The concentration of nitric oxide was found to be decreased in a hypersympathetic condition. We carried out experiments on cultured sympathetic neurons from 12-14-days-old chick embryos to investigate the role of vasoactive peptides and amine on nitric oxide production. Stimulation of cultured neurons with endothelin-1, norepinephrine and angiotensin-II initially increases nitric oxide production and subsequently decreases it in a dose-dependent manner (P<0.05, n = 7). Stimulation of Fura-2 acetoxymethyl ester-loaded neurons with endothelin-1, norepinephrine and angiotensin-II increases the calcium influx (within 30-90 s) and it is then restored to the initial level (P<0.05, n = 7). An additional observation was that specific stimulator L-arginine significantly increases the nitric oxide release and calcium influx into the cells, whereas N(W)-nitro-L-arginine methyl ester blunts nitric oxide release dose dependently (P<0.05, n = 7) and does not change the calcium concentration in the cells. We propose that vasoactive peptides and amines inhibit nitric oxide production in the cultured sympathetic neuron by regulation of intracellular calcium concentration.