Axotomy Increases the Excitability of Dorsal Root Ganglion Cells with
Unmyelinated Axons
Jun-Ming Zhang, David F. Donnelly, Xue-Jun Song, Robert H. LaMotte
Department of Anesthesiology and Department of Pediatrics, Yale University
School of Medicine, 333 Cedar Street, New Haven, CT 06520
APStracts 4:107N, 1997.
ABSTRACT
In order to better understand the neuronal mechanism of neuropathic pain, the
effect of axotomy on the excitability of dorsal root ganglion (DRG) cells with
unmyelinated axons (C cells) was investigated. Whole cell, patch-clamp
recordings were performed on intact dorsal root ganglion (DRG) cells with
intact axons or with axons transected 7-12 days earlier. C cells were
identified by: i) somal size, ii) action potential morphology, iii) conduction
velocity, and iv) in some cases, fast blue injection into the injured nerve
fibers. Axotomy reduced (more negative) action potential threshold but did not
significantly change resting membrane potential, action potential duration or
maximal depolarization rate. Axotomy significantly increased the peak sodium
current, measured under voltage clamp conditions. In fast-blue labelled
(injured) cells, the TTX-sensitive current (TTX-S) was enhanced while the TTX-
resistance (TTX-R) current was reduced. These results suggest that axotomy
increased the excitability of C cells, possibly due to a preferential increase
in expression of TTX-S sodium currents.
Received 4 April 1997; accepted in final form 23 June 1997.
APS Manuscript Number J274-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 15 July 1997