Effects of chemicals on delayed matching behavior in pigeons. II: tolerance to the effects of diazepam and cross tolerance to phencyclidine.

Pigeons were trained under a 2-sec matching to sample schedule. Diazepam, phencyclidine and pentobarbital all decreased matching accuracy. Chronic administration of diazepam after the session produced no effect on matching accuracy on the next day; however, two weeks of postsession diazepam administration produced tolerance to the effects of presession diazepam administration and cross tolerance to phencyclidine, but not to pentobarbital. After 6 weeks without chronic diazepam administration, both the tolerance to the effects of diazepam on matching accuracy and the cross tolerance to phencyclidine had disappeared.