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The β subunit dominates the relaxation kinetics of heteromeric neuronal nicotinic receptors
Author(s) -
Figl Antonio,
Cohen Bruce N.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00685.x
Subject(s) - time constant , chemistry , relaxation (psychology) , acetylcholine , acetylcholine receptor , nicotinic agonist , biophysics , q10 , nicotinic acetylcholine receptor , receptor , analytical chemistry (journal) , biochemistry , endocrinology , anatomy , chromatography , biology , neuroscience , respiration , engineering , electrical engineering
1 The ACh‐induced voltage‐jump relaxation currents of the nicotinic receptors formed by pair‐wise expression of the rat α2, α3, or α4 subunits with the β2 or β4 subunit in Xenopus oocytes were fitted best by the sum of two exponentials and a constant between ‐60 and ‐150 mV. 2 As the ACh concentration approached zero, the relaxation time constants approached limiting values that should equal the single‐channel burst duration at low ACh concentrations and the synaptic current decay time constants. β4 co‐expression prolonged the zero ACh concentration limits for the relaxation time constants. The fast β4 zero ACh concentration limits ranged from 40 to 121 ms between ‐60 and ‐150 mV, and the slow β4 zero ACh concentration limits ranged from 274 to 1039 ms. In contrast, the fast β2 limits were 4–6 ms over the same voltage range and the slow β2 limits were 30–53 ms. 3 Expression with the β4 subunit increased the voltage sensitivity of the α2, α3 and slow α4 relaxation time constants but not that of the fast α4 relaxation time constant. 4 Reducing the temperature from 22°C to 8–9°C increased the α4β2 and α3β4 relaxation time constants 2.3‐ to 6.6‐fold and reduced the fractional amplitude of the fast relaxation component. It also increased the voltage dependence of the fast α3β4 relaxation time constant and decreased that of the slow time constant. The Q 10 for α4β2 and α3β4 relaxation time constants ranged from 1.9 to 3.9 between 10 and 20°C. 5 The β subunit appears to have a dominant influence on the voltage‐jump relaxation kinetics of heteromeric neuronal nicotinic receptors.