Animal models of addictions Funding sources

IVO MASTER CLASS April 18-20, Den Haag, The Netherlands

Serge H. Ahmed | CNRS | Université Bordeaux 2

Beware: a French speaks English I learnt English by reading thousands of scientific papers. This explains my terrible pronunciation. It is not French chauvinism or seduction. I just don’t know where to put the stress on English words. Just to give you few hints about my handicap: Developed

Although The

Self-administration Do not hesitate to ask me to repeat! Serge H. Ahmed | CNRS | Université Bordeaux 2

Why do we use animal models? Quantitative spatiotemporal control over life’s triple helix Organism Genes

Ceteris paribus sic stantibus

Time

X

Environment Winslow & Duckwall 2001

Serge H. Ahmed | CNRS | Université Bordeaux 2

Obvious limitations of animal models ● No access to the mind of animals ~ Inferences from behavior

● Psychological homology is uncertain ~ Subjective aspects of addiction criteria

● Brain homology is uncertain ~ Rat versus human prefrontal cortex Human

Monkey

Rat

● Specific laboratory conditions ~ Limited extrapolation to humans

● No control over environment ~ Gene-environment correlations Types of G x E

Serge H. Ahmed | CNRS | Université Bordeaux 2

The initial animal condition Start with a drug-naïve animal

Give chance for drug self-exposure

Has this animal developed a behavior that looks like addiction? Serge H. Ahmed | CNRS | Université Bordeaux 2

The problem of the reference Basic experimental set-up

Prototypical outcome 35

AEY_19 Cocaine hits / h

30

ST

25 20 15 10 5

EXP

CTL

0 1

Response

4

7

10

13

16

19

22

Days Dose

Day 1 Day 24

Time 0

15

30

Time (min)

Serge H. Ahmed | CNRS | Université Bordeaux 2

45

60

Modeling cocaine addiction Experimental procedure

Cocaine intake escalation Accessibility 140

LgA

LgA rats ShA rats

ShA

Cocaine injections

120 100 80 60 40 20 0 1 2 3 4 5 6 7 8 9 10 11 12

Days

Response Pre

Dose

Post

Time Ahmed & Koob 1998 Science

Serge H. Ahmed | CNRS | Université Bordeaux 2

Generalization and correspondence Meta-analysis of the literature

% change from initial use

250 200

Possible parallels with DSM-IV criteria

ShA LgA

150 100 50 Nico

0 Coc

Stim

Opiates

-50 -100

Ahmed 2011 Animal models of drug addiction

Ahmed 2012 Neuroscience

Serge H. Ahmed | CNRS | Université Bordeaux 2

Search of molecular correlates Experimental strategy and design

Transcriptional remodeling

Naive Gene array (~ 1200)

ShA rats RNA

cRNA LH

LgA rats Scanning

Data analysis

Ahmed et al. 2005, PNAS

Serge H. Ahmed | CNRS | Université Bordeaux 2

Striatal microRNA regulates cocaine intake Taqman real-time PCR

Naive

ShA

LgA

Fluorescent in situ hybridization

Yoked

 miR-212

MeCP2

BDNF cocaine escalation

Note: there is no effect on limited access to cocaine

Hollander et al. 2010 Nature; Im et al. 2010 Nature Neurosci

Serge H. Ahmed | CNRS | Université Bordeaux 2

Choice, compulsion, disorder Cocaine, what else?

Standard experimental setting

- Sleeping? - Exploration? - Grooming? - Just waiting?

Drug or…drug ?

Definition of a mental disorder

0

30

60

90

120

150

180

Time (min)

“A negative psychological condition Is a psychiatric disorder if it is symptomatic of some underlying dysfunction within the  individual and is not merely an expectable response to a particular event or situation.”

Ahmed 2010 Neurosci Biobehav Rev

Serge H. Ahmed | CNRS | Université Bordeaux 2

A sweet choice Experimental set-up

Discrete-trials choice procedure Choice

Sampling C

C

S 2

1

S 4

3

C

C

C

C

C

C

C

C

S 5

S 6

S 7

S 8

S 9

S 10

S 11

S 12

Top view

Reward conditions Lever S

Lever C

Cocaine only

-

+

Saccharin only

+

-

Cocaine & Saccharin

+

+

Groups

Forward locomotion

Trials (per 10 min)

6 5 4 3 2 1

i.v. cocaine

Important features - Saccharin - No restriction - Closed economy - Limited trials - Choice intervals

0 1

4

7

10 13 16 19 22 25

Intervals (30s) Lenoir et al. 2007 PLoS ONE

Serge H. Ahmed | CNRS | Université Bordeaux 2

Time

Sweeter than cocaine

Sweet

1,0

0,5

Cocaine

0,0

-0,5

S+/C+ S+/CS-/C+

Acquisition (days)

Reinforcement strength 12 10 8 6 4 2 0

Latency (s)

