Alterations in circulating levels and cardiovascular tissue content of neuropeptide Y-like immunoreactivity during the development of deoxycorticosterone acetate-salt hypertension in the rat.

OBJECTIVE: To investigate the modification of plasma and tissue neuropeptide Y-like immunoreactivity (NPY-li) concentrations, in relation to blood pressure and plasma catecholamine levels, during the development of deoxycorticosterone acetate (DOCA)-salt hypertension. METHODS: Mean arterial pressure (MAP), heart rate, tissue and plasma NPY-li levels, and aortic norepinephrine and epinephrine plasma levels were measured in conscious DOCA-salt hypertensive rats treated for 1, 2 and 3 weeks, and in their respective normotensive controls. RESULTS: Both norepinephrine and NPY-li plasma levels increased significantly in parallel with blood pressure during DOCA-salt treatment, so that MAP was significantly correlated with plasma norepinephrine and NPY-li levels in hypertensive rats. Plasma NPY-li levels were also correlated with norepinephrine levels only in hypertensive rats, but were correlated with epinephrine levels only in normotensive animals. Tissue NPY-li content was lower in the mesenteric artery and heart ventricles after 1-3 weeks of DOCA-salt treatment, but the content in the adrenal gland was not significantly different from that in normotensive rats. CONCLUSIONS: In DOCA-salt hypertensive rats, increased plasma NPY-li levels originate primarily from the sympathetic nerves, since those levels were correlated exclusively with circulating norepinephrine levels and they were associated with a reduction in NPY-li content of the heart and mesenteric artery. It is thus possible that the enhanced release of NPY-li from sympathetic nerves could contribute to the rise in blood pressure and to the maintenance of hypertension in this experimental model.