An investigation on the role of nitric oxide in the modulation of the binding characteristics of various radioligands of GABA(A) receptors by 5α- pregnan-3α-ol-20-one in the rat brain regions

Chronic administration of N(ω)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, diminished the ability of 5α-pregnan- 3α-ol-20-one, a neurosteroid, to potentiate the [³H]muscimol (5 nM) binding in the rat hippocampus but not in the cerebellum or cerebral cortex. This effect of NAME was stereospecific and susceptible to reversal by the pre- treatment of rats with L-arginine. However, chronic administration of L-NAME did not affect the modulation of the [³H]flunitrazepam (2 nM) or [³⁵S]TBPS (4 nM) binding by the neurosteroid in any of the brain regions investigated in this study. These results suggest that nitric oxide may be involved in some of the effects of neurosteroids in hippocampus.