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Biphasic effect of pentobarbitone on chick myotube nicotinic receptor channel kinetics
Author(s) -
Liu Guo Jun,
Madsen Barry W.
Publication year - 1996
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1996.tb15549.x
Subject(s) - chemistry , acetylcholine receptor , nicotinic agonist , kinetics , biophysics , receptor , acetylcholine , nicotinic acetylcholine receptor , patch clamp , allosteric regulation , time constant , mechanism of action , pharmacology , biochemistry , biology , in vitro , physics , quantum mechanics , electrical engineering , engineering
1 The modulatory action of pentobarbitone on chick myotube nicotinic acetylcholine receptor kinetics was studied by the patch clamp technique, particularly focussing on effects at low concentrations. 2 Open time sojourn distributions of foetal‐type receptors recorded at room temperature (22–24°C) in cell‐attached mode in the presence of 0.2 μ m acetylcholine were well described by two exponentials, with fast and slow time constants of 0.53 ± 0.12 and 16.7 ± 2.2 ms (mean ± s.e.mean) respectively. 3 The duration of the slow open time constant was increased by low concentrations of pentobarbitone (up to 1 μ m ), and thereafter decreased with higher concentrations (10–50 μ m ) in a concentration‐dependent manner. 4 Complementary evidence for the stimulatory effect of pentobarbitone on open time was obtained (i) by using a backfill technique where drug concentration at the patch gradually increases over time, and (ii) through use of perfused outside‐out preparations where receptors in the same patch were successively exposed to acetylcholine in the absence and presence of pentobarbitone. 5 The dual action of pentobarbitone on channel kinetics probably indicates that an allosteric interaction mechanism is involved rather than simple steric channel blockade.