Abstract: Objective More and more researchers become focused on myocardial damages after acute brain injury are diverse.Characteristics of myocardial damages after acute brain injury are divere.The mechanism is not clear and there isn't affirmative method of prevention and treatment.It is of important clinical significance to study the mechanism,prevention and treatment to improve prognosis,decrease mortality and increase the number of heart donation.Objectives of this study are to investigate the process of myocardial damage after acute brain injury and to study the effects of 5-HT in plasma and myocardium on myocardial damage after acute brain injury in rat.The study can provide further insights into the relationship between the brain and the heart,and the prevention and treatment of myocardial injury after acute brain injury.Methods Acute brain injury rat model was induced with weight-drop technique.Electrocardiogram,cardiac function,serum CK-MB(heart-type creatine kinase isoenzyme) and morphologic alterations in myocardium were measured to indicate and diagnose the degree of myocardial damage.Electrocardiogram was recorded using twelve leads electro cardiograph.Alterations of cardiac function included ±dp/dtmax,LVDP(left ventricular developed pressure) and LVEDP(left ventricular diastolic end pressure).serum CK-MB was measured using enzyme reaction rate method.The morphologic alterations in myocardium were observed with light and electronic microscopes.5-HT in plasma and myocardium were detected by high performance liquid chromatography-electrical conductivity detector.Rats were divided into sham group and acute brain injury group in the experiment.Alterations were observed at 4 time point including 1 hour,6 hour,24 hour and 48 hour after acute brain injury.Results The cardiac abnormalities after acute brain injury had been shown as below.Incidence of abnormal ECG increased(P<0.05);Positive and negative dp/dtmax and LVDP decreased(P<0.05);LVEDP increased(P<0.05);CK-MB increased(P<0.05).Degeneration,necrosis and hemorrhage of myocardium were observed by light and electronic microscopes,which included increasing and swelling of mitochondria and disruption of cardiac muscle fiber.The most severe myocardial damage happened in 24 hours after ABI.Myocardial systolic dysfunction happened earlier than diastolic dysfunction.Plasma 5-HT increased significantly(P<0.05).Positive correlation was found between 5-HT in plasma and CK-MB(P<0.05).Conclusion Acute brain injury can lead to myocardial damage.5-HT may play an important role in the mechanism of myocardial damage after brain injury.

Key words: acute brain injury, myocardial damage, 5-HT