NITRIC-OXIDE INDUCES NEUROTRANSMITTER RELEASE FROM HIPPOCAMPAL SLICES

Hydroxylamine (1-300 muM), a nitric oxide generator, stimulated the release of [H-3]norepinephrine ([H-3]NE) and [C-14]acetylcholine ([C-14]ACh) from rat hippocampal slices in a concentration-dependent manner (EC50 almost-equal-to 30 muM). A maximally effective concentration of hydroxylamine (300 muM) produced a 24-fold increase in the basal [H-3]NE and 3.6-fold increase in the in the basal [C-14]ACh efflux. Sodium nitroprusside (SNP), also stimulated the release of [H-3]NE, but only at high concentrations (10-30 mM). Calcium-free experimental buffer (1 mM EGTA) abolished the response. Hemoglobin (0.3 muM) inhibited the effect of 100 muM hydroxylamine in a manner which was specific for nitric oxide. In addition, 100 muM hydroxylamine increased the efflux of endogenous GABA and glutamate by 3- and 6-fold, respectively.