Quantitative autoradiography of adrenergic, neuropeptide Y and angiotensin II receptors in the nucleus tractus solitarii and hypothalamus of rats with experimental hypertension

Abstract

Catecholamines, neuropeptide Y (NPY) and angiotensin II (Ang II) are known to participate in the central control of blood pressure. However, the modulation of these neurotransmitter receptors in response to a hypertensive stimulus is not appropriately established. The purpose of the present study was to examine binding parameters of α₂-adrenergic, NPY and Ang II receptors in the nucleus tractus solitarii (NTS) and paraventricular hypothalamic nucleus (PVN) following a hypertensive stimulus in the aortic-coarcted rat by means of quantitative receptor autoradiography. No changes were seen in binding parameters of α₂-adrenergic and NPY receptors in the NTS of the hypertensive rat compared to control. However, an increased affinity (54%) of noradrenaline competing for ³H-PAC was seen in the PVN. Moreover, an increased binding (49%) of ¹²⁵I-PYY was also observed in the PVN. The affinity of Ang II for ¹²⁵I-Sar¹Ile⁸-Ang II binding sites was also increased (57%) in the NTS of the hypertensive rat. No changes in the binding parameters of radioactive Ang II were observed in the PVN. The results suggest that systems involved with hypertension like Ang II in the NTS and catecholamines in the PVN might collaborate in the development/maintenance of high blood pressure in the aortic-coarcted rat.