Acquisition of preference

60 50 40 30 20 10 0

-1,0 0

3

6

9

12

15

S+/C- S-/C+ S+/C+

S+/C- S-/C+ S+/C+

Type of reward

Days

Lenoir et al. 2007 PLoS ONE

Serge H. Ahmed | CNRS | Université Bordeaux 2

Representative examples

Sweet

Cocaine During cocaine sampling

Top view

Sweet

Cocaine

Top view

Guillem et al., unpublished data

Top view

Serge H. Ahmed | CNRS | Université Bordeaux 2

Sweet preference is dose-independent Psychostimulant effect

Choice behavior 1,0

Sweet Lever S

150

0,5

0,0

100

Cocaine Lever C

Locomotion / 10min

200

50

-0,5

-1,0

0 0.25

0.75

1.5

Cocaine dose (mg)

0.25

0.75

1.5

Cocaine dose (mg)

Lenoir et al. 2007 | PLoS ON)

Serge H. Ahmed | CNRS | Université Bordeaux 2

Drug use severity and sweet choice Individual distribution

Prevalence of sweet preference

N = 184 Sweet choice > 50%

100

Median Mean

0,5

91% 0,0

-0,5

-1,0

9%

Frequency (%)

Cocaine Sweet Preference score

1,0

80 60 40 20 0 0

75 150 225 >226

Past cocaine use (mg) Cantin et al. 2010  PLoS ONE

Serge H. Ahmed | CNRS | Université Bordeaux 2

Sugar on my mind Cocaine- versus sugar-selective cells

Distribution in the n. accumbens

Cameron and Carelli 2012 Eur J Neurosci

Serge H. Ahmed | CNRS | Université Bordeaux 2

Sugar even better than dopamine Selective stimulation of VTA DA cells

Distribution in the n. accumbens

Domingos et al. 2011 Nature Neurosci

Serge H. Ahmed | CNRS | Université Bordeaux 2

Animal models of sugar addiction Repeated, intermittent access to sugared water Sugar

Sugar

Sugar

Sugar

Table 1. Evidence for addiction-like behavior

Dialysat

Substance Dependence (DSM-IV-TR)

Sugar Addiction-like Behavior in Rats

Escalation, tolerance

Escalation of sugar intake

Drug withdrawal

Physical and affective withdrawal

Consuming more than intended

Deprivation effect, escalation

Continued use despite problems

Resistance to punishment

Table 2. Evidence for addiction-like neural changes Signaling pathways

Direction of change

D1 receptor binding

Increased

D2 receptor binding

Decreased

D3 recptor mRNA

Increased

Preproenkephalin mRNA

Decreased

DA/ACh balance

Altered during withdrawal

Ahmed et al. 2012 Neuroscience in the 21st Century

Serge H. Ahmed | CNRS | Université Bordeaux 2

A difficult choice to make? ? ● Most rats are resilient to drug addiction, only few are vulnerable

● Rats do develop drug addiction but can be hooked even more to sugar

● Rats do develop drug addiction but can be “treated” with nondrug alternatives

● Addiction, behavioral or else, is a voluntary choice not a brain disease

Buridan’s ass

Serge H. Ahmed | CNRS | Université Bordeaux 2

Acknowledgements

Drug escalation studies

Drug choice studies

George Koob John Walker Daniel Lin Paul Kenny Osnat Ben-Shahar Loren Parsons Athina Markou

Magalie Lenoir Fushia Serre Lauriane Cantin Dubreucq Sarah Nathalie Vanhille Eric Augier Caroline Vouillac Claudia Mihindou Youna Vandaele Karine Guillem

Robert Lutjens Pietro Sanna Martine Cador Magalie Lenoir Claudia Mihindou Karine Guillem

Serge H. Ahmed | CNRS | Université Bordeaux 2

Food addiction Preliminary clinical evidence Table 1. Addiction diagnostic adapted to food

Preliminary neurobiological evidence Striatal D2 receptors

Controls

Obese people

Table 2. Percentage of food addiction diagnosis

(Wang et al. 2001 | Lancet; Volkow et al. 2008 | Neuroimage)

Serge H. Ahmed | CNRS | Université Bordeaux 2

Effect of extended cocaine use Choice behavior

Effects of extended cocaine use 1,0

Lever S Sweet

6 h / day

0,5

0,0 Time

Lever C Cocaine

Pattern

-0,5

Observed effects

Authors / Date / Journal

Drug intake escalation

Ahmed & Koob / 1998 / Science

Increased reinstatement

Ahmed & Cador / 2006 / NPP

Increased motivation

Wee et al. / 2007 / NPP

Resistance to punishment

Vanderschuren / 2004 / Science

Decreased reward function

Ahmed et al. / 2002 / Nat Neurosci

0,5

Decreased DA signaling

Nader et al. / 2006 / Nat Neurosci

0,0

LHA synaptic remodeling

Ahmed et al. / 2005 / PNAS

Increased dendritic spines

Ferrario et al. / 2005 / Biol Psychiatr

OFC functional changes Increased striatal miRNA

George et al. / 2008 / NPP Hollender et al. / 2010 / Nature

(Ahmed 2011 | Ahmed & Kenny | 2011)

