Role of ventral subiculum in context-induced reinstatement of heroin seeking in rats

Abstract

In rats, reexposure to heroin-paired contexts after extinction of lever responding in a different context reinstates heroin seeking. Previous reports indicate that ventral hippocampus/Ca1 region plays a critical role in cocaine-, cue- and context-induced reinstatement of cocaine seeking. Here, we examined whether ventral subiculum, the output region of ventral hippocampus, is involved in context-induced reinstatement of heroin seeking. We found that reversible inactivation of ventral subiculum, but not posterior Ca1, with the gamma-aminobutyric acid agonists muscimol + baclofen decreased context-induced reinstatement of heroin seeking. Our findings, together with previous studies on cocaine seeking, indicate a critical role of ventral subiculum in context-induced relapse across drug classes.

Keywords: Conditioned cues; drug environment; heroin self-administration; hippocampus; muscimol + baclofen; reinstatement; relapse.

Figure 1. Effect of bilateral injections of muscimol+baclofen into (A) ventral subiculum or (B) posterior Ca1 on context-induced reinstatement of heroin seeking

Left panels show Mean±SEM number of presses on the previously active lever after bilateral injections of muscimol+baclofen into ventral subiculum (n=8 per group) or posterior Ca1 (n=9 per group) prior to exposure to the Heroin context or the Extinction context. Right panels show approximate placements (mm from Bregma) of the injector tips for ventral subiculum or posterior Ca1 (Paxinos and Watson, 2005) and representative photomicrographs of cannula placements. * Different from the Vehicle condition, p<0.01.