Effect of time-out duration on the reinforcing strength of cocaine assessed under a progressive-ratio schedule in rhesus monkeys.

摘要: Progressive-ratio (PR) schedules of reinforcement have provided valuable information regarding the reinforcing strength cocaine and underlying neurobiological mechanisms. Parametric manipulations, such as altering time-out (TO) values, can affect shape dose-response curve. Previous studies used PR with widely varying parameters; thus complicating comparisons across experiments. The present study evaluated (0.005 – 0.9 mg/kg) a function post-reinforcement TO duration (5, 10, 30 or 60 min) under schedule in rhesus monkeys. Daily sessions ended when 2 h elapsed without an injection; total number injections was defined breakpoint (BP) value. When 10 min, relationship between dose received (i.e., BP) characterized by inverted U-shaped curve all Increasing to 30-min resulted rightward shift ascending limb curve, but did not self-administration higher doses. low further increased shortened 5 nor increasing min alter highest tested dose. These results suggest that drug accumulation plays role determining intermediate doses schedules. However, unaffected manipulating TO, suggesting BP value is useful measure strength.