HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 93/1/365    most recent 00804.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Ren, Y. Articles by Lin, Q. Search for Related Content PubMed PubMed Citation Articles by Ren, Y. Articles by Lin, Q.

Sympathetic Modulation of Activity in A- and C-Primary Nociceptive Afferents After Intradermal Injection of Capsaicin in Rats

¹Department of Neuroscience and Cell Biology and ²Division of Neurosurgery, Department of Surgery, University of Texas Medical Branch, Galveston, Texas

Submitted 5 August 2004; accepted in final form 8 September 2004

Neuropathic and inflammatory pain can be modulated by the sympathetic nervous system. In some pain models, sympathetic postganglionic efferents are involved in the modulation of nociceptive transmission in the periphery. The purpose of this study is to examine the sensitization of A- and C-primary afferent nociceptors induced by intradermal injection of capsaicin (CAP) to see whether the presence of sympathetic efferents is essential for the sensitization. Single primary afferent discharges were recorded from the tibial nerve after the fiber types were identified by conduction velocity in anesthetized rats. An enhanced response of some A- and most C-primary afferent fibers to mechanical stimuli was seen in sham-sympathectomized rats after CAP (1%, 15 µl) injection, but the enhanced responses of both A- and C-fibers were reduced after sympathetic postganglionic efferents were removed. Peripheral pretreatment with norepinephrine by intraarterial injection could restore and prolong the CAP-induced enhancement of responses under sympathectomized conditions. In sympathetically intact rats, pretreatment with an ₁-adrenergic receptor antagonist (terazosin) blocked completely the enhanced responses of C-fibers after CAP injection in sympathetically intact rats without significantly affecting the enhanced responses of A-fibers. In contrast, a blockade of ₂-adrenergic receptors by yohimbine only slightly reduced the CAP-evoked enhancement of responses. We conclude that the presence of sympathetic efferents is essential for the CAP-induced sensitization of A- and C-primary afferent fibers to mechanical stimuli and that ₁-adrenergic receptors play a major role in the sympathetic modulation of C-nociceptor sensitivity in the periphery.

This article has been cited by other articles:

				Y. Ren, X. Zou, L. Fang, and Q. Lin Involvement of Peripheral Purinoceptors in Sympathetic Modulation of Capsaicin-Induced Sensitization of Primary Afferent Fibers J Neurophysiol, November 1, 2006; 96(5): 2207 - 2216. [Abstract] [Full Text] [PDF]