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This Article Full Text Full Text (PDF) All Versions of this Article: 92/1/567    most recent 01035.2003v1 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 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 (4) Citing Articles via Google Scholar Google Scholar Articles by Noga, B. R. Articles by Hentall, I. D. Search for Related Content PubMed PubMed Citation Articles by Noga, B. R. Articles by Hentall, I. D.

Steady-State Levels of Monoamines in the Rat Lumbar Spinal Cord: Spatial Mapping and the Effect of Acute Spinal Cord Injury

¹The Miami Project to Cure Paralysis, University of Miami School of Medicine, Miami 33101; ²Department of Biomedical Engineering, University of Miami, Miami, Florida 33124; and ³Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford, Illinois 61107-1897

Submitted 27 October 2003; accepted in final form 2 March 2004

Monoamines in the spinal cord are important in the regulation of locomotor rhythms, nociception, and motor reflexes. To gain further insight into the control of these functions, the steady-state extracellular distribution of monoamines was mapped in the anesthetized rat's lumbar spinal cord. The effect of acute spinal cord lesions at sites selected for high resting levels was determined over 1 h to estimate contributions to resting levels from tonic descending activity and to delineate chemical changes that may influence the degree of pathology and recovery after spinal injury. Measurements employed fast cyclic voltammetry with carbon fiber microelectrodes to give high spatial resolution. Monoamine oxidation currents, sampled at equal vertical spacings within each segment, were displayed as contours over the boundaries delineated by histologically reconstructed electrode tracks. Monoamine oxidation currents were found in well defined foci, often confined within a single lamina. Larger currents were typically found in the dorsal or ventral horns and in the lateral aspect of the intermediate zone. Cooling of the low-thoracic spinal cord led to a decrease in the oxidation current (to 71–85% of control) in dorsal and ventral horns. Subsequent low-thoracic transection produced a transient increase in signal in some animals followed by a longer lasting decrease to levels similar to or below that with cooling (to 17–86% of control values). We conclude that descending fibers tonically release high amounts of monoamines in localized regions of the dorsal and ventral horn of the lumbar spinal cord at rest. Lower amounts of monoamines were detected in medial intermediate zone areas, where strong release may be needed for descending activation of locomotor rhythms.

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