Changes of myocardial norepinephrine after cerebral ischemia and the effect of reperfusion on its expression

Objective To investigate changes of the expression of myocardial norepinephrine (NE)during cerebral ischemia and the effect of reperfusion on its expression.Methods Rats were randomly allocated into three groups:sham operation group,cerebral ischemia group and cerebral ischemia/reperfusion(I/R)group.The area of cerebral ischemia,concentration of serum CK-MB,content of myocardial NE and pathological changes of the myocardium were determined respectively for the cerebral ischemia group and I/R group(0,6,12,24,48 and 72h).Results The ischemic focus could be observed 6h after cerebral ischemia and its area reached the peak value at 12h;the concentration of serum CK-MB increased gradually after cerebral ischemia,peak at 12h and later on,gradually declined; the content of myocardial NE peaked at 6h and began to decline at 12h.The cerebral necrotic area declined evidently after cerebral I/R;the peak time of the serum CK-MB concentration was unchanged, but concentrations after I/R were evidently higher than that in the cerebral ischemia group at 6 and 12h; the peak time of myocardial NE was unchanged and the high level remained until 48h.Pathological changes of the myocardium included inflammatory cell infiltration,endocarditis,myofibrosis and focal necrosis etc;large area of myocardial necrosis could be observed occasionally.The total incidence rate of myofibrosis and focal necrosis increased evidently after cerebral I/R.Conclusion Cerebral ischemia with comparatively larger area may induce excessive release of NE from sympathetic nerves,which could result in secondary myocardial injury.Cerebral I/R can protect brain tissues,but increases myocardial NE release,which thus aggravates myocardial injury.