NGF and hereditary pheochromocytoma-paraganglioma: The present study aimed to investigate the role of HCN channels in sympathetic nerve differentiation using PC12 cells which are derived from rat pheochromocytoma and have the ability of acquiring sympathetic neuron features in response to NGF (Hu et al., 2018; Terada et al., 2018), including neurite outgrowth (Peng et al., 2009) which is an important morphological feature and a key cellular process during neuronal differentiation (Vaudry et al., 2002).