Discriminative stimulus properties of benzodiazepines, barbiturates and pharmacologically related drugs; relation to some intrinsic and anticonvulsant effects.

Using a food-reinforced two-lever operant method, rats (n = 12) were trained to discriminate chlordiazepoxide (5 mg/kg, p.o.) from solvent (p.o.). With rats trained thus as subjects, generalization experiments were done with various benzodiazepines, barbiturates and related compounds, and with two neuroleptic drugs. The ability of these drugs to induce a discriminative stimulus complex similar to that induced by chlordiazepoxide, was then compared with some intrinsic and anticonvulsant effects of the same drugs. It was found that the discriminative stimulus properties of benzodiazepines, barbiturates, and related compounds correlate with the ability of these drugs to induce ataxia, as well as with part of their anticonvulsant activity. However, the stimulus properties of these drugs, as defined by the procedure described, are based neither on their ataxia-inducing effect, nor on their general depressant or sedative action. It is concluded that these properties constitute a pharmacologically highly specific phenomenon.