Discriminative, disinhibitory, and depressant effects of several anticonvulsants

The discriminative attributes of drugs were used to assess the degree to which several anticonvulsants have behavioral effects resembling those of pentobarbital. Rats were trained to make alternative responses to obtain water, depending on whether they had been injected IP with pentobarbital (10 mg/kg) or saline 10 min before the session. The pentobarbital response was chosen in tests with phenobarbital, dimethylphenobarbital, or methsuximide in the anticonvulsant dosage range. Increasing doses increased the percentage pentobarbital choice. Response rate was generally increased by doses that increased percentage of pentobarbital choice. The rats predominantly chose the saline response when administered phenytoin, primidone, or phenylethylmalondiamide, even at doses that were sufficiently high to reduce the response rate. The results suggest that different types of depressant effects are associated with the anticonvulsants tested.