Carbamazepine effects on preoptic GABA release and pituitary luteinizing hormone secretion in rats

In vivo effects of carbamazepine (CBZ) on the neuroendocrine preopticopituitary feedback system were studied by local application of CBZ through a push-pull cannula into the preoptic area and measurement of local effects on gamma-aminobutyric acid (GABA) and distant effects on a subsequent biologic response: luteinizing hormone (LH). Perfusion with 8 and 12 micrograms CBZ/ml cerebrospinal fluid caused a reduction in preoptic GABA release and concomitant suppression of plasma LH levels. These results suggest a GABA component to the mechanism(s) of action of CBZ: (a) CBZ reduces extracellular available GABA concentration, and (b) owing to the known inhibitory role of preoptic GABA in pituitary LH secretion, an increase of postsynaptic GABAergic transmission by CBZ itself could be inferred.