Acute myocardial ischemia up-regulates substance P in the retina of rats.

Abstract

Evidence indicates that sympathetic nerves and substance P (SP) are involved in some physiological and pathophysiological changes and activities in retina. The aim of this study was to investigate whether SP participates in the stress reaction and possible involvement of adrenergic mechanisms in modulation of the changes of SP in the retina of the rats suffering from acute stress evoked by coronary artery occlusion (CAO). The changes of SP in retina were examined and analyzed within 6h of CAO using immunohistochemistry, in situ hybridization and EIA approaches. The effects of phentolamine, an antagonist of alpha1-adrenergic receptor, and esmolol, an antagonist of beta1-adrenergic receptor, on the changes of SP were investigated to examine the role of adrenergic mechanisms in modulation of expression of SP in the retina under the stressful condition. It was observed that SP was markedly up-regulated in the layers of ganglion cells, inner plexiform, inner nuclear and pigment epithelium within 6h of the CAO. Intravenous administration of the adrenergic antagonists attenuated the up-regulation of SP. The results may indicate that SP in retina was involved in the stress response induced by acute myocardial ischemia. Adrenergic mechanisms may modulate the process in the retina.