Contribuição do Hipotálamo Dorsomedial nas respostas cardiovasculares ao estresse emocional agudo

Abstract

Evidence indicates that the dorsomedial hypothalamic region (DMH) plays a key role in the organization of the cardiovascular (CV) responses to acute emotional stress. Inhibition of DMH and/or blockade of excitatory amino acid (EAA) receptors in this region attenuate the pressory and taquicardia responses evoked by stress. However, all these effects have been explored in a single stress model (air jet-stress). We evaluated thecontribution of NMDA receptors in the DMH on the CV responses evoked by cage switch stress (CS stress). Under anesthesia (tribromoethanol, 250 mg/kg), Wistar male rats received guide cannulas into DMH. Seven days after, a cannula was inserted into femoral artery for heart rate (HR) and blood pressure (BP) recording. After 24 h, bilateral nanoinjections (100 nL) of vehicle (saline 0.9%, n=7), the GABAA agonist muscimol(100 pmol, n=8) or the NMDA antagonist AP-5 (100 pmol, n=6) were performed into DMH; ten min later, rats were submitted to CS stress. An additional control group was also tested (no injection, intact group, n=9). In the intact group and in the vehicle group CS stress evoked a tachycardic response ( 119±12 bpm and 121±11 bpm) accompaniedby large increases in BP ( 60±2 mmHg and 60±3 bpm, respectively). Tachycardic and pressor responses were markedly reduced by muscimol and AP-5 (musc: HR: 62±7 bpm and MAP: 37±4 mmHg; AP-5: HR: 31±7 bpm and MAP: 39±3 mmHg, P<0.05 vs. vehicle). The number of cardiac arrhythmias was reduced by AP-5 (vehicle: 3,33 vs AP- 5 1,5). Corticosterone and glucose plasma levels were unaffected by CS or any treatment. Data suggest that the DMH is also important for controlling CV responses in other forms of acute emotional stress. Part of this response involves activation of NMDA EAAreceptors.