期刊
JOURNAL OF PHYSIOLOGICAL SCIENCES
卷 63, 期 2, 页码 133-146出版社
SPRINGER JAPAN KK
DOI: 10.1007/s12576-012-0248-1
关键词
Ca2+ current; Cardiac automaticity; Development; Hyperpolarization-activated cation channel; Heart rate; Sinoatrial node
类别
资金
- Ministry of Education, Culture, Sports, Science and Technology of Japan [22500363, 23136501]
- Grants-in-Aid for Scientific Research [24590268, 23136501, 22500363] Funding Source: KAKEN
Heart rate (HR) of mammalian species changes postnatally, i.e., HR of large animals including humans decreases, while HR in small animals such as mice and rats increases. To clarify cellular mechanisms underlying the postnatal HR changes, we performed in vivo HR measurement and electrophysiological analysis on sinoatrial node (SAN) cells in mice. The in vivo HR was similar to 320 beats min(-1) (bpm) immediately after birth, and increased with age to similar to 690 bpm at postnatal day 14. Under blockage of autonomic nervous systems, HR remained constant until postnatal day 5 and then increased day by day. The spontaneous beating rate of SAN preparation showed a similar postnatal change. The density of the L-type Ca2+ current (LCC) was smaller in neonatal SAN cells than in adult cells, accompanied by a positive shift of voltage-dependent activation. Thus, the postnatal increase in HR is caused by both the increased sympathetic influence and the intrinsic activity of SAN cells. The different conductance and kinetics of LCC may be involved in the postnatal increase in pacemaker activity.
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