GABA receptor alterations after chronic lithium administration. Comparison with carbamazepine and sodium valproate.

1. Effects of lithium, carbamazepine, sodium valproate and baclofen on GABA receptors were examined in several regions of the rat brain. 2. [3H]Muscimol (MUS) and [3H] (-)baclofen (BAC) were used to label GABAA and GABAB receptors, respectively, in synaptic membranes from rat brain. 3. Single treatment with lithium chloride, carbamazepine or sodium valproate did not change [3H]MUS or [3H]BAC binding in the frontal cortex, hippocampus and thalamus. 4. Following chronic treatment with lithium, carbamazepine or sodium valproate, [3H]BAC binding was significantly increased in the hippocampus but not in the frontal cortex, thalamus or striatum. 5. [3H]Muscimol binding did not change in any region examined after chronic treatment with lithium, carbamazepine or sodium valproate. 6. Single and chronic administration of baclofen did not change [3H]MUS or [3H]BAC binding. 7. One common mechanism of action of mood stabilizers may be mediated by GABAB receptors in the hippocampus.