Effects of leptin on fasting-induced inhibition of neuronal nitric oxide synthase mRNA in the paraventricular and supraoptic nuclei of rats

Fasting induced a reduction in neuronal nitric oxide synthase (nNOS) mRNA in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of rats. The effect of intracerebroventricular (i.c.v.) administration of leptin on the nNOS mRNA level in the PVN and SON of fasting rats was studied by in situ hybridization histochemistry. Leptin (10 mu g/kg b.wt) or vehicle was administered i.c.v. at 1700 h on two successive days fasting for 2 days. Fasting for 2 days with i.c.v. administration of vehicle induced a significant reduction of nNOS mRNA:in the PVN and SON. Central administration of leptin prevented the fasting-induced reduction of nNOS mRNA in the PVN and SON. Administration of leptin also prevented the fasting-induced reductions of thyrotropin-releasing hormone (TRH) and corticotropin-releasing hormone (CRH) mRNAs in the parvocellular division of the PVN. These results suggest that leptin is associated with fasting-induced reduction of nNOS mRNA in the PVN and SON as well as TRH and CRH mRNAs in the PVN. (C) 1999 Published by Elsevier Science B.V. All rights reserved.