Ionic currents in hair cells dissociated from frog semicircular canals after preconditioning under microgravity conditions

Author:

Martini Marta,Canella Rita,Leparulo Alessandro,Prigioni Ivo,Fesce Riccardo,Rossi Maria Lisa

Abstract

The effects of microgravity on the biophysical properties of frog labyrinthine hair cells have been examined by analyzing calcium and potassium currents in isolated cells by the patch-clamp technique. The entire, anesthetized frog was exposed to vector-free gravity in a random positioning machine (RPM) and the functional modification induced on single hair cells, dissected from the crista ampullaris, were subsequently studied in vitro. The major targets of microgravity exposure were the calcium/potassium current system and the kinetic mechanism of the fast transient potassium current, IA. The amplitude of ICawas significantly reduced in microgravity-conditioned cells. The delayed current, IKD(a complex of IKVand IKCa), was drastically reduced, mostly in its IKCacomponent. Microgravity also affected IKDkinetics by shifting the steady-state inactivation curve toward negative potentials and increasing the sensitivity of inactivation removal to voltage. As concerns the IA, the I- V and steady-state inactivation curves were indistinguishable under normogravity or microgravity conditions; conversely, IAdecay systematically displayed a two-exponential time course and longer time constants in microgravity, thus potentially providing a larger K+charge; furthermore, IAinactivation removal at −70 mV was slowed down. Stimulation in the RPM machine under normogravity conditions resulted in minor effects on IKDand, occasionally, incomplete IAinactivation at −40 mV. Reduced calcium influx and increased K+repolarizing charge, to variable extents depending on the history of membrane potential, constitute a likely cause for the failure in the afferent mEPSP discharge at the cytoneural junction observed in the intact labyrinth after microgravity conditioning.

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology

Cited by 9 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3