The effects of excitotoxic lesions of the nucleus accumbens core or shell regions on intravenous heroin self-administration in rats

Rationale: It has been suggested that the nucleus accumbens (NAcc) may be i nvolved in heroin reward, and the core and shell regions respond differentl y following administration of a number of drugs of abuse. Objective: The po ssible role of the NAcc core and shell subregions in the acquisition of her oin self-administration behaviour was investigated. Methods: Rats were give n selective excitotoxic lesions of either the nucleus accumbens core or she ll before the acquisition of responding for IV heroin (0.04 mg/infusion) un der a continuous reinforcement schedule in daily 3 h sessions. After sham-l esioned rats reached a stable baseline, a between-sessions heroin dose-resp onse function was established. Results: Rats with lesions of the NAcc shell did not differ significantly from sham controls in either the acquisition of heroin self-administration or in their heroin dose-response function. Th e NAcc core lesion group showed reduced levels of responding during the acq uisition of heroin self-administration and a reduction in responding during the heroin dose-response function, although this behaviour was sensitive t o changes in the dose of heroin. Conclusions: The NAcc shell does not appea r to be critical for heroin self-administration, whereas the NAcc core, alt hough apparently not essential in mediating the rewarding effect of IV hero in, may mediate processes that are of special importance during the acquisi tion of instrumental behaviour.