Intraperitoneal injection of pilocarpine (0.75-3.0 mg/kg) caused a dose-rel
ated seminal emission in adult male rats. The seminal emission response to
3 mg/kg of pilocarpine was greatly reduced in atropinized (5 and 10 mg/kg,
SC) animals, suggesting a cholinomimetic effect. N-w-nitro-L-arginine methy
l ester (5, 10, and 20 mg/kg, SC), a nitric oxide synthesis inhibitor, also
inhibited the pilocarpine-induced seminal emission, which was reversed by
L-arginine (600 mg/kg, SC) or by coinjection of sodium nitroprusside (0.5 m
g/kg, SC). Urine analysis for levels of nitric oxide metabolites, nitrate/n
itrite (NO3-/NO2-), showed marked alterations in accordance with the drug t
reatments. The results suggest that nitric oxide mediates the inhibitory ne
urotransmission responsible for seminal emission in pilocarpine stimulated
rats. (C) 2000 Elsevier Science Inc. All rights reserved.