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The sinus node itself also plays a role in heart rate slowing down during postnatal development

Yang Zhifang, Li Cizhen, Li Qian, Wang Xijin, Liu Yuanmou

Department of Physiology, Shanghai Second medical University.Shanghai(200025)

Abstract

The slowing down mechanism of heart rate during growth of the body after birth was studied in isolated rabbit heart and sinus node (SN) preparation with langendorff perfusion method, conventional was also used to measure the concentration of cAMP within SN cells. The results indicate that without the influence of nervous and humoral factors, the spontaneous heart rate would also become slower as the rabbit grew older, which is due to the decrease of spontaneous depolarized rate of phase 4 in SN cells. The negative-directed shift of the threshold potential of I_f and the decrease in cAMP concentration within SN cells may be responsible for the phenomenon. The results obtained suggest that besides the nervous and humoral factors which influence the heart rate, the changes in automaticity of SN cell itself may take part in the slowing down process as the body grows up.

Key words: Patch clamp;Sinus node;Pacemaker current;Heart rate

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Citing This Article：

Yang Zhifang, Li Cizhen, Li Qian, Wang Xijin, Liu Yuanmou. The sinus node itself also plays a role in heart rate slowing down during postnatal development. Acta Physiol Sin 2002; 54 (4): (in Chinese with English abstract).