Single cyclic GMP-activated channel activity in excised patches of rod outer segment membrane

L W Haynes; A R Kay; K W Yau

doi:10.1038/321066a0

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Single cyclic GMP-activated channel activity in excised patches of rod outer segment membrane

Journal article

Peer reviewed

Single cyclic GMP-activated channel activity in excised patches of rod outer segment membrane

L W Haynes, A R Kay and K W Yau

Nature (London), Vol.321(6065), pp.66-70

05/01/1986

DOI: 10.1038/321066a0

PMID: 2422558

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Abstract

The plasma membrane of retinal rod outer segments contains a cyclic GMP-activated conductance which appears to be the light-sensitive conductance involved in phototransduction. Recently, it has been found that this conductance is partially blocked by Mg2+ and Ca2+ at physiological concentrations, thus possibly accounting for the absence of observable single-channel activity in excised membrane patches and for the unusually small apparent unit conductance deduced from noise measurements on intact cells. We now report that, as expected from this idea, single cGMP-activated channel activity can be detected from an excised rod membrane patch in the absence of divalent cations. The most prominent unitary current had a mean conductance of approximately 25 pS. Both individual channel openings (mean open time approximately 1 ms) and short bursts of openings (mean burst duration of about a few milliseconds) were observed. In addition, there were smaller events which probably represented other states of the conductance. The mean current increased with the third power of cGMP concentration, suggesting that there are at least three cGMP-binding sites on the channel molecule. With 0.2 mM Mg2+ in the cGMP-containing solution, a flickering block of the open channel was observed; the effect of Ca2+ was similar. The results resolve a puzzle about the light-sensitive conductance by demonstrating that it is an aqueous pore rather than a carrier.

Membrane Potentials - drug effects

Cyclic GMP - pharmacology

Rod Cell Outer Segment - drug effects

Ion Channels - drug effects

Ion Channels - physiology

Cell Membrane - physiology

Magnesium - pharmacology

Bufo marinus

Animals

Ambystoma

In Vitro Techniques

Photoreceptor Cells - physiology

Rod Cell Outer Segment - physiology

Details

Title: Subtitle: Single cyclic GMP-activated channel activity in excised patches of rod outer segment membrane
Creators: L W Haynes
A R Kay
K W Yau
Resource Type: Journal article
Publication Details: Nature (London), Vol.321(6065), pp.66-70
Publisher: England
DOI: 10.1038/321066a0
PMID: 2422558
ISSN: 0028-0836
eISSN: 1476-4687
Language: English
Date published: 05/01/1986
Academic Unit: Iowa Neuroscience Institute; Biology
Record Identifier: 9983992098902771

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