicts) Oxy/hydrocodone (pain)

OH OH CH3O OXY (X=OH) HYDRO (X=H) CODONE O CH3-N-CH3 CH3 O O CH3 O

N-CH3 N- NCH3 CH2 X OH CH3O O HO-C-CH PERCOSET 3 PERCODAN OXYCODONE

C (CH3)3 OXYCONTIN VICODIN HYDROCODONE

Fentanyl (epidural, Moscow Siege Gas) selectivity O /Partial Activity at other receptors (NMDA) CH2CH2 NCCH2CH3 N Rate of onset/duration* Route of Administration Dependency/tolerance Activity at mu opioid receptors Mu Agonists: analgesia, constipation, reward, nausea, respiratory depression - gender specific Antagonists: aversive*, prevent reward Delta Agonists: not-rewarding, weak analgesia, seizure-inducing Antagonists: no obvious effects Kappa Agonists: aversive, hallucinogenic, analgesia Antagonists: potential antidepressants/relapse ORL-1 Agonists: Hyperalgesia* and block opioid analgesia Antagonists: no obvious effects Homologous recombination

Mu KO mice have no classical morphine effects (analgesia, respiratory depression, reward, immune modulation). No longer are alcohol, nicotine or THC rewarding! Reviews by Kieffer’s group Curr Opin Neurobiology, 2004 BUPRENORPHINE (κ antagonist, µ/δ /ORL-1 partial agonist) HAS NO EFFICACY IN MU RECEPTOR KO MICE

15

12 WT MuKO 9

6

3 Tail flick latency (sec) 0 Baseline 0.1 mg/kg0.3 mg/kg 1 mg/kg 3 mg/kg

Buprenorphine (s.c.) BUPRENORPHINE HAS INCREASED ANALGESIC EFFICACY IN ORL-1 RECEPTOR KO MICE ) c e

s Cut off

( WT WT

y ORL-1KO ORL-1KO c

n 12 12 e t a

l 9 9

k c

i 6

l 6 f

l i 3 3 a T 0 0 Baseline 0.1 0.3 1 3 Baseline Cont.+J-113397 Bup. (mg/kg s.c.) Bup. (0.3mg/kg s.c.)

ORL-1 Receptor KO Mice Courtesy of Hiroshi Takeshima, J-113397 Ivy Carroll ACUTE OPIOID EFFECTS Analgesia, Antitussive Constipation, Euphoria, Nausea*, Calming* codin Decreased Respiration ntin, vi oxyco ine morph heroin, r ula ell , c al ar ior ul av relapse lec eh o b ns ? m nd tio a ta ap ? ad

WITHDRAWAL

CHRONIC OPIOID EFFECTS Tolerance to acute effects, Hyperalgesia, Dysphoria, Anxiety, normalization of physiology & Sweating, Runny nose, Chills, drug/action psychology in presence of drug Diarrhea, Nausea associations Liking Wanting Taking the drug feels good The drug is desired for its - is rewarding and/or remembered effects (analgesia, satisfies the reasons for rewarding, calming, combating taking the drug. withdrawal, physiologic effect). In extreme cases this can become craving

Habit Taking the drug as a result of automatic response to a stimulus - after eating - smoke Stressed or anxious - drink or take a vicodin SYSTEM INTERDEPENDANCE FOR REWARD

Morphine/Heroin THC CB-1 Nicotine ACh Alcohol GABA/NMDA Mu Opioid Receptors

Kappa Mu receptor CB-1 and NK-1 receptor activation by receptor activation by activation endogenous opioids endogenous ligands

Antagonism

Activation of Mesolimbic AVERSION Dopamine system REWARD (CPP) ) Msethadone Maintained Patients are Hyperalgesic d n in Cold Pressor Test. o COLD PRESSOR TEST ) 70 c s d n

e o 60 c e

s s Control ( 50 r

( e Control t Methadone a MM

w 40 Maintained

d e l o

c 30 m- ••• *p=0.023 e *** c

i ***p<0.0001 i 20 n i *** p<0.0001 T e ••• m

i 10 ••• T * 0 Detection Tolerance Detection Tolerance Pain Pain Pain Pain Det e c0ti oHnOURToSlerance Dete c3ti oHn OURTSolerance 3hr after Methadone

Slide kindly provided by Walter Ling, UCLA Hyperalgesia Following Chronic Morphine (TAD)- Pain Paradigm Specific

l A B a ) w 5 30 150’ post-morphine s a (

r *

d y )

* 25 h c s 4 t ( i n

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c l a

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t a e a

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l 10

t e o s 1 a h 5 b 0 0 saline chronic saline chronic control morphine control morphine *

48ºC FORSKOLIN-STIMULATED cAMP ACCUMULATION FOLLOWING ACUTE AND CHRONIC OPIOID TREATMENT - CYCLASE SUPERSENSITIVITY

400

E

G Acute:

N 300 opiod +

A

H forskolin

C

%

] 200 Chronic: 24h

P

M opioid then

A RTI- c wash out [ 100 1d +forskolin

0 Control 0.1nM 1nM 10nM 100nM

[DAMGO] MU OPIOID RECEPTOR COMPLEX (diversity)

REGULATION TRAFFICKING COMPLEX DETERMINATION 5+proteins 2+proteins 1. Cellular Proteome SIGNALING 2. Mu receptor alternative splicing 8+proteins 3. Cellular Compartment 4. Oligomerization (Hetro/Homo) 5. The Receptor Activation State 6. History of Receptor/Environment 100+proteins 100+proteins

