INVOLVEMENT OF THE Y-2 RECEPTOR SUBTYPE IN THE REGULATION OF PROLACTIN GENE-EXPRESSION BY NEUROPEPTIDE-Y IN THE MALE-RAT

In order to determine the influence of neuropeptide Y (NPY) on the bio synthesis of prolactin (PRL), we have studied the effects of NPY and s ome NPY analogs on PRL gene expression in the male rat anterior pituit ary gland. The following peptides (4 mu g/100 g body wt): NPY, peptide YY (PYY), NPY13-36 (a Y-2 receptor agonist) and [Leu(31),Pro(34)]NPY (a Y-1 receptor agonist) were injected into the left lateral ventricle of adult male rats, Control animals received only the vehicle (0.9% N aCl). All the animals were perfused with 4% paraformaldehyde 4 h after injection and processed for in situ hybridization. The intracerebrove ntricular injection of NPY, PYY, and NPY13-36 induced a significant in crease in the hybridization signal (22-40% over control). On the other hand, the Y-1 receptor agonist [Leu(31), Pro(34)]NPY did not influenc e PRL mRNA levels. These data then suggest that activation of the Y-2 NPY receptor subtype at the central level can positively regulate PRL gene expression.