Feedback Effects of Horizontal Cell Membrane Potential on Cone Calcium Currents Studied with Simultaneous Recordings.
From: Dept. of Ophthalmology, Univ. of Nebraska Medical Center, Durham Research Center, Omaha, NE 68198-5840, USA.
Journal of neurophysiology
- Publish Date: Mar 2006
- ISSN: 0022-3077
- Volume: 95
- Issue: 3
- Pages: 1992-5
- Medium: Print
- Language: English
- Citation (JAMA): Cadetti Lucia, Thoreson Wallace B, et al. Feedback Effects of Horizontal Cell Membrane Potential on Cone Calcium Currents Studied with Simultaneous Recordings.. J. Neurophysiol. Mar 2006;95:1992-5
Abstract
Horizontal cell (HC) to cone feedback helps establish the center-surround arrangement of visual receptive fields. It has been shown that HC activity influences cone synaptic output by altering the amplitude and voltage dependence of the calcium current (ICa) in cones. In this study, we obtained voltage-clamp recordings simultaneously from cones and HCs to directly control the membrane potential of HCs and thereby measure the influence of HC membrane potential changes on ICa in adjacent cones. Directly hyperpolarizing voltage clamped HCs produced a negative activation shift and increased the amplitude of ICa in cones. Both of these effects were abolished by enhancing extracellular pH buffering capacity with HEPES. In contrast, addition of the gap junction blocker, carbenoxolone, did not significantly alter the shifts or amplitude changes in cone ICa produced by changes in HC membrane potential. These results support the hypothesis that changes in the HC membrane potential alter the voltage dependence and amplitude of cone ICa by altering extracellular pH levels at the synapse.
Mesh Headings (Keywords): Animals, Calcium, Calcium Signaling, Cells, Cultured, Cones (Retina), Feedback, Hydrogen-Ion Concentration, Membrane Potentials, Patch-Clamp Techniques, Retinal Horizontal Cells, Synaptic Transmission, Urodela
Check for Full Text / PubMed Unique Identifier (PMID): 16371457
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