Ionic mechanisms mediating oscillatory membrane potentials in wide-field retinal amacrine cells

被引:26
作者
Vigh, J
Solessio, E
Morgans, CW
Lasater, EM
机构
[1] Univ Utah, Dept Ophthalmol & Visual Sci, John Moran Eye Ctr, Hlth Sci Ctr, Salt Lake City, UT 84132 USA
[2] Univ Pecs, Dept Gen Zool & Neurobiol, Fac Nat Sci, H-7601 Pecs, Hungary
[3] SUNY Upstate Med Ctr, Ctr Vis Res, Syracuse, NY 13210 USA
[4] Oregon Hlth & Sci Univ, Inst Neurol Sci, Beaverton, OR 97006 USA
关键词
D O I
10.1152/jn.00092.2003
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Particular types of amacrine cells of the vertebrate retina show oscillatory membrane potentials (OMPs) in response to light stimulation. Historically it has been thought the oscillations arose as a result of circuit properties. In a previous study we found that in some amacrine cells, the ability to oscillate was an intrinsic property of the cell. Here we characterized the ionic mechanisms responsible for the oscillations in wide-field amacrine cells (WFACs) in an effort to better understand the functional properties of the cell. The OMPs were found to be calcium (Ca2+) dependent; blocking voltage-gated Ca2+ channels eliminated the oscillations, whereas elevating extracellular Ca2+ enhanced them. Strong intracellular Ca2+ buffering (10 mM EGTA or bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid) eliminated any attenuation in the OMPs as well as a Ca2+-dependent inactivation of the voltage-gated Ca2+ channels. Pharmacological and immunohistochemical characterization revealed that WFACs express L- and N-type voltage-sensitive Ca2+ channels. Block of the L- type channels eliminated the OMPs, but omega-conotoxin GVIA did not, suggesting a different function for the N-type channels. The L- type channels in WFACs are functionally coupled to a set of calcium-dependent potassium (K-(Ca)) channels to mediate OMPs. The initiation of OMPs depended on penitrem-A-sensitive (BK) K-(Ca) channels, whereas their duration is under apamin-sensitive (SK) K-(Ca) channel control. The Ca2+ current is essential to evoke the OMPs and triggering the K-(Ca) currents, which here act as resonant currents, enhances the resonance as an amplifying current, influences the filtering characteristics of the cell membrane, and attenuates the OMPs via CDI of the L- type Ca2+ channel.
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收藏
页码:431 / 443
页数:13
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