INVOLVEMENT OF NITRIC-OXIDE SYNTHASE IN 3,4-DIAMINOPYRIDINE-EVOKED NORADRENALINE RELEASE IN RAT HIPPOCAMPUS

The release of tritiated noradrenaline, evoked by stimulation of rat h ippocampus slices with 3,4-diaminopyridine (200 muM, 2 min), was enhan ced by the nitric oxide (NO) synthase substrate, L-arginine (but not b y D-arginine), by NO donors (sodium nitroprusside, 3-morpholino-sydnon imine), and by 8-Br-cGMP. The effect of L-arginine was stereospecifica lly antagonized by N(G)-nitro-L-arginine, which given alone was inhibi tory. From these findings we conclude that endogenously formed NO faci litates 3,4-diaminopyridine-evoked noradrenaline release in rat hippoc ampus.