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心脏的起搏受控于一类存在于心脏窦房结被称作If的离子通道，该通道是被细胞膜的超极化所激活. 新近，一类被命名为超极化激活及环化核苷酸调控的阳离子(HCN)通道被克隆. 该家族至少有4个成员，即HCN1～HCN4. 其中2个HCN2和HCN4在心脏有丰富表达. 用异体表达系统表达克隆的HCN2和HCN4通道蛋白，其通道特性类似心脏的天然If通道. 本综述讨论了HCN通道之间的分子结构差异，功能性表达特点以及与它们功能特性有关的分子结构.“,”Cardiac pacemaking is controlled by an inward current called If, which is activated by membrane hyperpolarization of pacemaker cells in the sinoatrial node. Recently, a family of hyperpolarization-activated and cyclic nucleotide-gated cation(HCN) channels comprising at least four members (HCN1－HCN4) has been cloned. Two of these channels, HCN2 and HCN4, are expressed in the heart. When expressed in heterologous cells, HCN2 and HCN4 reveal general features of native If. In the present review we describe the molecular diversity and functional expression of the HCN channels and discuss structural determinants of the channels.