ABC | Volume 113, Nº3, September 2019

Original Article Imani et al. Sympathetic nervous system and cardioprotection Arq Bras Cardiol. 2019; 113(3):401-408 12 10 8 6 4 2 0 IR St + IR Groups CF (ml/min) Symp + IR Symp + St + IR ** ** ** ** ** ** ** ** End of Baseline End of Ischemia End of Reperfusion Figure 1 – Coronary flow (CF) at the end of baseline, ischemia and reperfusion periods. IR: Ischemia/reperfusion; St: Physical stress; Symp: Symapathectomy. ** p < 0.01 vs baseline phase within the same group. as compared to IR group, while it has been shown significant reduced infarct size as compared with acute physical stress alone (p < 0.01). Effect of acute physical stress on corticosterone level in serum Figure 5 shows the serum level of corticosterone in different groups. Induction of acute physical stress without or with chemical sympathectomy in St and St+Symp+IR groups could increase the amount of serum corticosterone as compared to the IR group, (p < 0.01). Effect of chemical sympathectomy on Systolic blood pressure Figure 6 represents the significant reduction of systolic blood pressure after induction of chemical sympathectomy (p<0.05). Discussion Nowadays daily life is associated with stress that is divided to acute stress and chronic stress, based on exposure duration. 18 Acute stress mediates several neurogenic pathways. 19 Electrophysiological recordings revealed that acute stress manifests good effects such as favour heightened arousal and increases cognitive flexibility in an attentional set- shifting task. 20 In the other view, stress is divided into physical and psychological. A physical stressor such as surgery, trauma and heavy physical activity can trigger many cardiac events. 21 Psychological stress can affect the cardiovascular system through metabolic, inflammatory and hormonal factors. 22,23 In this study, we evaluated the effects of acute physical stress prior to sympathectomy on ischemia-reperfusion injuries in isolated rat heart. The effects of stress Our results showed that induction of acute stress prior to ischemia-reperfusion period led to a decrease in the infarct size, improve hemodynamic parameter and increase in the plasma corticosterone level as compared to IR group and Symp+IR group. Two paradoxical theories have been proposed to explain both advantage and disadvantage effect of stress on the heart. Extremely elevated HR, cardiac contractility and peripheral resistant due to exposure to acute stress can increase the cardiac load and oxygen consumption. In contrast, emerging evidences indicate the opposite effect, for example; cold restraint stress induces cardiac cell protection 24 and it can diminish infarct size as a main parameter of cardiac damage. 25 403