Cardiovascular effects of endothelin-1₁₋₃₁ microinjected into the nucleus tractus solitarius of anesthetized rats.

Endothelin-1₁₋₃₁ (ET-1₁₋₃₁) is a 31-amino-acid vasoactive peptide that plays an important role in the regulation of cardiovascular function. However, the cardiovascular effects of central ET-1₁₋₃₁ are still not fully understood. In this study, we assess the effects of ET-1₁₋₃₁ within the nucleus tractus solitarius (NTS) of anesthetized rats and explore the underlying mechanisms of these effects. Bilateral microinjections of ET-1₁₋₃₁ into the NTS produced dose-dependent hypotension and bradycardia, very similar to the effects of a unilateral microinjection of ET-1₁₋₃₁ into the NTS. Bilateral microinjections of ET-1₁₋₃₁ into the NTS significantly decreased baroreflex function in a time-dependent manner. The hypotensive and bradycardic effects induced by the microinjection of ET-1₁₋₃₁ into the NTS were significantly decreased by the ETA receptor antagonist BQ123 and by kynurenic acid, but not by the ETB receptor antagonist BQ788. These results show that ET-1₁₋₃₁ injected into the NTS produces hypotension and bradycardia, mediated by ETA receptors and, at least partly, by the glutamate receptor.