Transcript The Effect of Alcohol on Brain Reward

Effects of Alcohol on
Brain Reward
C.J. Malanga, MD, PhD
The University of North Carolina at Chapel Hill
January 6, 2009
Background:
Prenatal Cocaine Exposure in the Mouse
• Timed-pregnant white Swiss-Webster dams
• Injected b.i.d. from E8-E18
–
–
–
–
COC40:
SAL:
COC20:
SPF:
40 mg/kg/d, s.c. divided b.i.d.
Vehicle-injected controls
20 mg/kg/d, s.c. divided b.i.d.
Saline pair-fed nutritional controls
• Cross-fostered on P0 to non-exposed,
matched-parity black Swiss-Webster dams
• One pup per litter of each gender used for
experiments (“litter effects”)
– Holson and Pearce, Neurotoxicol Teratol 14(3), 1992
Mice exposed to cocaine in utero
1.
2.
3.
4.
5.
6.
… habituate less to novelty/injection stress than nonexposed controls (Guerriero et al., 2005);
… demonstrate less locomotor sensitization to repeated
psychostimulant administration than gestational controls
(Crozatier et al., 2003; Guerriero et al., 2005);
… demonstrate less conditioned place-preference to
cocaine than controls (Malanga et al., 2007a);
… are more likely to acquire cocaine self-administration
than controls (Rocha et al., 2002);
… self-administer more cocaine than controls (Rocha et
al., 2002);
… demonstrate more sensitization of dopamine release
in the nucleus accumbens after chronic cocaine
administration than gestational controls (Malanga et al.,
submitted)
Mice exposed to cocaine in utero
1.
2.
3.
… habituate less to novelty/injection stress than nonexposed controls (Guerriero et al., 2005);
… demonstrate less locomotor sensitization to repeated
psychostimulant administration than gestational controls
(Crozatier et al., 2003; Guerriero et al., 2005);
… demonstrate less conditioned place-preference to
cocaine than controls (Malanga et al., 2007a);
… are more likely to acquire cocaine self-administration
than controls (Rocha et al., 2002);
… self-administer more cocaine than controls (Rocha et
al., 2002);
… demonstrate more sensitization of dopamine release
in the nucleus accumbens after chronic cocaine
administration than gestational controls (Malanga et al.,
Saline
Cocaine
Saline
Cocaine 5 mg/kg Cocaine 20 mg/kg
submitted
) 5 mg/kg Cocaine 20 mg/kg
Post Test - Pre Test (sec/min)
20
5.
Saline
Cocaine 5
mg/kg
10
0
Cocaine 20
mg/kg
Conditioning Group
6.
-10
-20
-30
COC40
COC20
SPF40
SAL


20
10
0

-10

-20
-30
Saline
Cocaine 5
mg/kg
Drug Side - Saline Side (sec/min)
4.
30
Drug Side - Saline Side (sec/min)
30
20
COC40
COC20
SPF40
SAL



10
0
Cocaine 20
mg/kg
Conditioning Group
Conditioning Group
30
-10
-20
-30
Conditioning Group

Mice exposed to cocaine in utero
1.
2.
3.
4.
5.
6.
… habituate less to novelty/injection stress than nonexposed controls (Guerriero et al., 2005);
… demonstrate less locomotor sensitization to repeated
psychostimulant administration than gestational controls
(Crozatier et al., 2003; Guerriero et al., 2005);
… demonstrate less conditioned place-preference to
cocaine than controls (Malanga et al., 2007a);
… are more likely to acquire cocaine self-administration
than controls (Rocha et al., 2002);
… self-administer more cocaine than controls (Rocha et
al., 2002);
… demonstrate more sensitization of dopamine release
in the nucleus accumbens after chronic cocaine
administration than gestational controls (Malanga et al., In
Press)
Mice exposed to cocaine in utero
7.
8.
9.
10.
11.
… are more sensitive to the reward-potentiating effects of
cocaine on ICSS than controls (Malanga et al., 2007b);
…are more sensitive to the reward-potentiating effects of
selective dopaminergic agonists (Malanga et al., 2007b);
… demonstrate robust neuroanatomical, behavioral and
neurochemical changes that persist into adult life;
… provide a model for some of the clinical observations in
cocaine-exposed children, especially state or contextdependent differences; and
… demonstrate changes in dopamine release in the
nucleus accumbens that correlate directly with changes
seen in the effects of cocaine on operant or instrumental
behaviors and inversely with associational or Pavlovian
behaviors
Introduction
• Low sensitivity to subjective and motor effects of EtOH is associated
with increased EtOH abuse (Schuckit, et al.)
