Self-administration of orally-delivered methohexital in rhesus monkeys with phencyclidine or pentobarbital histories: effects of food deprivation and satiation.
Orally-delivered methohexital was demonstrated to function as a reinforcer for rhesus monkeys with either phencyclidine or pentobarbital self-administration histories. The effects of food deprivation and food satiation were compared across a wide range of methohexital concentrations. Initially, three monkeys were trained to orally self-administer phencyclidine (0.25 mg/ml) and water, and three were trained to orally self-administer pentobarbital (0.5 mg/ml) and water under concurrent fixed-ratio (FR) schedules during daily 3-hr sessions. Liquid deliveries during the session (drug and water) and intersession (water) were contingent upon lip contact responses on solenoid-operated drinking spouts. The monkeys were first tested while food deprived by maintaining them at 85% of their free-feeding body weights. Methohexital concentrations were presented in the following order, and each concentration was held constant until at least five or six sessions of stable behavior were obtained: 2, 2.8, 4, 2 (retest), 1, 0.5, (plus 0.25 and 0.125 in monkey M-W) and 2 (retest) mg/ml. The monkeys were then food satiated by allowing them unlimited access to food, and the methohexital concentration series was repeated. During food deprivation, the concentration-response functions generally resembled an inverted U. Concurrent water-maintained responding was generally low, but it increased in some monkeys as methohexital concentrations increased in some monkeys. During food satiation, methohexital-maintained responding was not different from water-maintained responding in some monkeys, but in others it was substantially higher than water-maintained responding. Maximum drug intake ranged from 20.4 to 93.8 mg/kg during food deprivation and from 6.4 to 64.2 during food satiation among the six monkeys.(ABSTRACT TRUNCATED AT 250 WORDS)
D000284:Administration, Oral; D000818:Animals; D005508:Food Deprivation / Q000187:drug effects*; D008253:Macaca mulatta; D008297:Male; D008723:Methohexital / Q000008:administration & dosage* / Q000494:pharmacology; D010424:Pentobarbital / Q000494:pharmacology*; D010622:Phencyclidine / Q000494:pharmacology*; D012054:Reinforcement, Psychology; D012527:Satiation / Q000187:drug effects*; D012646:Self Administration; D013997:Time Factors
D008723:Methohexital; D010424:Pentobarbital; D010622:Phencyclidine