Effects of cocaine administration and withdrawal on the performance of pigeons under a fixed-consecutive-number schedule with and without an external discriminative stimulus.

The effects of administering and withdrawing cocaine (0.3, 1, 3, and 10 mg/kg) were evaluated in pigeons responding under a fixed-consecutive-number schedule of food presentation with (FCN-S(D)) and without (FCN) an external discriminative stimulus. Under both schedules, acute administrations of 10 mg/kg reduced accuracy (per cent reinforced runs) and lower doses had no systematic effect. Both 3 and 10 mg/kg doses reduced response rates under the FCN schedule, but only the 10 mg/kg dose did so under the FCN-S(D) schedule. With chronic exposure to increasing doses (0.3, 1, 3, and 10 mg/kg), tolerance developed to the rate- and accuracy-decreasing effects of 10 mg/kg under both schedules. Abrupt withdrawal from chronic cocaine (10.0 mg/kg) did not disrupt performance under either schedule. This indicates that behavioral dependence did not occur in the present study.