The effects of behavioral history on cocaine self-administration by rhesus monkeys.
The purpose of the present study was to examine whether a history of responding under schedules that generate either high or low response rates could modify previously established cocaine self-administration. Eight experimentally naive rhesus monkeys were trained to respond on one of two levers under a fixed-interval (FI) 5-min schedule of intravenous cocaine (0.03 mg/kg per injection) presentation. When responding was stable a cocaine dose-response curve (saline, 0.01-0.3 mg/kg per injection) was determined. Following completion of the dose-response curves, the monkeys were randomly assigned to one of two groups (n = 4/group) and trained to respond on the other lever under either a fixed-ratio (FR) 50 or inter-response times (IRT) > 30-s schedule of cocaine (0.03 mg/kg per injection) presentation. After 65 sessions responding was again maintained under the FI5-min schedule of 0.03 mg/kg per injection cocaine for 60 sessions, followed by redetermination of the cocaine dose-response curve. During the initial exposure to the FI schedule, the mean rate of responding was 4.02 (+/- 0.33) responses/min and the cocaine dose-response curve was characterized as an inverted-U shape function of dose, with peak responding at 0.03 mg/kg per injection. The FR50 schedule generated high rates (66.80 +/- 5.6 responses/min), while response rates under the IRT > 30-s schedule were low (2.62 +/- 0.2 responses/min). Following different behavioral histories, response rates under the FI5-min schedule were significantly higher for 60 sessions in FR-history monkeys compared to IRT-history subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Nader
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MA
Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1083.
Reboussin
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DM
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D008253:Macaca mulatta; D008297:Male; D012055:Reinforcement Schedule; D012646:Self Administration
D003042:Cocaine