Neurocircuitry of Relapse

Circuitry Mediating Motivated Behavior VTA dopamine Basal Ganglia Anterior Cingulate Ventral Orbital Amygdala Hippocampus Opioids Ethanol THC Nicotine Opioids Cocaine Amphetamines Drug Reward Glutamate

PET/fMRI of Cocaine Craving Childress et al., 1999; Am.J.Psychiat

Self-administration of Cocaine

Rats Taking Cocaine

Dopamine GABA Glutamate GABA Peptides MOTOR MEMORY Prefrontal Cortex Nuc Accum Drug Seeking COKE LIMBIC PRIME Amygdala Basolateral Dopamine Cells Dopamine Cells Extended Amygdala CRF; Norepinephrine STRESS CUE McFarland and Kalivas, JNeurosci, 2001; McFarland et al., JNeurosci, 2003, 2004

Role of Cortical Glutamate in Regulating Drug-Seeking Behavior Drug Seeking dPFC NA core Record Glutamate Here Inhibit Here Krista McFarland

Inhibition of the Dorsal PFC Blocks Cocaine-induced Glutamate Release in the Accumbens and Reinstatement McFarland et al., J. Neuroscience, Time (min) * * * * * * Cocaine Saline Bac/Mus Active Lever Presses Glutamate (% change) 100

Conclusion The circuit mediating reinstatement of drug-seeking includes the glutamatergic projection from the prefrontal cortex to the nucleus accumbens. Hypothesis Changes in protein function in the projection from the prefrontal cortex to the nucleus accumbens are targets for developing drugs to treat addiction

Leap Between Behavior and Proteins Change in Gene Expression 3 Weeks

pfc N. Acc Cortico-accumbens Pathology Dysregulated Glutamatergic Response to Motivational Stimuli xCT AGS3

N C AGS3 Structure/ Function And Steve Lanier, LSU Med Ctr, New Orleans Bowers et al., Neuron (2004) Scott Bowers

AGS3 and Receptor - G Protein Coupling Transmitter G  Gi  GDP Second Messenger AGS3 Metabotropic Receptor C SS S CC Accumbens core AGS Repeated Saline Repeated Cocaine * Withdrawal from Cocaine Increases AGS3 in PFC and NAcore GTP

Reversing Cocaine-induced Rise in AGS-3 in the PFC Prevents Reinstatement Active Lever Presses 8 8 Pump in Pump Out Self-admin Extinction Reinstate Extinction * No effect on food reinstatement; 2nd antisense oligo also works AS Rn 2 weeks

Conclusions  Cocaine withdrawal increases AGS3 and decreases Gi signaling in the PFC.  Increased AGS3 partly underlies cocaine- primed reinstatement. Hypothesis AGS3 contributes to the dysregulation of prefrontal cortex in addiction.

Basal Extracellular Glutamate is Reduced in the Accumbens after Withdrawal From Cocaine Pierce et al., J. Neuroscience, [Glu]i - [Glu]o [Glu]i Cocaine (2.5 µM) Saline (5.7 µM)

What Regulates Extracellular Glutamate Levels? Baker et al., J. Neuroscience, 2002 Dave Baker

N-acetylcysteine Blocks Reinstatement-induced Rise in Glutamate SalineNAC Test Extinction * Active Lever Presses Glutamate (pmol/sample) Time (min) Cocaine NAC or Saline Baker et al., Nature Neuroscience, 2003  Effect of N-acetylcysteine is dose-related  N-acetylcysteine does not alter food reinstatement or cocaine self-administration

mGluR2/3 PKA Glu Cys Glu Cys/Glu exchanger N-acetylcysteine (NAC): NAC GSH Cys 1)Increases Cys/Glu exchange 3) Stimulates mGluR2/3 autoreceptors 4) Inhibits synaptic glutamate release 2) Restores extracellular glutamate

pfc N. Acc Relapse Cortico-accumbens Pathology Drug Associated Stimulus Relapse to Drug-Seeking N. Acc pfc Reduced PFC Function Increased AGS3 (Bowers et al, Neuron, 2004) Altered Accumbens Function Reduced xCT (Baker et al., NatNeuro, 2003) Reduced Homer (Swanson et al., JNeurosci, 2001;Szumlinski et al., Neuron, 2004) Decreased Glutamate (Pierce et al., JNeurosci, 1996))