Autoradiographic localization of peptide YY and neuropeptide Y binding sites in the medulla oblongata.

Peptide YY is a highly potent emetic when given intravenously in dogs. We hypothesized that the area postrema, a small brain stem nucleus that acts as a chemoreceptive trigger zone for vomiting and lies outside the blood-brain barrier, might have receptors that PYY would bind to, in order to mediate the emetic response. We prepared [125I]PYY and used autoradiography to show that high affinity binding sites for this ligand were highly localized in the area postrema and related nuclei of the dog medulla oblongata. Furthermore, the distribution of [125I]PYY binding sites in the rat medulla oblongata was very similar to that in the dog; the distribution of [125I]PYY binding sites throughout the rat brain was seen to be similar to the distribution of [125I]NPY binding sites.