• High sensitivity to euphoric or hedonic effects (“liking” or “wanting”)
of EtOH is associated with increased EtOH abuse (de Wit, et al.)
– Positive hedonic effects are associated with psychomotor stimulation
during the rising phase of blood alcohol concentration (BAC)
– Higher doses and/or decreasing BAC are associated with sedation
and/or negative hedonic effects
• Animal studies
– “Do you feel it?” (drug-discrimination; self-administration)
– “Do you want more?” (self-administration; conditioned place-preference)
– “Do you like it?” (intracranial self-stimulation; self-administration)
MOTIVATION
REWARD
Expectancy
Consumption
ATTENTION
WITHDRAWAL
TIME
Intracranial
Self-Stimulation
Drug
Self-Administration
Introduction
Genetic contributions to alcohol sensitivity: inbred mouse strains
• C57Bl6/J
– Less motor stimulation/more sedation with
acute EtOH
– High levels of oral self-administration of EtOH
– Faster acquisition of IV self-administration of
EtOH
– Less behavioral sensitization to chronic EtOH
– Less conditioned place-preference to EtOH
– Normal EtOH withdrawal
• DBA/2
– High motor stimulation with acute EtOH
– No oral self-administration (without
sweetening) of EtOH
– Normal acquisition of IV self-administration of
EtOH
– More behavioral sensitization to chronic EtOH
– More conditioned place-preference to EtOH
– Enhanced EtOH withdrawal
How can we utilize these differences to separate the rewarding value of
alcohol – how much the animal LIKES and is rewarded by alcohol - from
its other behavioral effects in these mouse strains?
How can we separate the rewarding properties of alcohol – how
much the animal LIKES and is positively motivated to seek
alcohol – from its other behavioral effects in mice?
How can we measure changes in the rewarding value of alcohol –
if the animal LIKES alcohol more or less – after acute or chronic
alcohol exposure or consumption at different developmental
stages (fetal, adolescent, adult)?
What are the pharmacological mechanisms underlying the
motivational effects of alcohol in mice, and how do those
mechanisms change with exposure or consumption at different
developmental time points?
Intracranial Self-Stimulation (ICSS)
vs. Drug Self-Administration (IVSA)
• Psychological: Both methods utilize instrumental conditioning and measure operant
behavior; however, in IVSA the drug itself is the reinforcer, while in ICSS rewarding
intracranial electrical stimulation (brain stimulation-reward, or BSR) is the primary
reinforcer and drugs act by increasing or decreasing its rewarding value. In IVSA,
access to drug reinforces behavior during instrumental conditioning, while ICSS
measures the potentiating (or depreciating) effects of drugs on reinforcement of a
previously learned operant behavior.
• Neuroanatomical: IVSA measures effects of drugs on the entire nervous system, while
ICSS measures effects of drugs on rewarding electrical stimulation of a discrete set of
neural structures, the mesolimbic motor pathways or brain reward system
• Pharmacological: In contrast to IVSA, satiety does not develop for BSR and
pharmacological antagonism does not increase responding for BSR
• ICSS directly measures the positive or negative hedonic effects of drugs on
behavior. Because the animal works for BSR and drug delivery is
behaviorally non-contingent, ICSS does not measure how much the animal
“wants” the drug – ICSS measures how much the animal LIKES the drug.
