Alteration of Response to Neuropeptide Y in the Nucleus Tractus Solitarius of Spontaneously Hypertensive Rats

Abstract In normotensive rats, microinjections of neu-ropeptide Y (2.5 to 25 ptnol) into the unilateral nucleus tractus solitarius elicited dose-dependent vasodepressor and brady-cardic responses accompanied by an inhibition of sympathetic nerve firing. After microinjections of the a2-adrenergic recep-tor antagonist yohimbine (100 ng) into the nucleus tractus solitarius, the depressor and bradycardic responses to the injection of neuropeptide Y (25 pmol) into the nucleus tractus solitarius were significantly attenuated. In contrast, pretreat-ment with the a,-adrenergic receptor antagonist doxazosin (200 ng) injected into the nucleus tractus solitarius did not alter these responses. In spontaneously hypertensive rats, microinjections of neuropeptide Y (25 pmol) into the nucleus tractus solitarius also elicited depressor and bradycardic re-sponses that were significantly less than those of normotensiv