Discriminative stimulus properties of phenytoin in the pigeon.

Pigeons trained under a two-key drug discrimination procedure eventually learned to discriminate 5 mg/kg phenytoin from saline injections. When 1.25-20 mg/kg doses of phenytoin were substituted for the training dose, the percentage of responses directed to the phenytoin-appropriate key varied directly with dose. Chlorpromazine, d-amphetamine, diazepam, and phenobarbital failed to produce phenytoin-like patterns of responding.