The effects of excitotoxic lesions of the nucleus accumbens core or shell regions on intravenous heroin self-administration in rats.
BACKGROUND
It has been suggested that the nucleus accumbens (NAcc) may be involved in heroin reward, and the core and shell regions respond differently following administration of a number of drugs of abuse.


OBJECTIVE
The possible role of the NAcc core and shell subregions in the acquisition of heroin self-administration behaviour was investigated.


METHODS
Rats were given selective excitotoxic lesions of either the nucleus accumbens core or shell before the acquisition of responding for i.v. heroin (0.04 mg/infusion) under a continuous reinforcement schedule in daily 3 h sessions. After sham-lesioned rats reached a stable baseline, a between-sessions heroin dose-response 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. The NAcc core lesion group showed reduced levels of responding during the acquisition of heroin self-administration and a reduction in responding during the heroin dose-response function, although this behaviour was sensitive to changes in the dose of heroin.


CONCLUSIONS
The NAcc shell does not appear to be critical for heroin self-administration, whereas the NAcc core, although apparently not essential in mediating the rewarding effect of i.v. heroin, may mediate processes that are of special importance during the acquisition of instrumental behaviour.
Department of Experimental Psychology, University of Cambridge, UK.
H L
HL
Alderson
J A
JA
Parkinson
T W
TW
Robbins
B J
BJ
Everitt
D000818:Animals; D003216:Conditioning, Operant; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D006556:Heroin Dependence / Q000523:psychology*; D007051:Ibotenic Acid / Q000633:toxicity; D008297:Male; D020258:Neurotoxicity Syndromes / Q000473:pathology / Q000523:psychology*; D009498:Neurotoxins / Q000633:toxicity; D009714:Nucleus Accumbens / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D017378:Quinolinic Acid / Q000633:toxicity; D051381:Rats; D012055:Reinforcement Schedule; D012646:Self Administration; D015819:Substance Abuse, Intravenous / Q000523:psychology*
D018690:Excitatory Amino Acid Agonists; D009498:Neurotoxins; D007051:Ibotenic Acid; D017378:Quinolinic Acid