The Journal of Neurophysiology Vol. 77 No. 3 March 1997, pp. 1447-1459
Copyright ©1997 The American Physiological Society

Electrogenic Hyperpolarization-Elicited Chloride Transporter Current in Blue Cones of Zebrafish Retinal Slices

Shih-Fang Fan and Stephen Yazulla

Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York 11794-5230

Fan, Shih-Fang and Stephen Yazulla. Electrogenic hyperpolarization-elicited chloride transporter current in blue cones of zebrafish retinal slices. J. Neurophysiol. 77: 1447-1459, 1997. Voltage-activated currents in blue cones of the retinal slice of zebrafish were characterized using whole cell recording techniques. Depolarizing-elicited currents were recorded: an outward tetraethylammonium (TEA)-sensitive K⁺ current (I_Kx), an outward Ca²⁺-activated Cl current (I_Cl(Ca)), from which we inferred an inward Ca²⁺ current (I_Ca) as well as a hyperpolarizing-elicited nonselective inward cation current (I_h). In addition, hyperpolarizing steps elicited an outward current (I_out-h) in about one-third of the blue cones. I_out-h seems to be carried by inward transported Cl because it was abolished by equimolar substitution of bath Cl with acetate; equimolar substitution of Na⁺ with choline or TEA had no effect; it was not affected by Cl channel blockers, anthracene-9-carboxylic acid, 4,4-diisothiocyanostilbene-2,2-disulfonic acid, N-phenylanthranilic acid (DPC), niflumic acid, and 4-acetamido-4-isothiocyanostilbene-2,2-disulfonic acid but was suppressed by Cl transporter blockers acetalzolamide, bumetanide, N-ethylmaleimide, furosemide, and vanadate, and no reversal potential was found. In addition, this current was suppressed by ouabains but unrelated to their Na⁺-K⁺-ATPase inhibitory effect, was not suppressed by Co²⁺ or nifedipine, was not affected by the gap junction decoupler, 2-octanol, was increased by bath application of Cs⁺, presumably due to suppression of I_h, which was masked by I_out-h, and was suppressed by intense light. Similar current also was found in the short cones and double cones. As I_out-h operates over the same voltage range, and with similar magnitude and time course as I_h, we suggest that I_out-h contributes to the modulation of the photoresponse of cones.