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Ventral Tegmental Area
E
AT
M
TA
U
GL
Medial
Forebrain
Bundle
200
Rate of Response
(presses/minute)
0
32354045505663717989
112
126
141
158
100
Stimulus Frequency (Hz)
200
Max
½ Max
Rate of Response
(presses/minute)
Slope
0
32
Threshold
EF50q0
158
Stimulus Frequency (Hz)
200
Rate of Response
(presses/minute)
Δ
0
q0
32
158
Stimulus Frequency (Hz)
100
GENETIC MODEL
CHRONIC TREATMENT
DEVELOPMENTAL
EXPOSURE
% Change in
Reward
Threshold
0
0
0.1
1.0
10
Dose of Drug (mg/kg)
From: Kornetsky and Bain, NIDA Res Monogr 124, 1992
The release of dopamine in forebrain structures (nAc, PFC)
is necessary, but not sufficient, for BSR
• Dopamine and EtOH actions
– VTA dopaminergic neurons (Brodie and Appel 2000; Brodie 2002)
• No difference in in vitro basal firing rate, C57 vs. DBA
• EtOH stimulates cell firing in both C57 and DBA, but potency is higher in DBA
• Chronic EtOH (7 g/kg/d i.p. x 21d) does not change basal firing but does
increase EtOH potency to stimulate firing and decrease GABA potency to
inhibit firing in C57
– Dopamine release (Middaugh et al 2003; Zapata et al 2006)
• EtOH drinking (12% EtOH x 2 hr, 1.6 g/kg consumed, BAC~60 mg/dl)
stimulates DA release in the nAc of C57 mice
• No difference in basal extracellular DA levels or acute EtOH (2.0 g/kg i.p.)evoked DA release in nAc, C57 vs. DBA
• No difference in basal DA or EtOH-evoked DA release in nAc upon withdrawal
after chronic EtOH (vapor chamber 16 hr/d x 4d), C57 vs. DBA
The release of dopamine in forebrain structures (nAc, PFC)
is necessary, but not sufficient, for BSR
• Dopamine and EtOH (continued)
– Dopamine content, turnover and receptors (Ng et al 1994; George et al
1995)
• Bmax for D1 and D2 in striatum C57>DBA; Bmax for D2 in midbrain DBA>C57
• DA-stimulated adenylyl cyclase activity in striatum C57>DBA
• Total tissue DA in striatum and midbrain C57=DBA; DOPAC:DA in striatum
and midbrain C57<DBA, and increases in striatum of C57 mice after drinking
(10% EtOH 5hr/d x 5d; BAC~100 mg/dl)
– Dopamine receptors (McNamara et al 2006)
• Bmax for D1 in ventral striatum C57=DBA; Bmax for D3 in ventral striatum
DBA>C57
• D1 agonist (SKF 38393) potency to stimulate locomotion C57>DBA
• D3 agonist (PD 128907) potency to inhibit locomotion DBA>C57
R01 proposal to NIAAA
• Specific Aim 1
– To determine the effect(s) of alcohol on brain stimulationreward (BSR) in mice
– To investigate the pharmacological mechanisms mediating the
rewarding effects of alcohol in mice
• Specific Aim 2
– To determine if acute, intermittent administration changes the
rewarding effects of alcohol over time
– To determine if chronic alcohol exposure leading to physical
dependence changes the rewarding effect of alcohol,
particularly after withdrawal
• Specific Aim 3
– To determine if adaptations in dopaminergic mechanisms of
brain reward are involved in the effects of chronic alcohol
exposure and withdrawal on BSR
R01 proposal to NIAAA
• Specific Aim 1: Preliminary Data – Proof of Concept
– Responding for BSR in different inbred/outbred mouse strains
-7
Threshold (Coulombs 10 )
Responses/50s
5
100
Swiss
C57BL6/J
129S6Ev
DBA2/J
80
4
60
3
40
2
20
1
0
0
25
50
100 126
Stimulation
Frequency
(Hz)
Stimulation Frequency
(Hz)
C57
DBA
129 Swiss
Mouse
Strain
Strain
R01 proposal to NIAAA
• Specific Aim 1: Preliminary Data – Dose-Dependent Effects
– Acute effect of EtOH on BSR in C57 and DBA mice
– HYPOTHESIS: Acute administration of EtOH will potentiate the rewarding value of
BSR (i.e., will lower reward threshold, q0) in both C57 and DBA mice
q0 (% ofq Pre-Injection
(% of Baseline)Baseline)
175
Min 16-30
Min 0-15
*
150
125
*
Min 31-45
Min 46-60
*
*
100
0
75
50
25
*
*
**
*
*
DBA (n=7)
C57 (n=9)
*
*
*
*
* = P<0.05 vs. Vehicle
0
V 0.3 0.61.01.7
2.4
V 0.3 1.0 2.4 V 0.3 1.0 2.4
Alcohol
Dose(g/kg,
(g/kgp.o)
p.o.)
