Quantitative autoradiographic localization of neuropeptide Y receptors in the rat lower brainstem

Using quantitative autoradiography, we have characterized the binding of 125I-Bolton-Hunter coupled neuropeptide Y ([125I]NPY) and observed the localization of 125I-NPY receptors in the rat lower brainstem. [125I]NPY bound to the receptors in a specific, saturable and reversible manner with high affinity. The binding was blocked only by unlabeled NPY but not by NPY-related peptides i.e. peptide YY, pancreatic polypeptide (avian and human), nor by neurotensin. [125I]NPY receptors were revealed to be coupled to the guanosine triphosphate (GTP)-binding protein. Regional distribution study showed that [125I]NPY has a distinctive pattern of distribution in the rat lower brainstem, being particularly concentrated in the area postrema and the medial subnucleus of the nucleus tractus solitarii. These results suggest that such NPY receptors have an important role in cardiovascular regulation.