Feeding conditions alter the demand for phencyclidine and ethanol: A behavioral analysis.

This experiment examined the effects of feeding conditions on orally self-administered phencyclidine (PCP) or ethanol in rhesus monkeys using a behavioral≡oral economic analysis. Drug intake was measured as a function of drug cost, which was varied by changes in the fixed ratio (FR) schedule. The monkeys were trained to respond for PCP (0.25 mg/ml) or ethanol (8% wt/vol) with concurrent water available under FR 4-128 schedules. As the FR increased. drug intake decreased in a positively decelerating manner. Results suggest that food deprivation increased the reinforcement value of the drugs as well as significantly increasing consumption of both PCP and ethanol. In addition, ethanol and PCP deliveries showed proportionally greater increases due to food deprivation as FR increased. Together, these results suggest that food deprivation increases the reinforcing efficacy of drugs and this eifect is enhanced as the cost (FR) of the drug increases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Combined effects of buprenorphine and an alternative nondrug reinforcer on phencyclidine self-administration in rhesus monkeys.

Six rhesus monkeys self-administered orally delivered phencyclidine (PCP; 0.35 mg/ml) with saccharin (0.3 or 0.03 % wt/vol) or water under concurrenl fixed-ralio (FR) schedules. During daily 3-hr sessions, subjects had concurrent access to liquids: PCP versus water, PCP versus saccharin. or saccharin versus water. The FR of both liquids was varied (4, 8, 16, 32, and 64) in nonsystematic order and when behavior was stable at each FR, buprenorphine (0.005 mg/kg) was injected intramuscularly for 5 days. Buprenorphine treatment decreased PCP deliveries by 16–65% across the range of FR values when compared with the no-treatment baseline, and concurrent saccharin reduced PCP deliveries from 34 to 63%. Combining buprenorphine treatment and concurrent availability of saccharin produced decreases in PCP deliveries of 70–87% from the no-trealmenl baseline across the FR values. Greater reductions were found at the highest FR values. Pmax values were shifted to the left under all treatment conditions, suggesting that the reinforcing efficacy of the drug was reduced. These findings suggest that pharmacological and behavioral treatments produce additive reductions in drug self-administration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-administration of cocaine, alfentanil, and nalbuphine under progressive-ratio schedules: Consumer demand and labor supply analyses of relative reinforcing effectiveness.

Progressive-ratio (PR) schedules of intravenous (IV) drug self-administration are useful for establishing the relationships between reinforcing effectiveness and pharmacological actions of abused drugs. The authors compared the reinforcing effects of the high-efficacy opioid alfentanil, the low-efficacy opioid nalbuphine, and cocaine using a PR schedule of IV drug injection in rhesus monkeys in which the response requirement increased during the experimental session and the initial response requirement (IRR) was varied. Analyses based on either consumer demand or labor supply models of behavioral economics revealed that the relative reinforcing effectiveness of cocaine and alfentanil was greater than that of nalbuphine. These results suggest that PR schedules with varying IRRs can provide meaningful estimates of the relative reinforcing effectiveness of abused drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)