Single-channel dose-response studies in single, cell-attached patches.
A method for carrying out dose-response studies of ion channel currents in cell-attached patches has been devised. Patch pipettes are filled at the tip with a solution containing one concentration of ligand and then backfilled with another. The concentration of ligand at the membrane is described as a function of time by the equation for diffusion in a cone, allowing response vs. time data to be transformed into a dose-response curve. For Xenopus myocyte cholinergic receptors, examples of the use of this method are given for several concentration-dependent reactions including blockade by the local anesthetic QX-222, activation by acetylcholine, and modulation of current amplitude by sodium ions. Several methods of analyzing the nonstationary channel kinetics are presented, including a pseudo-stationary approach that uses interval likelihood maximization.
Auerbach
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A
State University of New York, Department of Biophysical Sciences, Buffalo 14214.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004625:Embryo, Nonmammalian; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008012:Lidocaine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008433:Mathematics; D008954:Models, Biological; D009132:Muscles / Q000502:physiology*; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014981:Xenopus
D007473:Ion Channels; D011950:Receptors, Cholinergic; C006072:QX-222; D008012:Lidocaine; D012964:Sodium; D000109:Acetylcholine