100+proteins

Arrestins/G-proteins/GRK’s/Src’s/RGS’s FLAG & MOR-C12 STAINING OF 293-CELLS TRANSFECTED WITH MU RECEPTORS

CONTROL ETORPHINE DAMGO ETOR/NALOX MORPHINE

(100nM) (100nM) (100nM/10µM) (20µM) Desensitized Receptor Agonist Binding

Re-sensitized P P g P Receptor lin Signaling P na Si Sig gna ling

GRK 2 (1-6) Beta-arrestin 1-2 (cSrc) Phosphorylation

Recruitment of

Recycling (µ) Clathrin

P P

Lysosomes Downregulation (δ)

Endosome P Uncoating of

P CCV and Fusion with Endosome Severing of CCV by Dephosphorylation Dynamin Mouse Dorsal Root Ganglion Cells Morphine DAMGO Express mu and alpha2A receptors (No inMtoerrpnhianleization) (InteDrAnMaGliOzation)

0 min 0 min

30 min 4 hr

4 hr 4 hr+PD16

µ α2A Merged µ α2A Merged µ α2A Merged

DAMGO 60 Morphine # 50 -Blocking internalization with the P38 inhibitor 40 PD169316 blocks calcium signaling 30 * desensitization via DAMGO but not morphine * * - The alpha 2A receptor internalizes with 20 DAMGO treatment - blocked by PD169316 10 11 14 7 19 9 21

Calcium Current Inhibition(%) 0 0 hr 4 hr 4 hr + PD16 Opioid Pretreatment Time

Tracy Xie CSORDA Lab 2006, submitted Clonidine and DAMGO but not morphine induce both mu and alpha2A internalization and desensitization.

DAMGO Clonidine

0 min 0 min

4 hr 4 hr

µ α2A Merged µ α2A Merged

DAMGO Morphine 40 DCAhMGaOl ltesnt ge ChMoarplhlienen tegste 60 Clonidine Challenge # # 30 50 ** # 40 20 30 *

20 10 * 10 Calcium Current Inhibition(%) 12 7 12 11 0 6 62 18 8 10 9 7 Calcium Current Inhibition(%) 0 0 hr 4 hr 4 hr+CT 0 hr 4 hr 0 hr 4 hr 4 hr +Yoh 0 hr 4 hr 4 hr +Yoh DAMGO Pretreated Morphine Pretreated Clonidine Pretreated P38 inhibition blocks mu internalization but not Clonidine-induced alpha2A internalization and desensitization.

4 hr Clonidine Treatment + P38 inhibitor PD169316 Clonidine test

20

10 ** **

21 14 14 µ α2A Merged 0 Calcium Current Inhibition(%) 0 hr 4hr 4 hr+PD16 Clonidine Pretreatment

DAMGO Clonidine Challenge 25 Challenge Summary # 60 20 -Functional implications of mu and Alpha2A ## adrenergic association in endogenously 15 expressing nociceptive neurons 40 ** -Mu agonist specific cross-desensitization 10 of Alpha2A adrenergic signaling 20 ** 5 Calcium Current Inhibition(%) Calcium Current Inhibition(%) 62 18 10 12 8 17 0 0 None D D None Clo Clo Pretreat Pretreat PD16 PD16 Role of Opioid System in Habit and Goal-Directed Behaviors

Mu receptor knockout mice. - Lack reward-directed behaviors to many rewarding drugs - Phenotype of sibling response to mother absence

Sugar ? Sugar

Sugar Sugar Sugar noyes noyes Sugar Sugar

graingrain grain

grain grain grain grain Devaluation Acquisition Extinction Punishment 14 4.0 7 Non n i 3.5 DEV 12 m 6 r e n i

p 3.0

m 10 s

5 r e e s 2.5 s p dev WT

8 e

s 4

r non s p

2.0 e r r MU -/- dev e

p 6 MOR

3

v non r

WT e 1.5 e L v

e 4 2

L 1.0

2 0.5 1

0 0.0 0 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 45 50 1 2 3 4 5 MOR WT 1st 10 rewards Blocks of 5 rewards 4-min bins

Maidment and Balleine Labs CSORDA 2006 knockout mice.

? Sugar Sugar Sugar Sugar Sugar noyes noyes Sugar Sugar

graingrain grain

grain grain grain grain

sugar sugar grain No food Sugar piles up grain grain sugar in food tray in 1h 10’ 10’ Enk-KO trials Summary

Mu -/- appear to have a problem with retrieving reward value: They are sensitive to changes in value but are unable to retrieve changes in a test of free recall but can when the outcome is delivered. pENK -/- are unable to control their actions when faced with lack of salience. They appear to have a specific problem with goal-directed actions. Performance is likely controlled by a stimulus- response process and is habitual.

Retrieved value: Extinction Punishment

100 Devalued 100 Devalued Valued 90 Valued 90 80 80 g n i 70 70 d n n o i o t 60 p 60 a s u l e r

a 50 50 l v a e t

o 40 D 40 t

% 30 30 20 20 10 10 0 0 D V D V D V D V D V D V

WT Mu pENK WT Mu pENK 1) +NK-1/CB-1 antagonist 2) Slow on and off rate +/- 3) Partial agonist - safety Kappa antagonists? REWARD/ANALGESIA (JD-Tic)  PLASTICITY   ENVIRONMENT RELAPSE  DRUG ACCESS

Adaptive Changes. Tolerance. Salience for rewards likely disrupted  Partial Agonists? Mu-agonists that show selective signaling and trafficking



WITHDRAWAL Symptom alleviation NK-1 antagonist hyperalgesia