Brain neuropeptide Y mechanisms. Basic aspects and involvement in cardiovascular and neuroendocrine regulation

a) In the hypothalamus, NPY immunoreactive neurons are non catecholamine containing neurons whereas in the medulla oblongata NPY is present in the majority of the catecholamine neurons. NPY immunoreactive neurons in the MO are critically located at the site of the baroreceptor afferents termination. b) High densities of receptors, as indicated by 125I-pNPY binding studies are present in the various subnuclei of the NTS and area postrema. In slice preparations of this region NPY reduces forskolin and phorbolester-induced cAMP accumulation. c) Antagonistic interactions between NPY-and alpha 2-receptors exist in the NTS. d) Neuropeptide Y and adrenaline both lower the mean arterial blood pressure, heart and respiratory rates after central administration. When given together they antagonize the hypotensive but not the respiratory response of each other. e) Central NPY administration leads to alterations in serum levels of corticosterone, aldosterone, angiotensin II, vasopressin, PRL, LH, GH and TSH which are parallel to changes in discrete hypothalamic catecholamine neuronal systems. f) It is proposed that NPY is a transmitter involved in central cardiovascular and neuroendocrine regulation operating in close association with the CA systems. Before the precise role of NPY can be established, however, specific antagonists have to be developed.