Journal of neurophysiology
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Comparative Study
Steady-state levels of monoamines in the rat lumbar spinal cord: spatial mapping and the effect of acute spinal cord injury.
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 approximately 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. ⋯ 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.