| In the past three decades, five types of natriuretic peptide (NPs) and receptors (NPRs) have been foundin heart, brain and some other tissues. ANP, BNP, CNP and NPR-A, NPR-B, NPR-C receptors were foundin mammalian tissues. The heart’s overload, hypopiesia and hypoxia environment, adrenalin, isoprel andphenylephrine were the main elements that lead to NPs secretion. In addition, NPs play an important role inregulating the heart and renal function and sustaining the homeostasis, with the function include in diuresis,depressing the blood pressure, regulating the nerves, promoting the osseous development, in particular.Recent research showed that, the concentration of BNP in blood increased quickly in the patients sufferedin acute myocardial infarction, congestive heart failure and cardiac muscle hypertrophy, and this specificchange have become a biomarker of heart failure, and the synthetic NPs have been used in the treatment onacute decompensation heart failure and some other disease.According to the present data, in the brain, NPRs generally distributed in the cholinergic andcatecholaminergic neurons that participated in the cardiovascular regulation, such as hypothalamus,periaqueductal gray, nuclei tegmentales, nucleus ceruleus, dorsal nucleus of vagus nerve, hypoglossalnucleus, reticular formation, nucleus of solitary tract, ambiguous nucleus. Besides, data from the culturedcells have confirmed that the binding of NPs and NPR could suppress the release of catecholamine andacetylcholine transmitter, thus increase its uptake. Clinical observation showed that, both the sympatheticand parasympathetic nerve activity reduced before and after myocardial ischemia, but the mechanism isstill unclear.The author presume that the sudden rise of BNP in the patient’s blood maybe suppress the activity ofcardiovascular center in medulla oblongata through the NPRs, then result in the functional decrease ofautonomic nerve. Therefore, to investigate the possible mechanism of NPs and NPRs in cardiovascularnerve regulation, this study use the SD rats as experimental subjects, reproduce the acute myocardialischemia model by ligating the left anterior coronary. TTC staining technique will be used to assess weatherthe reproductive model was successful. Weather the TH and ChAT masccline neuron in brain stem expressNPR will be observed by immunofluorescence double labeling technique. And Western Blot method will beused to examine the expression of NPRs in the cardiovascular region of accommodation in hindbrain.The results were as follows:①There were many TH positive neuron express NPR-A and NPR-C in the nucleus that related to the cardiovascular function closely;②Many ChAT positive neuron in the ratbrain express NPR-A and NPR-C;③The TTC staining result demonstrated that the method of ligating theleft anterior coronary can duplicate the rat modle of acute myocardial ischemia successfully, and thesuccess ratio was96.6%, the urine output increased significantly in the previous three days after operation;④The expression of NPR-C in kidney cortex was lower than the control group, and was higher than thecomparison afterward; But the expression of NPR-A has been lower than the comparison;⑤Compared tothe control group, the expression of NPR-A in nucleus tractus solitarius increased but the expression ofNPR-C decreased significantly;⑥The expression of NPR-A has been higher than the control group inrostral medulla oblongata, however, it tend to be decreased from the third day; The expression of NPR-Cincreased from the3rd day, and was significantly higher than the control group in the14-18th day, andrecuperated by the normal level on the28day. The TH expression quantity has been lower than the controlgroup; The expression of ChAT is higher than the comparison slightly in the3rd day, then has been lowerthan the comparison;⑦In the caudal medulla oblongata, the expression of NPR-A is higher than thecomparison only on the3rd day and the18th day afteroperation; but the expression of NPR-C, TH, ChAThas been lower than the comparison from the third to28th day.The conclusions of these results were as follows:1. TH positive neurons that related to the cardiovascular function in the normal rat hindbrain expressNPR-A and NPR-C; ChAT positive neurons in ambiguous nucleus and some other nucleus could expressNPR-A and NPR-C; these results showed that the natriuretic peptide could regulate the activities of TH andChAT positive neuron with the NPR-A and NPR-C.2. It maybe one of the negative feedback mechanism on regulating the renal function that theexpression of NPR-A decreased and the NPR-C increased; The increasing expression of NPR-A in thecaudal and rostral medulla oblongata and the nucleus tractus solitarius may strengthen the function of BNP.Thus, the reduced expression of TH and the ChAT maybe was the result, which suppress the sympatheticand the parasympathetic activity.These results provide some basic information for further revealing of the neural mechanisms ofnatriuretic peptide regulate the central system after myocardial ischemia, and provide some theoretical datato the prevention and treatment of acute myocardial infarction. |
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