Characterization of calcium-activated chloride channels in patches excised from the dendritic knob of mammalian olfactory receptor neurons.
We investigated the properties of calcium-activated chloride channels in inside-out membrane patches from the dendritic knobs of acutely dissociated rat olfactory receptor neurons. Patches typically contained large calcium-activated currents, with total conductances in the range 30-75 nS. The dose response curve for calcium exhibited an EC50 of about 26 microM. In symmetrical NaCl solutions, the current-voltage relationship reversed at 0 mV and was linear between -80 and +70 mV. When the intracellular NaCl concentration was progressively reduced from 150 to 25 mM, the reversal potential changed in a manner consistent with a chloride-selective conductance. Indeed, modeling these data with the Goldman-Hodgkin-Katz equation revealed a PNa/PCl of 0.034. The halide permeability sequence was PCl > PF > PI > PBr indicating that permeation through the channel was dominated by ion binding sites with a high field strength. The channels were also permeable to the large organic anions, SCN-, acetate-, and gluconate-, with the permeability sequence PCl > PSON > Pacetate > Pgluconate. Significant permeation to gluconate ions suggested that the channel pore had a minimum diameter of at least 5.8 A.
Hallani
M
M
School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia.
Lynch
J W
JW
Barry
P H
PH
D000818:Animals; D000838:Anions; D002118:Calcium / Q000494:pharmacology*; D018118:Chloride Channels / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology; D008322:Mammals; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D000838:Anions; D018118:Chloride Channels; D002118:Calcium