ABC | Volume 113, Nº3, September 2019

Original Article Imani et al. Sympathetic nervous system and cardioprotection Arq Bras Cardiol. 2019; 113(3):401-408 IR St + IR Groups Symp + IR Symp + St + IR 40 45 30 20 10 15 25 35 0 5 IS/AAR (%) * && Figure 4 – The percentage of infracts size (IS/AAR %). IR: Ischemia/reperfusion; St: Physical stress; Symp: Symapathectomy. * p < 0.05 compared to IR, && p < 0.01 compared to St+IR. IR 1400 ** ** 1200 1000 800 600 400 200 0 St + IR Groups Symp + St + IR Corticosterone (ng/ml) Figure 5 – Corticosterone level in serum. IR: Ischemia/reperfusion; St: Physical stress; Symp: Symapathectomy. ** p<0.01 compared to IR. In this regard, Abe et al. demonstrated that acute stress attenuates ischemia-reperfusion injury in the kidney through the activation of sympathetic and anti-inflammatory pathway. 26 Moreover, exposure to intermediate stress involves in cell protection against subsequent lethal ischemia, as a concept, preconditioning phenomenon. 27,28 It seems that acute physical stress exposure as a preconditioning agent protects the heart against I/R. We observed an increase in RPP and LVDP amounts due to acute stress induction in St+IR group as compared with IR group that indicates acute stress would trigger mechanisms to prepare the body for suitable responses to stimuli because the improvement of the cardiac function is important. Therefore, it seems that the effectiveness of stress induction is associated with; 1. nature of the stressor, 2. stress episode duration, 3. intensity of the stimulus and 4. stress predictability or unpredictability. In fact, each of the above factors effects on the neural and hormonal responses to stress. Our results showed that corticosterone is elevated after stress induction, and in Symp+St+IR group is higher than the IR group. It is well established that stress enhances the activity of the HPA axis which results to increase corticosterone secretion 22,29 that can be protective as it prepares the organism to deal with challenges. Based on our results sympathectomy did not effect on stress-induced elevated corticosterone possibly because stress affects HPA axis through different mechanisms such as changes in metabolic and inflammatory factors in addition to increased sympathetic nervous system. 22 Furthermore, this hormone induces changes in immune cells redistribution that enhance immune function. 30 We showed that infarct size is decreased in St+IR group in comparison to the IR group and 405