Days

-1,0 1,0

1

2

3

4

5

6

7

8

9 10

-0,5

Doses

-1,0 0.25

0.75

1.5

(Lenoir et al. 2007 | PLoS ONE)

Serge H. Ahmed | CNRS | Université Bordeaux 2

Quantifying the relative value of sweetness Preference shift

0.2% 0.04% 0.008% 0.0016%

0,5

0,0

-0,5

10 9 8

Indifferent point

Preference score Cocaine Sweet

1,0

Subjective equality

7 6 5 4 3 2 1

-1,0 0

2

4

6

8

10

12

14

16

0 0,001

Relative cost of saccharin

0,010

0,100

1,000

Saccharin concentration (%)

Cantin et al. 2010 PLoS ONE

Serge H. Ahmed | CNRS | Université Bordeaux 2

Sugar, sweetness and calories Hungry rats prefer sucrose

Choice behavior Sacc 0.2% Sucr 10%

1,0

Cocaine Sweet Preference score

Indifferent point

16

12

8

4

0

0,5

0,0

-0,5

-1,0 5

10

15

20

0

2

4

6

8

10

12

Relative cost

Sucrose (%) Cantin et al. 2010 PLoS ONE

Serge H. Ahmed | CNRS | Université Bordeaux 2

14

16

Effect of sweetness experience

250

w1

Sweet Water

Volume / rat (ml)

200 w2 150

w3

w4

100 50 0

Choice behavior

1,0

Preference score Cocaine Sweet

Ad libitum access in home cage

0,5

0,0

-0,5 HAB (n = 11) CTL (n = 73) -1,0

1

4

7

10 13 16 19 22 25

1

2

Days

3

Days (Augier, Mihindou et al. 2011 | in preparation)

Serge H. Ahmed | CNRS | Université Bordeaux 2

4

5

Effect of the anxiolytic diazepam Expression of sweet preference

*

100

% time in drug side

Sweet

1,0

0,5

0,0

Cocaine

Preference score

Time spent in drug side

-0,5

-1,0

75

50

25

*

0 0

2

4

8

16

0

2

Diazepam (mg/kg)

4

8

Diazepam (mg/kg)

(Augier, Vouilac & Ahmed 2012 | Addiction Biology)

Serge H. Ahmed | CNRS | Université Bordeaux 2

16

Effect of self-paced choice Work for choice

Main outcomes (n = 23) AQP1_6

AQP1_6

1 0 -1

X10

1 0 -1 0

30

60

90

120

150

180

0

AQP2_10

1 0 -1 0

X2

30

60

90

120

150

180

90

120

150

180

0

30

60

90

120

150

180

60

90

120

150

180

AQP2_9

1 0 -1

1 0 -1 0

30

60

90

120

150

180

Time (30-min bins)

X2

60

1 0 -1 AQP2_9

Choice trial

30

AQP2_10

0

30

Time (30-min bins)

Sweet water

(Augier, Vouillac & Ahmed 2012 | submitted)

Serge H. Ahmed | CNRS | Université Bordeaux 2

Cocaine

Assessment of brain reward function Brain self-stimulation

Method of limits

Experimental procedure -1 h

Access Accès

-1 h

Access Accès

… Time

Ahmed et al. 2002 Nature Neurosci

Serge H. Ahmed | CNRS | Université Bordeaux 2

Decreased reward thresholds Decrease in reward processing

Reward-escalation correlation

150

6 5

130

Intake escalation

Reward threshold (%)

140

120 110 100 90

LgA rats ShA rats

80 0

4 3 2 Intake

Deficit

1 0

1 2 3 4 5 6 7 8 9 10 11 12

0

Days

1

2

3

4

Reward deficit Ahmed et al. 2002 | Nature Neurosci

Serge H. Ahmed | CNRS | Université Bordeaux 2

5

6

Cocaine PD and PK Dialysat

Striatal cocaine

Striatal dopamine

LgA ShA Dopamine (%)

Cocaïne (nM)

450

300

150

400

400

300

300

Locomotion

600

Stimulant effect

200

100

200

100

0

0

0

0.0 0.12 0.25 0.5 1.0

0.0 0.12 0.25 0.5 1.0

0.0 0.12 0.25 0.5 1.0

Dose, iv (mg)

Dose, iv (mg)

Dose, iv (mg)

Ahmed et al. 2003 J Neurochem; Ahmed & Cador 2006 NPP

Serge H. Ahmed | CNRS | Université Bordeaux 2

Resistance to punishment

Cocaine intake

1h 1h

1h

Bas

Day 1

% suppression

Injections / 1st h

20

10

0 ShA

LgA

1h

Day 2

Uncond. suppression

40

30

1h

Day 3

Cond. suppression

140

140

LgA rats

120

120

ShA rats

100

100

80

80

60

60

40

40

20

20

0

0 ShA

LgA

Bas

Ahmed 2012 Neuroscience

Serge H. Ahmed | CNRS | Université Bordeaux 2

1

2

3