Amphetamine affects the extinction of self-stimulation differently in prefrontal cortex and posterior hypothalamus of rats.
The effects of amphetamine on the extinction of intracranial self-stimulation (ICSS) and on postextinction ICSS performance were examined in rats implanted with electrodes either in medial prefrontal cortex (mPFC) or in the posterior hypothalamus-ventral tegmental area (PH-VTA). Lever-pressing for ICSS was allowed to stabilize in daily 15-minute sessions before each animal was exposed to 5 minutes of extinction (responding without reward). Animals were administered either 0.25 mg/kg d-amphetamine or saline before baseline, extinction and postextinction sessions. After amphetamine treatment, the number of lever presses during extinction was higher in mPFC animals and lower in PH-VTA animals compared with saline-treated controls. Rates did not change immediately after extinction but, one day later, rates had increased in all saline-treated animals (both PH-VTA and mPFC animals) and had decreased in all amphetamine-treated animals. These findings demonstrated that the effects of amphetamine on the extinction of ICSS were different in cortical and hypothalamic sites, possibly because of regional differences in stimulus-evoked reinforcement and inhibitory processes.
West
C H
CH
Department of Psychiatry, Emory University School of Medicine, Georgia Mental Health Institute, Atlanta 30306.
Michael
R P
RP
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects*; D003913:Dextroamphetamine / Q000494:pharmacology*; D005108:Extinction, Psychological / Q000187:drug effects*; D007031:Hypothalamus / Q000187:drug effects*; D007034:Hypothalamus, Posterior / Q000187:drug effects*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012653:Self Stimulation / Q000187:drug effects*; D013997:Time Factors
D003913:Dextroamphetamine