Microinjections of subpicomolar amounts of NPY(13–36) into the nucleus tractus solitarius of the rat counteract the vasodepressor responses of NPY(1–36) and of a NPY Y 1 receptor agonist

Abstract

Microinjections of neuropeptide Y (NPY) (1–36) and of the NPY Y 1 agonist [Leu 31, Pro 34]NPY into the caudal dorsomedial part of the nucleus tractus solitarius (Sol) in the anaesthetized rat led to the development of dose-related vasodepressor and bradycardic responses. The threshold dose of the NPY Y 2 agonist NPY(13–36) (50 fmol) significantly counteracted the vasodepressor actions of a close to ED 50 dose of NPY(1–36) (2.5 pmol) and of the NPY Y 1 agonist (5 pmol). These results indicate that NPY Y 1 receptor activation in the Sol leads to the development of a vasodepressor response, which can be counteracted by NPY Y 2 receptor activation in the Sol. The results support the existence of a Y 2/Y 1 receptor-receptor interaction in the Sol, via which NPY Y 2 receptors may reduce transduction over NPY Y 1 receptors.