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Effect of tetramethylpyrazine on the responses of respiration and expression of nNOS in brainstem to hypoxia in rats

Li Zicheng, Li Li, Yan Hengxiu, Hu Haiyan, Ma Yuqiong, Yang Wenxing, Chen Li, Zheng Yu

Department of Physiology,West China School of Preclinical and Forensic Medicine,Sichuan University.Chengdu 610044,Sichuan；China；Department of Histology and Embryology, West China School of Preclinical and Forensic Medicine,Sichuan University.Chengdu 610044,Sichuan

Abstract

The aim of the present study was to investigate the effect of tetramethylpyrazine(TMP) on the changes of respiration and expression of nNOS in brainstem induced by hypoxia in the rats. Hypoxia was induced by inhalation of 8% O_(2)-balanced N_(2).The electromyogram(EMG) of diaphragm was monitored to evaluate the respiratory response of the rats to hypoxia. The immunohistochemical staining technique was used to study the change of the expression of nNOS in the brainstem during hypoxia. In the hypoxia group of rats,a successive process of response,excitatory followed by inhibitory,was produced.At 20min after hypoxia,a significant inhibition of respiration occurred,which was characterized with a marked decrease in the inspiratory duration,the respiratory frequency,and the amplitude of inspiration and a prolongation of expiratory duration(P<0.05).In the rats pretreated with TMP, the respiratory activity was not obviously depressed(P>0.05).In the hypoxia group of rats,the level of nNOS immunoreactivity was enhanced remarkably in the lateral reticular nucleus,nucleus of trapezoid,hypoglossal nucleus and the facial nucleus compared with the control group(P<0.05).In the rats pretreated with TMP,the nNOS level increased further in the nuclei montioned above(P<0.05). The results obtained indicate that TMP can reverse the inhibitory effect of hypoxia on respiration in the rats and that nNOS may be involved in the respiratory protective action of TMP.

Key words: hypoxia;Respiration;electromyogram;Ligustrazine;Rat

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Citing This Article：

Li Zicheng, Li Li, Yan Hengxiu, Hu Haiyan, Ma Yuqiong, Yang Wenxing, Chen Li, Zheng Yu. Effect of tetramethylpyrazine on the responses of respiration and expression of nNOS in brainstem to hypoxia in rats. Acta Physiol Sin 2005; 57 (2): (in Chinese with English abstract).