NITRIC-OXIDE PROLONGS PARTURITION AND INHIBITS MATERNAL-BEHAVIOR IN RATS

WE examined the effect of nitric oxide (NO) on the process of parturit ion in rats. Subcutaneous injection of the NO donor sodium nitroprussi de (SNP) in late pregnancy prolonged the total parturition time. The e ffect of N omega-nitro-L-arginine was not significantly different from that of saline. Intracerebroventricular injection of SNP in parturien t rats delayed the progress of parturition. Both modes of SNP treatmen t also inhibited expression of maternal behaviour. Central injection o f oxytocin (OXT) with SNP failed to reduce parturition time significan tly, but intrapartum, not postpartum, maternal behaviour was restored. These observations suggest that NO interferes with the release of OXT within the brain, hence affecting the initiation of maternal behaviou r, and may also impair oxytocin secretion from the neurohypophysis.