Activation of Infralimbic cortex neurons projecting to the nucleus accumbens shell suppresses discriminative stimulus-triggered relapse to cocaine seeking in rats

Cocaine addiction is marked by high relapse rates, often triggered by drug-associated cues. These cues can be conditioned stimuli (CSs), which occur after drug intake and are paired with drug effects, and discriminative stimuli (DSs), which signal drug availability, regardless of ongoing drug-seeking behaviour. While projections from the infralimbic cortex (IL) to the nucleus accumbens (NAc) shell are known to regulate CS-induced cocaine relapse, their role in DS-triggered relapse is not known. To investigate this, we examined how activating IL[->]NAc shell projections influences relapse driven by DSs and CSs during abstinence from intermittent cocaine use. Female Sprague-Dawley rats received viral-mediated gene expression of excitatory designer receptors exclusively activated by designer drugs in the IL. Rats then self-administered cocaine during 12 intermittent-access sessions (5-min cocaine ON/25-min cocaine OFF, 4h/day). A discrete light (DS+) signalled drug-available periods, while a different light (DS-) signalled drug non-availability. During each DS+ period, cocaine infusions were paired with a compound light-tone (CS+). Four weeks later, rats were tested for cue-induced cocaine seeking following response-independent presentation of DS+, CS+ or both. Immediately prior to testing, rats received intra-NAc shell clozapine N-oxide or aCSF to activate IL terminals. DS+ alone and DS+/CS+ combined triggered greater cocaine seeking than did the CS+. Activation of IL[->]NAc shell projections suppressed relapse behaviour in DS+ and DS+/CS+ conditions. These findings highlight the distinct and powerful influence of DSs on relapse and identify the IL[->]NAc shell circuit as a promising target for relapse prevention.