Discriminative stimulus properties of local anesthetics in d-amphetamine- and pentobarbital-trained pigeons

Pigeons were trained to discriminate either d-amphetamine (1.7 mg/kg, IM) or pentobarbital (10 mg/kg, IM) from saline in a two-key, food-reinforced drug discrimination paradigm. Cocaine, procaine, and lidocaine were administered before test sessions to determine if these local anesthetics shared discriminative stimulus (DS) properties with either training drug. Cocaine (0.1-3.0 mg/kg) substituted for d-amphetamine in all 4 birds from the d-amphetamine-trained group. Procaine (3.0-56 mg/kg) substituted in 3 of the 4 birds from this group, and lidocaine (3.0-30 mg/kg) did not substitute in any bird. In contrast, cocaine, procaine, and lidocaine did not substitute for pentobarbital in any bird in the pentobarbital-trained group. These results suggest that the DS properties of some local anesthetics may be similar to those of psychomotor stimulants. Further, although some local anesthetics may have sedative-like actions, apparently these are not the basis of their DS effects.