Noradrenaline release from rat hippocampus

Nitrogen monoxide (NO) is supposed to be an important neuronal messenger molecule. We investigated the effects of NO-donors such as sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) on noradrenaline (NA) release from rat hippocampus. 1) SNP stimulated [3-H]NA release in the presence of dithiothreitol (DTT) from the prelabeled slices. 2) SNAP stimulated NA release in the presence of L-cysteine or DTT. 3) SNP, SNAP and reducting agents had no stimulatory effect on NA release by themselves. 4) Coaddition of SNAP and L-cysteine stimulated endogenous NA from hippocampus in microdialysis assay. 5) Pretreatment with W-7, calmodulin antagonist, inhibited the effect of NO-donors in a dose-dependent manner. 6) SNP and SNAP stimulated cyclic GMP content in the slices by themselves. 7) The effects of NO-donors on NA release were not modified by the addition of methylene blue or oxyhemoglobin, although the effects on cyclic GMP content were abolished by these agents. These findings suggest that NOdonor stimulated NA release from the hippocampus in cyclic GMP-independent manner.