A derivative of amiloride blocks both the light-regulated and cyclic GMP-regulated conductances in rod photoreceptors

Grant Nicol, P. P M Schnetkamp, Y. Saimi, E. J. Gragoe, M. D. Bownds

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Vertebrate rod photoreceptors in the dark maintain an inward current across the outer segment membrane. The photoresponse results from a light-induced suppression of this dark current. The light-regulated current is not sensitive to either tetrodotoxin or amiloride, potent blockers of Na+ channels. Here, we report that a derivative of amiloride, 3',4'-dichlorobenzamil (DCPA), completely suppresses the dark current and light response recorded from rod photoreceptors. DCPA also blocks a cyclic GMP-activated current in excised patches of rod plasma membrane and a cGMP-induced Ca++ flux from rod disk membranes. These results are consistent with the notion that the Ca++ flux mechanism in the disk membrane and the light-regulated conductance in the plasma membrane are identical. DCPA also inhibits the Na/Ca exchange mechanism in intact rods, but at a 5-10-fold-higher concentration than is required to block the cGMP-activated flux and current. The blocking action of DCPA in 10 nM Ca++ is different from that in 1 mM Ca++, which suggests either that the conductance state of the light-regulated channel may be modified in high and low concentrations of Ca++, or that there may be two ionic channels in the rod outer segment membrane.

Original languageEnglish (US)
Pages (from-to)651-669
Number of pages19
JournalJournal of General Physiology
Volume90
Issue number5
StatePublished - 1987
Externally publishedYes

Fingerprint

Retinal Rod Photoreceptor Cells
Amiloride
Cyclic GMP
Light
Membranes
Cell Membrane
Rod Cell Outer Segment
Vertebrate Photoreceptor Cells
Tetrodotoxin
Ion Channels
dimethyl 2,3,5,6-tetrachloroterephthalate

ASJC Scopus subject areas

  • Physiology

Cite this

A derivative of amiloride blocks both the light-regulated and cyclic GMP-regulated conductances in rod photoreceptors. / Nicol, Grant; Schnetkamp, P. P M; Saimi, Y.; Gragoe, E. J.; Bownds, M. D.

In: Journal of General Physiology, Vol. 90, No. 5, 1987, p. 651-669.

Research output: Contribution to journalArticle

Nicol, Grant ; Schnetkamp, P. P M ; Saimi, Y. ; Gragoe, E. J. ; Bownds, M. D. / A derivative of amiloride blocks both the light-regulated and cyclic GMP-regulated conductances in rod photoreceptors. In: Journal of General Physiology. 1987 ; Vol. 90, No. 5. pp. 651-669.
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AU - Schnetkamp, P. P M

AU - Saimi, Y.

AU - Gragoe, E. J.

AU - Bownds, M. D.

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