In vivo effects of phenytoin and phenobarbital on GABA receptors in rat cerebral cortex and cerebellum

The in vivo effects of anticonvulsants on specific binding of 3H]GABA in the rat brain were examined in male Wistar rats. Acute treatment with phenobarbital increased specific 3H]GABA binding in the cerebral cortex, whereas repeated treatment with phenobarbital failed to change 3H]GABA binding. 3H]GABA binding in the cerebellum was not influenced by phenobarbital administration. Acute treatment with phenytoin produced no change in 3H]GABA binding, whereas repeated treatment with phenytoin caused a significant increase in 3H]GABA binding in the cerebellum, but not in the cerebral cortex. The effects of these anticonvulsants may be due, at least in part, to GABA receptor-mediated mechanisms.