Depolarization induced facilitation of a plateau generating current in
ventral horn neurons in the turtle spinal cord.
Gytis Svirskis and Jørn Hounsgaard
Jørn Hounsgaard, Department of Medical Physiology, The PANUM Institute,
Bldg. 12-5-9, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N,
Denmark., Tel: + 45 35 32 75 59 Fax: + 45 35 32 74 99
APStracts 4:0077N, 1997.
ABSTRACT
Plasticity at the neuronal level commonly involves use-dependent changes in
strength of particular synaptic pathways or regulation of postsynaptic
properties by modulatory transmitters. Here we analyze a novel form of short-
term plasticity mediated by use- dependent facilitation of postsynaptic
responsiveness. Using current and voltage clamp recordings, we found that all
spinal ventral horn neurons able to generate plateau potentials showed
depolarization induced facilitation of the underlying inward current.
Facilitation was noticeable when depolarized to more than -50 mV at intervals
less than 4 s. When stimulating with fast triangular voltage ramps, the inward
current activated at a less depolarized potential during the second ramp. The
inward current and facilitation was eliminated by nifedipine, a selective
antagonist of L-type calcium channels. Depolarization induced facilitation of
low-voltage activated L-type calcium channels is suggested to be the
underlying mechanism. It is noted that facilitation occurs on a time scale
compatible with a role in phasic motor activity.
Received 1997 May 23; accepted in final form 1997 May 27.
APS Manuscript Number J062-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 11 June 1997