Sympathetic Nervous System Changes Of Left Ventricle After Acute Stress In Rats

Objectives: Establishing rat stress induced cardiomyopathy model,through acute immobilization stress.Observed(1)cardiac function,morphological injury changes in different parts of left ventricular myocardial and sympathetic activity changes index-heart rate variability;(2)The expression and distribution in different parts of sympathetic nervous system in rats left ventricle after acute stress,including cardiac sympathetic norepinephrine transporter(NET),tyrosine hydroxylase(TH)of cardiac sympathetic nerve and different subtypes of ?-adrenergic receptor(?AR).Study the mean and function of left ventricular sympathetic nervous system changes after acute stress in stress induced cardiomyopathy(SIC).Methods:1 Rats were randomized into experiment group and Sham group,with ether quickly anesthesia,IMO rats fixed in the rat table by back on it;Sham was injected 0.35 mg/g chloral hydrate through the intraperitoneal,mounted in the table after anesthesia.Local anesthesia with 0.5 ml lidocaine in the neck,separating right carotid artery,0.4 F polyethylene pipe via the carotid artery into left ventricle.2 Electrocardiogram and ventricular pressure:powerlab multichannel physiological record instrument monitoring of ECG and ventricular pressure.3 Echocardiography: echocardiography apparatus,probe frequency 12 MHz,detecting the left ventricular apical patterns on long axis.4 Enzyme linked immunosorbent assay detected of plasma cTn I and NE concentration.5 HE stain:fixed the left ventricular and took out,divided into 3 section accord to the sequence of Apex,middle,and bottom,dehydration encapsulation slice operation,microscope observation after hematoxylin-eosin staining.6 Immunohistochemistry observe the distribution and expression of the TH,?1AR and?2AR in left ventricular different parts.7 western blot detected of left ventricular TH,?1AR and ?2AR expression.8 real-time polymerase chain reaction observe the expression of the myocardial ?1,2,3AR mRNA,and NET mRNA in ganglia of sympathetic trunk.Results:1 Compared with Sham group,IMO's heart rate was faster,QT and QTc remarkable prolong(P<0.05),Q wave deeper,R wave amplitude decreased more.2 rats ST down,8 up,3 does not change significantly in IMO.During the experiment,2 rats died,death rate 15.38%.no death in the Sham.2 Compared with Sham group,VLF,NN50,LF significantly lower;SDNN,RMSSD,HF and LF/HF slightly reduced.3 Echocardiographic apical long axis observed IMO's rats left ventricular apical systolic have an almost spherical expansion.4 Compared with Sham,IMO's left ventricular systolic and +dp/dt increased significantly(P<0.05),end-diastolic pressure and-dp/dt reduced(P<0.05),no difference in left ventricular diastolic pressure.5 In ELISA analyses,experimental 30 min NE in IMO were significantly higher than Sham(P<0.05),at 2 h differences disappear.cTn I in IMO was a significant difference compare with Sham at the experimental 30 min,the more significant difference at the 2 h(P<0.05).6 HE staining,nuclei counts in the IMO were more than Sham.From different regional observation,bottom damage is light,apical heavier,also can saw the nuclear fragmentation,eosinophilic cytoplasm.7 immunohistochemistry: from apical to bottom IMO and Sham TH expression gradually increased,in Sham TH expression bottom were higher than apical(P<0.05).No significant difference in IMO.compared with Sham,IMO TH were higher in apical(P<0.05),no difference were observed in bottom and middle.there are no significant difference between the IMO and the Sham of the distribution of NET on different parts of left ventricle.From apical to bottom,?1AR in IMO gradually increased,Sham decreased.?2AR were similar to the ?1AR,induced in the apical compare to Sham(P<0.05).8 western blot: there were no significant difference in IMO and Sham in TH and NET,?1AR expression reduced and ?2AR increased(P<0.05)in IMO compare to the Sham.9 RT-PCR:compared with Sham,NET mRNA average increased 13.51 times in sympathetic ganglia,?1AR m RNA in IMO were reduced,average increased 0.39 times.?2AR mRNA average increased 8.54 times.?3AR mRNA average increased 1.50 times in myocardium tissue.Conclusions:1 The immobilization stress can induce rats' s stress induced cardiomyopathy,there have a closely relationship between severity of myocardial injury and local cardiac sympathetic nerve system activation,autonomic nerve system balance changed after immobilization stress,that is vagus nerve system activity decrease;2 There are differed between norepinephrine transporter distribution and sympathetic innervation in the left ventricle,from base to apex of left ventricle the NET distribution is more evenly,probably having makes sense to maintain stability in the expression of myocardial ?-adrenergic receptors,NET transport direction would be reversed at the early stage of immobilization stress,may contribute to regional myocardial injury.