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Ion Channels and Excitable Membranes

開催日 2014/9/11
時間 16:00 - 17:00
会場 Poster / Exhibition(Event Hall B)

Current Clamp Analysis of Low-voltage-activated Ca2+ Current in Avian Nucleus Laminaris

  • P1-010
  • 深谷 亮太 / Ryota Fukaya:1 山田 玲 / Rei Yamada:1 久場 博司 / Hiroshi Kuba:1,2 
  • 1:名古屋大院・医・細胞生理 / Dept Cell Physiol, Nagoya Univ, Aichi, Japan 2:JST さきがけ / JST PRESTO 

Interaural time difference (ITD) is a cue for sound localization and first determined with the mechanism of binaural coincidence detection at nucleus laminaris (NL) in birds. Neurons in NL are tuned to a specific frequency of sound, characteristic frequency (CF) and vary in morphology and expression of ion channels depending on their CF. In this study, we investigated low-voltage-activated (LVA) Ca2+ channels in NL neurons using whole-cell patch clamp recordings in chick brainstem slice preparation. In current clamp recordings, we found that NL neurons exhibited rebound depolarization (hump) after hyperpolarizing currents and it was prominent in low CF NL neurons. Importantly, this hump was observed under the blockades of Ih and INa, suggesting a contribution of LVA Ca2+ channels to the hump. The hump was significant when the resting membrane potential was held above -70 mV, and the amplitude increased in proportion to the size of preceding hyperpolarization. The hump appeared when hyperpolarization exceeded -60 mV and was saturated near -100 mV. In addition, the hump was triggered by a short (less than 50 ms) hyperpolarizing current. These characteristics of the hump, such as activation and inactivation around resting membrane potential and rapid kinetics, are similar to the properties of LVA Ca2+ channels. Indeed, the hump was diminished by application of LVA Ca2+ channel blockers, confirming the existence of LVA Ca2+ channels in low CF NL neurons. Notably, low CF NL neurons exhibit longer dendrites than higher CF neurons. This may suggest that LVA Ca2+ channels contribute to the computation of binaural inputs in dendrites of low CF NL neurons.

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