Effect of 6-hydroxydopamine lesions of the amygdala on intravenous cocaine self-administration under a progressive ratio schedule of reinforcement.
Bilateral six-hydroxydopamine (6-OHDA) lesions were placed in the amygdala of rats self-administering cocaine (1.5 mg/kg per injection i.v.) under a progressive ratio schedule of reinforcement. Post-lesion access to three doses of cocaine (1.5, 0.75 and 0.37 mg/kg per injection i.v.) revealed a lesion effect only at the highest dose. At this dose, the lesion caused a significant increase in breaking point. No change in the breaking point was produced at the lower two doses. The biochemical results show a significant reduction in dopamine and DOPAC levels within the amygdala and an increase in dopamine within the NACC. In contrast, noradrenaline and serotonin (5-HT) levels were unaffected by the lesion in any of the dissected areas. These results demonstrate that no specific effect on cocaine reinforcement was produced by 6-OHDA lesions of the amygdala. The possibility that the lesion may have attenuated the anxiogenic qualities of the high dose of cocaine is discussed.
McGregor
A
A
Life Sciences Research Centre, Carleton University, Ottawa, Canada.
Baker
G
G
Roberts
D C
DC
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D015116:5,7-Dihydroxytryptamine / Q000633:toxicity; D000679:Amygdala / Q000473:pathology / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001552:Benzazepines / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D002707:Chlordiazepoxide / Q000494:pharmacology; D003042:Cocaine / Q000008:administration & dosage*; D003891:Desipramine / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism*; D004971:Estrus; D005260:Female; D005473:Fluoxetine / Q000494:pharmacology; D007051:Ibotenic Acid / Q000633:toxicity; D007275:Injections, Intravenous; D008297:Male; D009928:Organ Specificity; D016627:Oxidopamine; D051381:Rats; D017208:Rats, Wistar; D012646:Self Administration; D013997:Time Factors; D014364:Tryptophan / Q000494:pharmacology
D001552:Benzazepines; D005473:Fluoxetine; D015102:3,4-Dihydroxyphenylacetic Acid; D007051:Ibotenic Acid; D015116:5,7-Dihydroxytryptamine; D002707:Chlordiazepoxide; D014364:Tryptophan; D016627:Oxidopamine; D003042:Cocaine; D003891:Desipramine; D004298:Dopamine