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The effect of polarizing currents on unitary Ia excitatory post‐synaptic potentials evoked in spinal motoneurones.
Author(s) -
Edwards F R,
Redman S J,
Walmsley B
Publication year - 1976
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 - 10.1113/jphysiol.1976.sp011490
Subject(s) - depolarization , hyperpolarization (physics) , excitatory postsynaptic potential , neuroscience , membrane potential , chemistry , synaptic potential , neurotransmission , biophysics , nuclear magnetic resonance , physics , biology , inhibitory postsynaptic potential , stereochemistry , biochemistry , nuclear magnetic resonance spectroscopy , receptor
1. Depolarizing and hyperpolarizing currents were applied to motoneurones in which unitary Ia e.p.s.p.s were evoked. The results concentrate on those e.p.s.p.s which had time courses which were compatible with somatically located synapses. 2. No reversal of these e.p.s.p.s was observed. Depolarizing currents up to 150 nA simply reduced the peak amplitude. 3. Hyperpolarizing currents caused little, if any, increase in the peak amplitude of the e.p.s.p. The time course of decay became briefer as the membrane was hyperpolarized. 4. Changes in decay time course of the e.p.s.p. which accompanied depolarization and hyperpolarization could be attributed to changes in membrane conductances, rather than to changes in synaptic current time course. 5. The failure of the e.p.s.p. to increase with hyperpolarization was shown to be due to the failure of the synaptic current to increase, rather than to the shunting of anomalous rectification. 6. Chemical and electrical transmission are evaluated against these results and those of the preceding papers.