Alcohol Dose
V 0.3
1.0 2.4
R01 proposal to NIAAA
• Specific Aim 1: Preliminary Data - Pharmacokinetics
– Absorption, distribution and elimination of EtOH in C57 and DBA mice
Blood Alcohol
(mg/dl) (mg/dl)
Concentration
Blood Alcohol
Blood Alcohol Levels in DBA2/J and C57BL/6J Mice
after Gavage with 0.6 g/kg Alcohol
40
30
20
DBA (n=5, 90-Day Old)
C57 (n=5, 90-Day Old)
10
0
0
5
15
30
Minutes
After
Gavage
Minutes
after
Gavage
60
R01 proposal to NIAAA
• Specific Aim 1: Preliminary Data - Comparison of Cocaine Effects
– Acute effect of cocaine on BSR in C57 and DBA mice
– HYPOTHESIS: Acute cocaine administration will potentiate the rewarding value of
BSR (i.e., will lower reward threshold, q0) more in DBA than in C57 mice
**
150
175
**
100
Min 16-30
q0 (% ofq Pre-Injection
(% of Baseline)Baseline)
*
*
50
V
1 3 10 30 0
*
*
Min 46-60
*
*
* * ** *
**
*
*
DBA (n=4)
(n=7)
C57 (n=9)
V
Min 31-45
*
*
*
**
* *25
*
0
*
100
*
75
* *
Min 46-60
**
*
125
50
Min 16-30
150
**
Min 31-45
Min 0-15
0
q0 (% of Pre-Injection Baseline)
Min 0-15
C57 (n=9)
* *
DBA (n=4)
**
1 3 10 30
V
1 3 10 30
*
*
* *
* = P<0.05 vs. Vehicle
V
1 3 10 30
V 0.3
1.0 Dose
2.4 (mg/kg)
V 0.3
1.0 2.4 V 0.3
1.0 2.4
Cocaine
Alcohol
Dose(g/kg,
(g/kgp.o)
p.o.)
Alcohol Dose
V 0.3
1.0 2.4
R01 proposal to NIAAA
• Specific Aim 1: Preliminary Data – Voluntary Consumption
– Acute effect of self-administered EtOH on BSR in C57BL6/J mice
Consumption of 1.1
± 0.1(1.1
g/kg
EtOH
on Affects
first
Self-Administered
Alcohol
+ 0.1
g/kg)
minutes ofMin
ICSS
session
ICSS15
Responding:
0 -test
15 (n=6
C57 Mice)
Baseline)
Pre-DrinkingBaseline)
ofPre-Drinking
qq00 (%
(%of
120
*
100
80
60
40
20
*= P<0.05 vs. H2O
0
H2O
Alc 10%
Drinking
Solution
(1
Hr)
Drinking Solution (1 hour)
R01 proposal to NIAAA
• Specific Aim 2: Preliminary Data
– Effects of repeated, intermittent (every other day) administration of a rewardpotentiating dose of EtOH on BSR threshold
– HYPOTHESIS: Neither the reward-potentiating nor the reward-depreciating effects
of acute EtOH on BSR will change with repeated, intermittent administration
*
100
80
60
40
0
Baseline)
ofofPre-Injection
q0 (%
q (%
Pre-Injection Baseline)
Repeated Administration of Alcohol (0.6 g/kg, p.o):
Effects on ICSS in C57 Mice (n= 5-9)
20
*= P<0.05 vs. H2O
0
H2O
1
2
3
Replication
Replication
4
5
6
• 40
Specific Aim 2: Preliminary Data
– Consumption of modified Lieber-DeCarli liquid diet with EtOH (2.4 and 4.4 % v:v)
by C57BL6/J mice
35
30
25 40
20 35
Weight (g)
15
10
17
Control (n=5)
35
Alcohol (n=15)
30
30
25
25
20
20
15
15
0 10
10
5
16
40
5
5
2.4 % v:v
4.8 % v:v
0
0
-1
0
1
2
3
4
5
6
7
8
9
10
Day of Treatment
11
12
13
14
15
16
17
Volume Consumed (ml)
Volume Consumed (ml)
5
R01 proposal to NIAAA
EtOH consumed (g/kg)
Control (body wt)
Alcohol (body wt)
Control (vol)
Alcohol (vol)
