Self-administration of cocaine-pentobarbital mixtures by rhesus monkeys.
A number of experiments have evaluated self-administration of the combination of a stimulant and an opioid. Less is known about the combination of a stimulant and a CNS depressant. The present experiment was designed to examine self-administration of the mixture of cocaine and pentobarbital (PB). Rhesus monkeys (n=4) prepared with i.v. catheters were allowed to self-administer cocaine or saline under a progressive-ratio schedule. When responding was stable, doses of cocaine and PB, alone or in combination, were made available in test sessions. Cocaine functioned as a positive reinforcer in a dose-related manner in all monkeys. PB functioned as a relatively weaker reinforcer in one of four monkeys. Self-administration of intermediate doses of cocaine (0.025-0.1mg/kg per injection) was decreased when mixed with PB (0.05-0.2mg/kg per injection); full maximum responding was re-established when cocaine dose was increased. The magnitude of the shift to the right in the cocaine dose-response function was directly related to PB dose. When PB was given as an i.v. pretreatment there was no effect on cocaine self-administration up to a sedative dose of PB (5.6 mg/kg), suggesting that responding was not non-specifically suppressed by PB. Thus, simultaneous self-administration of PB diminished the potency but not the strength of cocaine as a reinforcer, potentially encouraging self-administration of larger doses of cocaine.
Woolverton
W L
WL
Division of Neurobiology and Behavior Research, Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500N. State Street, Jackson, MS 39216, USA. wwoolverton@psychiatry.umsmed.edu
Wang
Zhixia
Z
D000818:Animals; D016739:Behavior, Addictive / Q000139:chemically induced / Q000523:psychology; D003042:Cocaine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D008253:Macaca mulatta; D008297:Male; D010424:Pentobarbital / Q000008:administration & dosage*; D012055:Reinforcement Schedule; D012646:Self Administration
D004338:Drug Combinations; D010424:Pentobarbital; D003042:Cocaine