Abstract: Objective To understand effects of norepinephrine(NE), 5-hydroxytryptamine(5-HT) and 5-HT_2AR on myocardial damage occurred after acute brain injury(MDABI) through studying role of 5-HT_2ARB in the MDABI and its effect on endogenous NE and 5-HT and to provide further insights into the relationship between the brain and the heart, and the prevention and treatment of MDABI. Methods A rat model of acute brain injury(ABI) was established. ECG, cardiac function(CF), creatine kinase MB(CK-MB) in serum and morphologic changes in myocardium were measured to indicate the degree of myocardial damage. NE and 5-HT in plasma and myocardium were detected by high performance liquid phase chromatography with electrochemical detection(HPLC-ECD). Expression of 5-HT_2AR was determined by RT-PCR and real-time RT-PCR. There were four groups in the experiment including normal, sham, ABI and 5-HT_2ARB group，with 8 rats in each group. Indicators were observed 24 hours after ABI. Results The cardiac abnormalities after acute brain injury included abnormal ECG increased(P<0.05); ventricular systolic and diastolic dysfunction included ±dp/dtmax and left ventricular developed pressure(LVDP) decreased(P<0.05), left ventricular diastolic end pressure(LVDEP) increased(P<0.05); CK-MB increased(P<0.05). Degeneration, necrosis and hemorrhage of myocardium were observed under light and electronic microscope. NE in plasma and myocardium and plasma 5-HT increased significantly(P<0.05). 5-HT_2ARB was beneficial in reducing degree of MDABI and could reduce myocardial NE(P<0.05). Conclusion ABI can lead to myocardial damage. It maybe happen through increasing 5-HT to activate 5-HT_2AR. 5-HT_2ARB can reduce the MDABI.

Key words: acute brain injury, myocardial damage, 5-HT_2ARB, noradrenaline, 5-hydroxytryptamine