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 hippocampus slices with 3,4-diaminopyridine (200 microM, 2 min), was enhanced by the nitric oxide (NO) synthase substrate, L-arginine (but not by D-arginine), by NO donors (sodium nitroprusside, 3-morpholino-sydnonimine), and by 8-Br-cGMP. The effect of L-arginine was stereospecifically antagonized by NG-nitro-L-arginine, which given alone was inhibitory. From these findings we conclude that endogenously formed NO facilitates 3,4-diaminopyridine-evoked noradrenaline release in rat hippocampus.