Cocaine as a discriminative stimulus for responding maintained by food in squirrel monkeys.

Squirrel monkeys were trained in a choice procedure to discriminate a dose of 100 micrograms/kg cocaine from saline. Following an injection of cocaine, responding on the right lever was reinforced with food, whereas following an injection of saline, responding on the left lever was reinforced with food. A high degree of stimulus control (100% correct) was established within 20 experimental sessions. The dose-response function of cocaine on lever choice was then determined. When intermediate doses (10, 25 and 50 micrograms/kg) were administered prior to test sessions, a dose-dependent generalization decrement was seen. One monkey was found to discriminate as low as 25 microgram/kg cocaine from saline.