Endogenous CGRP protects retinal cells against stress induced apoptosis in rats

Acute stress can provoke apoptosis of the retina cells, and up-regulation of calcitonin gene related peptide (CGRP) in retina. However the role of CGRP in the pathology of the stress induced apoptosis of the retina cells is still elusive. The aim of this study was to investigate the endogenous of CGRP on retinal cell apoptosis induced by the stress of acute myocardial infarction induced by permanent coronary artery occlusion (CAO) in rats. The acute myocardial infarction model was established by ligating the left anterior descending branch of coronary artery in male Sprague-Dawley rats. The rats were randomized into two groups, the CGRP(8-37) group and a control group, pretreated with CGRP(8-37) (10(-7)mol/L, 1 μL/g, intravenously injected), a specific antagonist of CGRP receptor, and 0.9% saline respectively, at 15 min prior to the CAO. The samples of the retina were collected at 3h of CAO for the assays of TUNEL and caspase-3 activity respectively. The total apoptosis ratio of retinal cells in CGRP(8-37) group was significantly higher than that in the control group (P<0.05). The capase-3 activity was significantly greater in the CGRP(8-37) group, compared with the control group (P<0.05) at 3h of CAO. The vacuolar degeneration of retinal ganglion cells was observed in the CAO animals. The results suggest that the endogenous CGRP may play a protective role in the retinal cell apoptosis induced by the stress of acute myocardial infarction.