Previous results have shown that stimulation of the gamma-hydroxybutyrate (GHB) receptor modulates Ca2+ channel permeability in cell cultures. In order to confirm this result, we investigated the consequence of GHB receptor stimulation on nitric oxide synthase (NOS) activity in rat brain cortical punches rich in GHB receptors. The stimulation of these receptors by increasing amounts of GHB induced a progressive decrease in NOS activity. However, for GHB doses above 10 microM, this reduction was progressively lost, either after receptor desensitization or after stimulation of an additional class of GHB receptor having lower affinity. The effect of GHB was reproduced by the GHB receptor agonist NCS-356 and blocked by the GHB receptor antagonist NCS-382. The GHB-induced effect on Ca2+ movement was additive to those produced by veratrine, indicating that GHB modulates a specific Ca2+ conductance, which explains the modification in NOS activity and the increase in cyclic guanosine monophosphate levels previously reported.