Hyperpolarization-activated cyclic nucleotide gated (HCN) channels and the current they carry, I_h, are widely and diversely distributed in the central nervous system (CNS). The distribution of the four subunits of HCN channels is variable within the CNS, within brain regions, and often within subcellular compartments. The precise function of I_h can depend heavily on what other channels are co-expressed. In this review, we give an overview of HCN channel structure, distribution, and modulation by cyclic adenosine monophosphate (cAMP). We then discuss HCN channel and I_h functions, where we have parsed the roles into two main effects: a steady effect on maintaining the resting membrane potential at relatively depolarized values, and slow channel dynamics. Within this framework, we discuss I_h involvement in resonance, synaptic integration, transmitter release, plasticity, and point out a special case, where the effects of I_h on the membrane potential and its slow channel dynamics have dual roles in thalamic neurons.

超极化激活的环核苷酸门控 (HCN) 通道及其携带的电流 I _h广泛多样地分布在中枢神经系统 (CNS) 中。HCN 通道的四个亚基的分布在 CNS 内、大脑区域内以及通常在亚细胞隔间内是可变的。_{I h}的精确功能在很大程度上取决于共同表达的其他通道。在这篇综述中，我们概述了 HCN 通道结构、分布和环磷酸腺苷 (cAMP) 的调节。然后我们讨论 HCN 通道和 I _h函数，我们将这些角色解析为两个主要影响：将静息膜电位保持在相对去极化值的稳定影响，以及缓慢的通道动力学。在这个框架内，我们讨论 I _h参与共振、突触整合、递质释放、可塑性，并指出一个特殊情况，其中 I _h对膜电位的影响及其慢通道动力学在丘脑神经元中具有双重作用。