The Effect of Polarizing Currents on Unitary Ia Excitatory Post-synaptic Potentials Evoked in Spinal Motoneurones

Overview

Journal J Physiol

Specialty Physiology

Date 1976 Aug 1

PMID 182969

Citations 26

Authors

F R EDWARDS

S J Redman

B Walmsley

Affiliations

Soon will be listed here.

Abstract

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.

Citing Articles

Post-synaptic conductance increase associated with presynaptic inhibition in cat lumbar motoneurones.

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Direct observations on the contacts made between Ia afferent fibres and alpha-motoneurones in the cat's lumbosacral spinal cord.

Brown A, Fyffe R J Physiol. 1981; 313:121-40.

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Relation between shapes of post-synaptic potentials and changes in firing probability of cat motoneurones.

Fetz E, Gustafsson B J Physiol. 1983; 341:387-410.

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Relations among passive electrical properties of lumbar alpha-motoneurones of the cat.

Gustafsson B, Pinter M J Physiol. 1984; 356:401-31.

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The synaptic current evoked in cat spinal motoneurones by impulses in single group 1a axons.

Finkel A, Redman S J Physiol. 1983; 342:615-32.

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