Antagonism of 5-HT 2 receptors attenuates self-sustained firing of human motor units

5-HT receptors on motoneurones play a critical role in facilitating persistent inward currents (PICs). Although facilitation of PICs can enhance self-sustained firing after periods of excitation, the relationship between 5-HT receptor activity and self-sustained firing in human motor units (MUs) has...

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Bibliographic Details
Published in:The Journal of physiology 2024-04, Vol.602 (8), p.1759-1774
Main Authors: Goodlich, Benjamin I, Pearcey, Gregory E P, Del Vecchio, Alessandro, Horan, Sean A, Kavanagh, Justin J
Format: Article
Language:English
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Summary:5-HT receptors on motoneurones play a critical role in facilitating persistent inward currents (PICs). Although facilitation of PICs can enhance self-sustained firing after periods of excitation, the relationship between 5-HT receptor activity and self-sustained firing in human motor units (MUs) has not been resolved. MU activity was assessed from the tibialis anterior of 10 healthy adults (24.9 ± 2.8 years) during two contraction protocols. Both protocols featured steady-state isometric contractions with constant descending drive to the motoneurone pool. However, one protocol also included an additional phase of superimposed descending drive. Adding and then removing descending drive in the middle of steady-state contractions altered MU firing behaviour across the motor pool, where newly recruited units in the superimposed phase were unable to switch off (P = 0.0002), and units recruited prior to additional descending drive reduced their discharge rates (P 
ISSN:0022-3751
1469-7793
DOI:10.1113/JP285867