THE EFFECT OF SYSTEMIC AND CENTRAL NITRIC-OXIDE ADMINISTRATION ON MILK AVAILABILITY IN LACTATING RATS

THIS study examined the effect of nitric oxide (NO) on milk transfer i n rats. Pups nursed by mothers that received chronic systemic injectio ns of sodium nitroprusside (SNP) weighed significantly less than pups of mothers treated with either saline or N-omega-nitro-L-arginine (NNL A). Intracerebroventricular injection of SNP or L-arginine (L-arg) but not NNLA or saline, caused a significant reduction of milk transfer f rom mother to pups after a 12 h separation period. Systemic oxytocin ( OT) injection reversed the effect of central injection of SNP. Further more, SNP and L-arg inhibited, whereas NNLA permitted the characterist ic milk ejection burst of OT neurones without changing myoepithelial t issue response to systemic OT. These observations suggest that NO may be involved in the regulation of milk ejection bursts and milk transfe r.