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  • Blockade of 5-HT2 receptors suppresses rate of torque development and motor unit discharge rate during rapid contractions

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    Goodlich527755-Accepted.pdf (1.671Mb)
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    Accepted Manuscript (AM)
    Author(s)
    Goodlich, Benjamin Ian
    Horan, Sean A
    Kavanagh, Justin J
    Griffith University Author(s)
    Kavanagh, Justin J.
    Horan, Sean A.
    Year published
    2021
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    Abstract
    Serotonin (5-HT) is a neuromodulator that is critical for regulating the excitability of spinal motoneurons and the generation of muscle torque. However, the role of 5-HT in modulating human motor unit activity during rapid contractions has yet to be assessed. Nine healthy participants (23.7 ± 2.2 yr) ingested 8 mg of the competitive 5-HT2 antagonist cyproheptadine in a double-blinded, placebo-controlled, repeated-measures experiment. Rapid dorsiflexion contractions were performed at 30%, 50% and 70% of maximal voluntary contraction (MVC), where motor unit activity was assessed by high-density surface electromyographic ...
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    Serotonin (5-HT) is a neuromodulator that is critical for regulating the excitability of spinal motoneurons and the generation of muscle torque. However, the role of 5-HT in modulating human motor unit activity during rapid contractions has yet to be assessed. Nine healthy participants (23.7 ± 2.2 yr) ingested 8 mg of the competitive 5-HT2 antagonist cyproheptadine in a double-blinded, placebo-controlled, repeated-measures experiment. Rapid dorsiflexion contractions were performed at 30%, 50% and 70% of maximal voluntary contraction (MVC), where motor unit activity was assessed by high-density surface electromyographic decomposition. A second protocol was performed where a sustained, fatigue-inducing dorsiflexion contraction was completed prior to undertaking the same 30%, 50% and 70% MVC rapid contractions and motor unit analysis. Motor unit discharge rate (p < 0.001) and rate of torque development (RTD; p = 0.019) for the unfatigued muscle were both significantly lower for the cyproheptadine condition. Following the fatigue inducing contraction, cyproheptadine reduced motor unit discharge rate (p < 0.001) and RTD (p = 0.024), where the effects of cyproheptadine on motor unit discharge rate and RTD increased with increasing contraction intensity. Overall, these results support the viewpoint that serotonergic effects in the central nervous system occur fast enough to regulate motor unit discharge rate during rapid powerful contractions.
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    Journal Title
    Journal of Neurophysiology
    DOI
    https://doi.org/10.1152/jn.00470.2021
    Copyright Statement
    © 2022 American Physiological Society . This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal website for access to the definitive, published version.
    Note
    This publication has been entered as an advanced online version in Griffith Research Online.
    Subject
    Clinical sciences
    Ballistic contraction
    Central fatigue
    Cyproheptadine
    Motoneurone
    Neuromodulation
    Publication URI
    http://hdl.handle.net/10072/411392
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    • Journal articles

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