The effect of lactation on nitric oxide synthase gene expression.

Nitric oxide-synthesizing (NOS) enzyme has been identified in several neural populations, including the hypothalamic paraventricular nucleus (PVN). The PVN plays a major role in regulating milk ejection. In the present study, using in situ hybridization, the effect of lactation on NOS mRNA in the PVN was investigated. A significant increase was seen in the PVN of lactating rats, indicating a possible involvement of nitric oxide in the hypothalamic-pituitary regulation of milk ejection.