Discriminative stimulus effects of H(1)-anti-histamines in cocaine-trained pigeons.
Pigeons (n = 4) were trained to discriminate cocaine (3.0mg/kg, i.m.) from saline in a two-key, food-reinforced drug discrimination paradigm. After acquisition of the discrimination, the H(1)-antihistamines, chlorpheniramine, tripelennamine, diphenhydramine, promethazine and hydroxyzine, were administered before test sessions to determine if these antihistamines shared discriminative stimulus (DS) effects with cocaine. Chlorpheniramine (0.3-5.6mg/kg) and tripelennamine (0.1-1.7mg/kg) substituted, (i.e. > 80% cocaine-key responding) in all four birds. Diphenhydramine (0.1-10mg/kg) and promethazine (0.1-56mg/kg) substituted for cocaine in three and two birds, respectively, while hydroxyzine (1.0-100mg/kg) did not substitute for the training drug in any bird. These results, in conjunction with results from a previous study in which several antihistamines shared DS effects with d-amphetamine, suggest that the DS effects of some H(1)-antihistamines may be similar to those of psychomotor stimulants.
Drug Abuse Research Center, Department of Psychiatry, The Pritzker School of Medicine, The University of Chicago, 5841 S. Maryland Avenue, Chicago, Illinois 60637 USA.
J.P.
JP
Zacny