NEUROPEPTIDE-Y INCREASES THE CORTICOTROPIN-RELEASING FACTOR MESSENGER-RIBONUCLEIC-ACID LEVEL IN THE RAT HYPOTHALAMUS

Neuropeptide Y (NPY) has a stimulatory effect on adrenocorticotropin ( ACTH) and corticotropin-releasing factor (CRF) release. In the present study, to investigate the effect of NPY on CRF synthesis, the effect of centrally administered NPY on CRF messenger RNA (mRNA) levels in ra t hypothalamus was examined under pentobarbital anesthesia. The admini stration of 0.01, 0.1 and 1 nmol of NPY into the lateral ventricle dos e-dependently Increased the plasma ACTH levels, as well as the levels of proopiomelanocortin mRNA in the anterior pituitary. The CRF mRNA le vel in the hypothalamus also increased after administration of 0.1 and 1 nmol of NPY in a dose-dependent manner. The administration of 3 nmo l of phentolamine or propranolol failed to block 0.1 nmol NPY-induced ACTH release or 1 nmol NPY-stimulated CRF mRNA levels in the hypothala mus. These results Indicate that the central administration of NPY inc reases the CRF mRNA levels in the hypothalamus and the probable CRF re lease, which increases the proopiomelanocortin mRNA levels and ACTH se cretion in the anterior pituitary. Therefore, NPY seems to play a phys iological role in the regulation of the release and synthesis of CRF i n the hypothalamus.