PROGRESSIVE RATIO AND BEHAVIORAL ECONOMIC-EVALUATION OF THE REINFORCING EFFICACY OF ORALLY DELIVERED PHENCYCLIDINE AND ETHANOL IN MONKEYS -EFFECTS OF FEEDING CONDITIONS

The effect of feeding conditions on the reinforcing efficacy of orally -delivered drugs was evaluated using a progressive-ratio (PR) paradigm and a behavioral economic analysis of demand. Seven monkeys self-admi nistered phencyclidine (PCP) (0.06, 0.12, 0.25, 0.5, and 1.0 mg/ml) or ethanol (2, 4, 8, 16, and 32% wt/vol) and concurrent water from two d rinking spouts under concurrent PR schedules. The ratios increased fro m 8 to 4096, and 40 liquid deliveries were available after completion of each ratio schedule. The entire range of drug concentrations was pr esented in nonsystematic order under two feeding: conditions, food res triction and food satiation. Drug maintained responses, deliveries and break points were significantly greater than those maintained by wate r. Food restriction significantly increased the rate of PCP-maintained responses, deliveries and PR break points over the food satiation bas eline. There was also a significant interaction between feeding condit ion and drug concentration. Although ethanol-maintained responses, liq uid deliveries and break points consistently increased in five of seve n monkeys during food restriction, only drug concentration produced si gnificant differences in these measures. Using break point as a measur e of reinforcing efficacy, food restriction increased the reinforcing efficacy of PCP and had a more pronounced effect at higher drug unit p rices.