To detect the effect of nitric oxide (NO)on basal and reflex release of oxytocin (OT),L-arginine(the substrate of NO synthase )and NG-nitro-L-arginine methyl ester (L-NAME,NO synthase inhibitor)were intracerebroventricularly(icv)administrated into the pentobarbital anesthetized rats and the plasma OT level was detected with radioimmunoassay.Injection (icv) of L-arginine(100 g/L,10 μL,n=8)and L-NAME (54.0 g/L,5 μL,n=12) had no significant effect on OT basal secretion.However,the elevated OT secretion in response to hypotension induced by intravenous infusion of sodium nitroprusside was dose-dependently augmented by icv injection of 5 μL L-NAME (dose 1:27.0 g/L,n=9；dose 2:54.0 g/L,n=8).The results indicate that L-NAME does not change basal OT secretion,but enhances OT reflex secretion evoked by hypotension,which suggests that NO may act as an inhibitory factor on reflex release of OT.