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: 100/2/598    most recent 01231.2007v1 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 PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Taepavarapruk, N. Articles by Soja, P. J. PubMed PubMed Citation Articles by Taepavarapruk, N. Articles by Soja, P. J.

State-Dependent Changes in Glutamate, Glycine, GABA, and Dopamine Levels in Cat Lumbar Spinal Cord

¹Faculty of Pharmaceutical Sciences and ²Department of Psychiatry, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; ³Department of Physiology, Faculty of Medical Science, Naresuan University, Phitsanulok, Thailand; and ⁴Department of Psychiatry, School of Medicine, University of California, Los Angeles, and Sepulveda Veterans Affairs Medical Center, North Hills, California

Submitted 7 November 2007; accepted in final form 16 March 2008

Recent studies have indicated that the glycine receptor antagonist strychnine and the -aminobutyric acid type A (GABA_A) receptor antagonist bicuculline reduced the rapid-eye-movement (REM) sleep-specific inhibition of sensory inflow via the dorsal spinocerebellar tract (DSCT). These findings imply that the spinal release of glycine and GABA may be due directly to the REM sleep-specific activation of reticulospinal neurons and/or glutamate-activated last-order spinal interneurons. This study used in vivo microdialysis and high-performance liquid chromatography analysis techniques to provide evidence for these possibilities. Microdialysis probes were stereotaxically positioned in the L₃ spinal cord gray matter corresponding to sites where maximal cerebellar-evoked field potentials or individual DSCT and nearby spinoreticular tract (SRT) neurons could be recorded. Glutamate, glycine, and GABA levels significantly increased during REM sleep by approximately 48, 48, and 14%, respectively, compared with the control state of wakefulness. In contrast, dopamine levels significantly decreased by about 28% during REM sleep compared with wakefulness. During the state of wakefulness, electrical stimulation of the nucleus reticularis gigantocellularis (NRGc) at intensities sufficient to inhibit DSCT neuron activity, also significantly increased glutamate and glycine levels by about 69 and 45%, respectively, but not GABA or dopamine levels. We suggest that the reciprocal changes in the release of glutamate, glycine, and GABA versus dopamine during REM sleep contribute to the reduction of sensory inflow to higher brain centers via the DSCT and nearby SRT during this behavioral state. The neural pathways involved in this process likely include reticulo- and diencephalospinal and spinal interneurons.