| Aims Evidence suggests that both norepinephrine (NE) and calcitonin gene related peptide (CGRP) participate in the pathology of acute myocardial ischemia. CGRP plays important protective roles in the ischemic and reperfusion injury of the myocardium, but the profiles of potential interactions between CGRP and adrenergic mechanism are still elusive. The aim of this study was to investigate a potential modulation of beta 1 adrenergic receptor (β1-AR) by endogenous CGRP in the early time of acute myocardial ischemia in intact rats.Methods and results An acute myocardial ischemia rat model was used to investigate the changes of the mRNA and protein for theβ1-AR, using quantitative reverse transcription-PCR and Western Blot assays, at 5 min to 60 min following the acute myocardial ischemia induced by coronary artery occlusion. The effects of antagonism of endogenous CGRP orβ1-adrenergic actions by CGRP8-37 or esmolol, on the changes ofβ1-AR were examined. It was observed both the mRNA and protein ofβ1-AR were significantly decreased in the left ventricular ischemic myocardium, by 27.73% and 17.27% respectively, at 15min of myocardial ischemia, compared with the control (P<0.05). The pretreated with CGRP8-37 resulted in the increases of both the mRNA (67.94%, P<0.05) and protein ofβ1-AR (34.05%, P<0.01) following the myocardial ischemia, compared with the controls.Conclusions Theβ1-AR was down-regulated in the early stage of acute myocardial ischemia, which could be reversed by pretreatment with CGRP8-37, indicating endogenous CGRP, a main neurotransmitter of sensory nerves, may down-regulate theβ1-AR in the early time of acute myocardial ischemia.
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