Characterization of Calcium-activated Chloride Channels in Patches Excised from the Dendritic Knob of Mammalian Olfactory Receptor Neurons |
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Authors: | M. Hallani J.W. Lynch P.H. Barry |
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Affiliation: | (1) School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia, 2052, AU;(2) Neurobiology Program, Garvan Institute of Medical Research, Darlinghurst, Sydney, NSW, Australia, 2010, AU;(3) Department of Physiology and Pharmacology, University of Queensland, St. Lucia, QLD, Australia, 4072, AU |
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Abstract: | 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 μm. 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 > PSCN > Pacetate > Pgluconate. Significant permeation to gluconate ions suggested that the channel pore had a minimum diameter of at least 5.8 A. Received: 16 April 1997/Revised: 3 October 1997 |
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Keywords: | : Olfactory receptor neuron — Chemosensory transduction — Organic anion — Halide anion — Ca++-activated Cl− channel |
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