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Divergent Modulation of Clinical Measures of Volitional and Reflexive Motor Behaviors following Serotonergic Medications in Human Incomplete Spinal Cord Injury

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posted on 2015-08-13, 00:00 authored by Christopher K. Thompson, T. George Hornby
Incomplete spinal cord injury (SCI) can result in profound impairments in volitional strength and reflex excitability, which contribute to loss of function. Human and animal models suggest that disruption of endogenous monoaminergic input, particularly serotonin (5-HT), from supraspinal centers contributes to this impaired motor function following SCI. In the present study, we investigated the effects of 5-HT medications on motor function in individuals with chronic ( > 1 year) SCI. Clinical measures of strength, spasticity/spasms, and walking ability were assessed in 12 individuals with chronic incomplete SCI following acute administration of either 8mg cyproheptadine, a 5-HT antagonist, or 10 mg escitalopram, a selective 5-HT reuptake inhibitor (SSRI), in a double-blinded, randomized, crossover fashion. Results indicated that 5-HT medications modulated both volitional and reflexive behaviors with little change in walking performance; 5-HT antagonist medications depressed clinical measures of strength and spasticity/spasms, whereas SSRIs augmented both strength and spasticity/spasms. These changes are consistent with the dysregulation of 5-HT sensitive spinal neurons following SCI. This understanding may augment clinicians’ awareness of the motor consequences of 5-HT medications.


Funding for the present work was provided through a University of Illinois at Chicago (UIC) doctoral scholarship and Foundation for Physical Therapy Scholarship to Dr. Thompson and National Institutes of Health (NIH)/National Institute of Child Health and Human Development (NICHD) R21-HD046876 and the Craig H. Neilsen Foundation (grant # 36830) to Dr. Hornby.


Publisher Statement

This is a copy of an article published in the Journal of Neurotrauma © 2013 Copyright Mary Ann Liebert, Inc.; Journal of Neurotrauma is available online at:


Mary Ann Liebert


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