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Alteration of the fast excitatory postsynaptic current by barium in voltage‐clamped amphibian sympathetic ganglion cells
Author(s) -
Connor E.A.,
Parsons R.L.
Publication year - 1984
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.1476-5381.1984.tb10116.x
Subject(s) - barium , excitatory postsynaptic potential , biophysics , bullfrog , postsynaptic potential , hyperpolarization (physics) , sympathetic ganglion , membrane potential , depolarization , chemistry , postsynaptic current , materials science , inhibitory postsynaptic potential , endocrinology , biology , biochemistry , receptor , stereochemistry , inorganic chemistry , nuclear magnetic resonance spectroscopy
1 Barium‐induced alterations in fast excitatory postsynaptic currents (e.p.s.cs) have been studied in voltage‐clamped bullfrog sympathetic ganglion B cells. 2 In the presence of 2–8 m m barium, e.p.s.c. decay was prolonged and in many cells the e.p.s.c. decay phase deviated from a single exponential function. The decay phase in these cases was more accurately described as the sum of two exponential functions. The frequency of occurrence of a complex decay increased both with increasing barium concentration and with hyperpolarization. 3 Miniature e.p.s.c. decay also was prolonged in barium‐treated cells. 4 E.p.s.c. amplitude was not markedly affected by barium (2–8 m m ) in cells voltage‐clamped to — 50 mV whereas at — 90 mV there was a progressive increase in peak size with increasing barium concentration. 5 In control cells the e.p.s.c.‐voltage relationship was linear between −20 and −100 mV; however, this relationship became progressively non‐linear with membrane hyperpolarization in barium‐treated cells. The e.p.s.c. reversal potential was shifted to a more negative value in the presence of barium. 6 There was a voltage‐dependent increase in charge movement during the e.p.s.c. in barium‐treated cells which was not present in control cells. 7 We conclude that the voltage‐dependent alteration in e.p.s.c. decay time course, peak amplitude and charge movement in barium‐treated cells is due to a direct postsynaptic action of barium on the kinetics of receptor‐channel gating in postganglionic sympathetic neurones.