INHIBITION OF NERVE STIMULATION-INDUCED VASODILATATION IN CORPORA CAVERNOSA OF THE PITHED RAT BY BLOCKADE OF NITRIC-OXIDE SYNTHASE

1 The effect of inhibition of nitric oxide synthase by N(G)-nitro-L-arginine methyl ester (L-NAME) on nerve stimulation-induced vasodilatation in corpora cavernosa was studied in the pithed rat. Corporal vasodilatation was estimated by the increase in ratio (corpora cavernosal pressure/systemic blood pressure; CP/BP) following electrical stimulation of the sacral part of the spinal cord. 2 L-NAME (2, 5, 10 and 25 mg kg-1) caused an increase in BP and a dose-dependent inhibition of the rise in the CP/BP ratio following stimulation. 3 The inhibitory effect of L-NAME (25 mg kg-1) on the corporal response to spinal cord stimulation, as well as the pressor response, was partially prevented by prior administration of L- but not D-arginine (400 mg kg-1, i.v.). 4 L-NAME (20 mg kg-1, i.v.) did not inhibit the rise in corporal pressure resulting from direct intracavernosal administration of papaverine (400 mug over 2 min). However, this response was inhibited by 5-hydroxytryptamine (20 mug kg-1, i.v.). 5 The results are indicative of a role of nitric oxide (NO) in the corporal vasodilator response to erectile stimulation.