Development of purinergic sensitivity in sensory neurons after peripheral nerve injury in the rat

Citation
Jl. Zhou et al., Development of purinergic sensitivity in sensory neurons after peripheral nerve injury in the rat, BRAIN RES, 915(2), 2001, pp. 161-169
Citations number
61
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences & Behavoir
Journal title
BRAIN RESEARCH
ISSN journal
0006-8993 → ACNP
Volume
915
Issue
2
Year of publication
2001
Pages
161 - 169
Database
ISI
SICI code
0006-8993(20011012)915:2<161:DOPSIS>2.0.ZU;2-S
Abstract
Purinoceptors are present in the cell bodies as well as in both peripheral and central terminals of many sensory neurons, where they may play a role i n sensory transmission, including pain. After peripheral nerve injury at th e spinal nerve level, some axotomized afferent neurons develop ongoing disc harges (ectopic discharges) that originate in the dorsal root ganglion (DRG ). In the present study, we attempted to determine whether or not purinergi c sensitivity develops in injured sensory neurons which display ectopic dis charges, as well as in silent units. The L-4 and L-5 spinal nerves were lig ated in Sprague-Dawley rats. Four to 21 days after the surgery, the DRGs wi th attached dorsal roots and spinal nerves were removed and ectopic dischar ges were recorded from teased dorsal root fascicles using an in vitro recor ding set-up. The results showed that 75.6 and 65.1% of the chronically axot omized DRG neurons displaying ectopic discharges enhanced their activity af ter application of adenosine 5'-triphosphate (ATP, I mM) or alpha,beta -met hylene ATP (mATP, 100 muM), respectively. In addition, application of these purinoceptor agonists evoked activity in 7 of 28 axotomized DRG neurons, w hich did not show ongoing discharges. In contrast, only I of 34 DRG neurons acutely isolated from normal rats (no previous spinal nerve ligation) resp onded to either mATP or ATR In most of the tested units. mATP-induced enhan cement of ectopic discharges was blocked by non-specific P2X receptor antag onists, PPADS or suramin. The data from the present study suggest that puri nergic sensitivity develops in DRG neurons after chronic axotomy and that t his purinergic sensitivity is likely to be mediated by P2X purinoceptors. T his acquired purinergic sensitivity may play an important functional role i n the enhancement of ectopic discharges and exacerbation of pain upon sympa thetic activation in the neuropathic pain state. (C) 2001 Elsevier Science BY All rights reserved.