QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

This Article Full Text Full Text (PDF) Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in 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 Web of Science (14) Citing Articles via Google Scholar Google Scholar Articles by Foo, H. Articles by Mason, P. Search for Related Content PubMed PubMed Citation Articles by Foo, H. Articles by Mason, P.

 Previous Article  |  Next Article 

The Journal of Neuroscience, March 1, 2003, 23(5):1933

Discharge of Raphe Magnus ON and OFF Cells Is Predictive of the Motor Facilitation Evoked by Repeated Laser Stimulation

H. Foo and Peggy Mason

Department of Neurobiology, Pharmacology and Physiology, and Committee on Neurobiology, University of Chicago, Chicago, Illinois 60637

Medullary raphe magnus (RM) ON and OFF cells are thought to modulate spinal nociception by gating withdrawals evoked by noxious stimulation. To test whether withdrawal initiation is the target of RM modulation, we examined the relationship between ON and OFF cell discharge and motor withdrawal evoked by noxious laser heat in halothane-anesthetized rats. The cellular responses of both cell types began during the 50 msec after onset of the tail flick, peaked within 200 msec, and outlasted the duration of the motor reaction. Thus, it is unlikely that the target of ON and OFF cell modulation is withdrawal initiation; instead, ON and OFF cells may modulate reactions to repeated noxious stimulation. We therefore tested whether laser heat-evoked changes in RM cell discharge were predictive of the modulatory effects of one noxious stimulus on the reaction to a subsequent noxious stimulus. Two pulses of laser heat were presented at interpulse intervals of 0.8, 2.0, or 10.0 sec. The motor withdrawal evoked by the second pulse was significantly enhanced relative to that evoked by the first pulse. The observed motor enhancement depended on supraspinal input because it was not present in spinalized rats. Comparison of the relative changes in motor and cellular activity preceding double laser heat stimulation revealed parallel changes between motor facilitation, decreases in OFF cell discharge, and increases in ON cell discharge. This finding suggests a preparatory role for RM ON and OFF cells in enhancing reactions to a noxious stimulus that closely follows another noxious stimulus.

Key words: pain; CO₂ laser; motor facilitation; rats; ventromedial medulla; electrophysiology

---

Copyright © 2003 Society for Neuroscience  0270-6474/03/2351933-08$05.00/0

This article has been cited by other articles:

				K. M. Hellman, T. S. Brink, and P. Mason Activity of Murine Raphe Magnus Cells Predicts Tachypnea and On-Going Nociceptive Responsiveness J Neurophysiol, December 1, 2007; 98(6): 3121 - 3133. [Abstract] [Full Text] [PDF]

				H. Foo and P. Mason Movement-Related Discharge of Ventromedial Medullary Neurons J Neurophysiol, February 1, 2005; 93(2): 873 - 883. [Abstract] [Full Text] [PDF]

				M. M. Heinricher and M. J. Neubert Neural Basis for the Hyperalgesic Action of Cholecystokinin in the Rostral Ventromedial Medulla J Neurophysiol, October 1, 2004; 92(4): 1982 - 1989. [Abstract] [Full Text] [PDF]

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help