目的 探讨超极化激活环核苷酸门控阳离子通道4(HCN4)在不同发育时期大鼠心肌组织中各类细胞的表达规律，为进一步研究HCN4对心肌的作用提供形态学依据。方法 出生1 d、1月、3月、6月健康SD大鼠各15只。取新鲜心脏，石蜡切片和冷冻切片，利用免疫组织化学和荧光技术观察不同发育时段大鼠心肌组织HCN4阳性细胞的表达分布情况及形态学特征。利用Western blotting 技术观察左右心室HCN4的蛋白含量。 结果 免疫组织化学和荧光染色结果显示，HCN4阳性细胞在出生后1 d、1月、3月、6月的血管平滑肌细胞，心内膜和血管的内皮细胞，心外膜的间皮细胞、成纤维细胞，大量心房肌细胞和少量心室肌细胞、传导组织细胞均有表达，但不同部位的表达细胞数量不均；Western blotting结果显示，心室HCN4蛋白随着月龄的增加表达逐渐降低。 结论 HCN4在大鼠心肌组织中的表达随年龄的增加逐渐下降，但增殖能力较强的细胞持续存在，提示HCN4可能对心肌组织中的多种细胞的生存起调控作用。

Objective To investigate the changes of hyperpolarization-activated cyclic nucleotide gated cation channels 4(HCN4) expression in the rat heart at different developmental stages and to provide morphological basis for further study of HCN4 on cardiac function. Methods Four groups of rats, 15 rats per group, which were separately born for 1 day, 1 month, 3 months and 6 months were used in this study. The hearts of each group were collected. Paraffin section and frozen section were used to observe the distribution and morphological characteristics of HCN4 positive cells in myocardium of rats at different developmental stages by immunohistochemistry and fluorescence techniques. The protein content of HCN4 in left and right ventricles was observed by Western blotting. Results The immunohistochemical and fluorescence results showed that HCN4 positive cells in 1 day after birth, 1 month, 3 months and 6 months of the vascular smooth muscle cells, endocardial and vascular endothelial cells, epicardial mesothelial cells, fibroblasts, a large number of atrial myocytes, a small amount of cardiomyocytes, and conduction of tissue cells were expressed, but the number of expressed cells was uneven in different parts. Western blotting results showed that the expression of ventricular HCN4 protein decreased with age. Conclusion The expression of HCN4 decreased gradually with the increase of age in the rat myocardium, but the cells with strong proliferative ability are sustained expression. These results suggest that HCN4 may regulate the survival of many cells in myocardium.