Alpha1 and alpha2 adrenoceptors in the medial amygdaloid nucleus have different role on cardiovascular responses to acute restraint stress in rats

Abstract

Introduction and GoalsMedial amygdaloid nucleus (MeA) is involved in the modulation of the cardiovascular responses during exposure by restraint stress (RS). We investigate the involvement of the alpha‐adrenoceptors into the MeA therein mediate cardiovascular responses to RS in rats.MethodsWe used Wistar rats. It was done implanting bilateral guide cannula into the MeA to microinjections of drugs or vehicle. The animals received a polyethylene catheter into the femoral artery for blood pressure (BP) recording.ResultsThe RS caused BP and heart rate (HR) increases in aCSF treated animals (n=8). RX821002 (alpha2‐ adrenoceptor antagonist) treatment significantly enhanced restraint‐evoked HR increase without significant effect on the BP response, when compared with control animals (ΔMAP: F1,66= 3,496, P= 0,0660, n=5; ΔHR: F1,66= 15,22, P= 0,0002, n=5; twoway ANOVA). In contrast, the treatment with WB4101 (alpha1‐adrenoceptor antagonist) significantly reduced restraint‐evoked HR increase without significant effect on the BP response, when compared with control animals (ΔMAP: F1,66= 0,8556, P= 0,3583, n=5, and ΔHR: F1,66= 3,558, P= 0,0637, n=5; two‐way ANOVA).ConclusionResults suggest that adrenoceptors either alpha(1) and alpha(2) have different roles into the MeA on the HR increase evoked by RS, enhance and reducing the cardiac responses.Financial Support: CNPq, CAPES.