LOCALIZATION OF NEUROPEPTIDE-Y IMMUNOREACTIVITY AND [I-125] PEPTIDE YY BINDING-SITES IN THE HUMAN PITUITARY

High levels of neuropeptide Y (NPY) are found in the hypothalamus, med ian eminence, pituitary portal blood, and the pituitary in a number of species. Neuropeptide Y may influence the synthesis and secretion of a variety of hormones by interacting with specific receptors in the hy pothalamus and/or the pituitary. To further define the function of NPY in the pituitary, we have examined the distribution of NPY immunoreac tivity and NPY receptors in sections of human pituitary using immunohi stochemical and autoradiographic techniques. Neuropeptide Y-immunoreac tive varicose axons were seen throughout the neural lobe. A moderate n umber of NPY-immunoreactive cells were found in the anterior lobe. A v ery high level of [I-125]PYY binding was seen in the neural lobe with low levels in the anterior lobe. The binding in the neural lobe was in hibited by NPY(13-36) at a K-i of 5.3 nM and [Leu(31)-Pro(34)]NPY at a K-i of 390 nM, indicating the receptor was the Y-2 subtype. Therefore , neuronally released NPY may modulate human neural lobe function thro ugh a Y-1 receptor.