Yoon, J.H. & Branch, M.N. (2009).
Influences on cocaine tolerance assessed under a multiple conjunctive schedule of reinforcement.
Journal of the Experimental Analysis of Behavior, 92, 413-422.
Under multiple schedules of reinforcement, previous research has generally observed tolerance to the rate-decreasing effects of cocaine that has been
dependent on schedule-parameter size in the context of fixed-ratio (FR) schedules, but not under the context of fixed-interval (FI) schedules of
reinforcement. The current experiment examined the effects of cocaine on key-pecking responses of White Carneau pigeons maintained under a
three-component multiple conjunctive FI (10 s, 30 s, & 120 s) FR (5 response) schedule of food presentation. Dose-effect curves representing the
effects of presession cocaine on responding were assessed in the context of (1) acute administration of cocaine (2) chronic administration of cocaine
and (3) daily administration of saline. Chronic administration of cocaine generally resulted in tolerance to the response-rate decreasing effects of
cocaine, and that tolerance was generally independent of relative FI value, as measured by changes in ED50 values. Daily administration of saline
decreased ED50 values to those observed when cocaine was administered acutely. The results show that adding a fixed-ratio requirement to fixed-interval
schedules is not sufficient to produce schedule-parameter-specific tolerance. Tolerance to cocaine was generally independent of FI-parameter under the
present conjunctive schedules, indicating that a ratio requirement, per se, is not sufficient for tolerance to be dependent on FI parameter.
Key words: cocaine, tolerance, fixed-interval schedule, fixed-ratio schedule, conjunctive schedule, multiple schedule, key peck, pigeons