DEVELOPMENTAL INCREASE IN HYPERPOLARIZATION-ACTIVATED CURRENT REGULATES INTRINSIC FIRING PROPERTIES IN RAT VESTIBULAR GANGLION CELLS

作者：Yoshimoto R; Iwasaki S^*; Takago H; Nakajima T; Sahara Y; Kitamura K

来源：Neuroscience, 2015, 284: 632-642.

DOI：10.1016/j.neuroscience.2014.10.034

• hyperpolarization-activated current
• vestibular ganglion
• development

The primary vestibular neurons convey afferent information from hair cells in the inner ear to the vestibular nuclei and the cerebellum. The intrinsic firing properties of vestibular ganglion cells (VGCs) are heterogeneous to sustained membrane depolarization, and undergo marked developmental changes from phasic to tonic types during the early postnatal period. Previous studies have shown that low-voltage-activated potassium channels, Kv1 and Kv7, play a critical role in determining the firing pattern of VGCs. In the present study, we explored the developmental changes in the properties of hyperpolarization-activated current (I-h) in rat VGCs and the role played by I-h in determining the firing properties of VGCs. Tonic firing VGCs showed a larger current density of I-h as compared to phasic firing VGCs, and tonic firing VGCs became phasic firing in the presence of ZD7288, an I-h channel blocker, indicating that I-h contributes to control the firing pattern of VGCs. The amplitude of I-h increased and the activation kinetics of I-h became faster during the developmental period. Analysis of developmental changes in the expression of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels revealed that expression of HCN1 protein and its mRNA increased during the developmental period, whereas expression of HCN2-4 protein and its mRNA did not change. Our results suggest that HCN1 channels as well as Kv1 channels are critical in determining the firing pattern of rat VGCs and that developmental up-regulation of HCN1 transforms VGCs from phasic to tonic firing phenotypes.

• 出版日期2015-1-22