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A slowly inactivating K+ current in retinal ganglion cells from postnatal rat

Published online by Cambridge University Press:  02 June 2009

Nikolaus J. Sucher  and
Stuart A. Lipton
Nikolaus J. Sucher
Affiliation:
Laboratory of Cellular and Molecular Neuroscience, Department of Neurology, Children's Hospital, Beth Israel Hospital, Brigham and Women's Hospital, Massachusetts General Hospital, and the Program in Neuroscience, Harvard Medical School, Boston
Stuart A. Lipton
Affiliation:
Laboratory of Cellular and Molecular Neuroscience, Department of Neurology, Children's Hospital, Beth Israel Hospital, Brigham and Women's Hospital, Massachusetts General Hospital, and the Program in Neuroscience, Harvard Medical School, Boston
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Abstract

The whole-cell configuration of the patch-clamp technique was used to study voltage-gated K+ conductances in retinal ganglion cells from postnatal rat. Retinal ganglion cells were fluorescently labeled in situ, dissociated from the retina, and maintained in culture. With physiological solutions in the bath and the pipette, depolarizing voltage steps from physiological holding potentials activated Na+-(INa), Ca2+ (ICa), and K+ -currents studied previously in retinal ganglion cells. Here we report on a slowly decaying K+ current, not heretofore reported in rat. With 4-AP, TEA, and Co2+ in the bath, to block IA, IK, and IK(Ca), respectively, a slowly decaying outward current was activated from —80 mV by steps positive to —40 mV. This current was present in 92% of all ganglion cells tested (n = 83). It activated within 10 ms and inactivated with a voltage-independent time constant of about 70 ms at 35°C. Inactivation was voltage-dependent, half-maximal at —55 mV, and almost complete at 0 mV. The current was blocked by internal Cs+ and TEA, or by external application of 1 mM Ba2+, but not by 3 mM extracellular Co2+. The biophysical and pharmacological properties of this current are distinctly different from those of slowly inactivating K+ currents studied in other rat neurons. It was very similar, however, to a slowly inactivating K+ current previously reported in ganglion cells of tiger salamander retina. This last finding indicates conservation of a defined K+ channel type in functionally related cells in both lower vertebrates and mammals.

Keywords

RetinaGanglion cellsPatch clampCell cultureRat
Type
Short Communication
Information
Visual Neuroscience , Volume 8 , Issue 2 , February 1992 , pp. 171 - 176
Copyright
Copyright © Cambridge University Press 1992

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