Nitric oxide induces neurotransmitter release from hippocampal slices

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