Effects of diazepam, pentobarbital, phenytoin and pentylenetetrazol on hippocampal paired-pulse inhibition in vivo.

The effects of diazepam, pentobarbital, phenytoin and pentylenetetrazol on paired-pulse inhibition were assessed in the intact rat hippocampus. Diazepam (4 mg/kg i.p.) and pentobarbital (15 mg/kg i.p.) increased inhibition over control levels, while phenytoin (15 mg/kg i.p.) and pentylenetetrazol (20 mg/kg i.p.) decreased inhibition from control levels. The present results with diazepam, pentobarbital and pentylenetetrazol confirm previous reports. However, the present results indicate that augmentation of GABA-ergic inhibition is not involved in the anticonvulsant action of phenytoin.