R01 proposal to NIAAA
Research Design
• Specific Aim 1
– Experiment 1.1: Acute effect(s) of oral alcohol on BSR in
C57 and DBA mice
1.1a. Acute EtOH by oral gavage on BSR
1.1b. Pharmacokinetics of acute EtOH by oral gavage
– Experiment 1.2: Dopaminergic pharmacology of alcohol
reward in C57 and DBA mice
1.2a. Acute cocaine by i.p. injection on BSR
1.2b. Effect of SKF 82958 / SCH23390 on potentiation / depreciation of
BSR by acute EtOH
1.2c. Effects of quinpirole / eticlopride on potentiation / depreciation of
BSR by acute EtOH
R01 proposal to NIAAA
Research Design
• Specific Aim 2
– Experiment 2.1: Effect of acute, intermittent alcohol
administration on BSR in C57 and DBA mice
2.1a. Effect of repeated 0.6 g/kg EtOH p.o. (gavage) on BSR
2.1b. Effect of repeated 1.7 g/kg EtOH p.o. (gavage) on BSR
– Experiment 2.2: Effect of chronic alcohol exposure,
dependence and withdrawal on BSR in C57 and DBA mice
2.2a. Effect of acute EtOH withdrawal after chronic exposure on BSR
2.2b. Effect of repeated cycles of re-exposure to and withdrawal from
EtOH on BSR
2.2c. Effect of length of withdrawal from chronic EtOH on BSR
Experiment 2.2
Experiment 2.2a: Chronic alcohol exposure and withdrawal in C57 and DBA mice
BSR without EtOH
EtOH
0.6 OR 1.7 g/kg p.o.
+BAC
BAC
1 wk veh p.o. 4 wk EtOH 13% total calories (2.4% v/v EtOH)
6
12
24
48
Hours after withdrawal
Experiment 2.2b: Repeated cycles of chronic alcohol and withdrawal in C57 and DBA mice
EtOH
EtOH
0.6 OR 1.7 g/kg p.o.
0.6 OR 1.7 g/kg p.o.
BAC
+BAC
1 wk veh p.o. 4 wk EtOH 13% total calories (2.4% v/v EtOH)
(
1 wk withdrawal 24º EtOH 1 wk withdrawal
)x3
Experiment 2.2c: Variable duration of withdrawal from chronic alcohol in C57 and DBA mice
EtOH
EtOH
0.6 OR 1.7 g/kg p.o.
0.6 OR 1.7 g/kg p.o.
BAC
+BAC
1 wk veh p.o. 4 wk EtOH 13% total calories (2.4% v/v EtOH)
2 OR 4 wk withdrawal
24º EtOH
R01 proposal to NIAAA
Research Design
• Specific Aim 3
– Experiment 3.1: Dopaminergic mechanisms in the effects of
repeated cycles of chronic exposure to and withdrawal from
alcohol on BSR
3.1a. Effect of the D1 agonist SKF 82958 on BSR during and after chronic
EtOH and repeated cycles of withdrawal and re-exposure
3.1b. Effect of the D2 agonist quinpirole on BSR during and after chronic EtOH
and repeated cycles of withdrawal and re-exposure
– Experiment 3.2: Dopaminergic mechanisms in the effects of
chronic alcohol exposure and variable length of alcohol withdrawal
on BSR
3.2a. Effect of the D1 agonist SKF 82958 on BSR during and after chronic
EtOH and variable duration of alcohol withdrawal
3.2b. Effect of the D2 agonist quinpirole on BSR during and after chronic EtOH
and variable duration of alcohol withdrawal
Experiments 3.1 and 3.2
Experiment 3.1: Chronic alcohol exposure and repeated withdrawal in C57 and DBA mice
SKF 82958
1.0 mg/kg i.p.
OR Quinpirole
3.0 mg/kg i.p.
1 wk veh i.p.
SKF 82958
BAC
1.0 mg/kg i.p.
OR Quinpirole
3.0 mg/kg i.p.
(
1 wk withdrawal 24º EtOH 1 wk withdrawal
4 wk EtOH 20% of total calories
)x3
Experiment 3.2: Variable duration of withdrawal from chronic alcohol in C57 and DBA mice
SKF 82958
1.0 mg/kg i.p.
OR Quinpirole
1 wk veh i.p.
3.0 mg/kg i.p.
4 wk EtOH 20% of total calories
SKF 82958
BAC
1.0 mg/kg i.p.
2 OR 4 wk withdrawal
OR Quinpirole
3.0 mg/kg i.p.
24º EtOH
Future Directions
•
Effects of prenatal alcohol exposure on the development and adult
functioning of brain reward systems
•
Effects of adolescent alcohol exposure on the function of brain reward
systems in adult mice
•
Comparison of the effects of voluntary alcohol drinking to those of
forced alcohol consumption and non-contingent investigatoradministered alcohol on brain reward function
•
Investigation of the effects of pharmacological intervention on the
development of changes in the brain reward system after alcohol
exposure during vulnerable developmental stages
–
–
–
–
Opioid antagonists (e.g., naltrexone)
Calcium acetyl-homotaurinate (acamprosate)
Presynaptic glutamate release modulators (e.g., levitiracetam)
Atypical neuroleptics / non-selective partial D2 agonists (e.g., aripiprazole)
Future Directions
GABA
DA
D2-
GABAA
CTX
D1+
D2-
D1-
nAChR
D2-
GLU
nAChR
5HT1B-
D2-
DA
GLU GABA
AMPA
D2-
GABAB
VTA
mGluR1/5
GABAA nAChR
GABA
NMDA
m
nAc
D1+
D1/D2
MFB
mGluR1/5
AMPA
D2-
k
5HT3+
DA
D1/D2
NMDA
mAChR1
ACh