Analysis of a slow desensitized state of recombinant adult-type nicotinic acetylcholine receptor channels.
A characteristic feature of the kinetics of nicotinic acetylcholine receptor (nAChR) channels is fast and nearly complete desensitization with a time course between 10 and 100 ms and recovery from desensitization in the range of some hundred ms. In the present study we used a piezo-driven system for ultra-fast solution exchange, analysed the recovery from the fast desensitized state of mouse recombinant adult-type nAChR channels and found no difference to that of embryonic-type channels. By double pulse experiments with application of pulses with a saturating concentration of 1 mm acetylcholine (ACh) with increasing duration of the first pulse and a constant interval between pulses we detected a second slow desensitized state which was entered with a time constant of 2835 ms. Recovery from the slow desensitized state proceeded with a single exponential with a time constant of 16134 ms. The experimental data were interpreted by the addition of a transition from the desensitized state with two bound ACh molecules to a slow desensitized state to the well known circular kinetic scheme of activation and desensitization of nAChR channels. This slow desensitized state might play a role in muscle fatigue or in pathological states like myasthenic syndromes.
Krampfl
K
K
Neurological Department, Hannover Medical School, 31623 Hannover, Germany.
Jahn
K
K
Cordes
A-L
AL
Dengler
R
R
Bufler
J
J
D000109:Acetylcholine / Q000494:pharmacology; D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D006801:Humans; D051379:Mice; D011978:Receptors, Nicotinic / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics
D011978:Receptors, Nicotinic; D011994:Recombinant Proteins; D000109:Acetylcholine