Deactivation and desensitization of mouse embryonic- and adult-type nicotinic receptor channel currents.
Recombinant nicotinic acetylcholine receptor (nAChR) channels transiently expressed in HEK293 cells were investigated using the patch-clamp technique in the cell-attached and outside-out modes for single-channel analysis and ultra-fast agonist application to multiple channels. Deactivation (current decay after removal of agonist) and desensitization (current decay in the presence of agonist) were analyzed at embryonic- (gamma) and adult-type (epsilon) nAChR channels. Time constants of desensitization were similar for both receptor types (epsilon: 53.1+/-16.9 ms; gamma: 49.2+/-15.7 ms) and corresponded to the mean duration of clusters of single channel openings activated by pulses of 1 mM ACh. Deactivation showed distinct characteristics. Time constants were 1.76+/-0.16 ms for epsilon- and 3.19+/-0.18 ms for gamma-nAChR channels, corresponding to mean burst duration analyzed from single channels in the same preparation (epsilon: 1.85+/-1.2 ms, gamma: 3.85+/-2.1 ms). It is assumed that differences in deactivation are of functional relevance at the muscle endplate.
Jahn
K
K
Department of Neurology, Ludwig-Maximilians University of Munich, Klinikum Grosshadern, Marchioninistrasse 15, 81377, Munich, Germany. Klaus.Jahn@lrz.uni-muenchen.de
Mohammadi
B
B
Krampfl
K
K
Abicht
A
A
Lochmüller
H
H
Bufler
J
J
D000109:Acetylcholine / Q000494:pharmacology; D000367:Age Factors; D000818:Animals; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D005333:Fetus; D006801:Humans; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000196:embryology* / Q000378:metabolism; D018722:Nicotinic Agonists / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D014162:Transfection
D007473:Ion Channels; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D000109:Acetylcholine