Journal article
Excitatory drive to spinal motoneurones is necessary for serotonin to modulate motoneurone excitability via 5‐HT2 receptors in humans
The European journal of neuroscience, Vol.59(1), pp.17-35
01/2024
PMID: 37994250
Appears in Recent Faculty of Health Publications
Metrics
1 Record Views
Abstract
Serotonin modulates corticospinal excitability, motoneurone firing rates and contractile strength via 5‐HT2 receptors. However, the effects of these receptors on cortical and motoneurone excitability during voluntary contractions have not been explored in humans. Therefore, the purpose of this study was to investigate how 5‐HT2 antagonism affects corticospinal and motoneuronal excitability with and without descending drive to motoneurones. Twelve individuals (aged 24 ± 4 years) participated in a double‐blind, placebo‐controlled, crossover study, whereby the 5‐HT2 antagonist cyproheptadine was administered. Transcranial magnetic stimulation (TMS) was delivered to the motor cortex to produce motor evoked potentials (MEPs), and electrical stimulation at the cervicomedullary junction was used to generate cervicomedullary motor evoked potentials (CMEPs) in the biceps brachii at rest and during a range of submaximal elbow flexions. Evoked potentials were also obtained after a conditioning TMS pulse to produce conditioned MEPs and CMEPs (100 ms inter‐stimulus interval). 5‐HT2 antagonism reduced maximal torque (p < 0.001), and compared to placebo, reduced unconditioned MEP amplitude at rest (p = 0.003), conditioned MEP amplitude at rest (p = 0.033) and conditioned MEP amplitude during contractions (p = 0.020). 5‐HT2 antagonism also increased unconditioned CMEP amplitude during voluntary contractions (p = 0.041) but not at rest. Although 5‐HT2 antagonism increased long‐interval intracortical inhibition, net corticospinal excitability was unaffected during voluntary contractions. Given that spinal motoneurone excitability was only affected when descending drive to motoneurones was present, the current study indicates that excitatory drive is necessary for 5‐HT2 receptors to regulate motoneurone excitability but not intracortical circuits.
Details
- Title
- Excitatory drive to spinal motoneurones is necessary for serotonin to modulate motoneurone excitability via 5‐HT2 receptors in humans
- Creators
- Tyler T. Henderson - Griffith UniversityJanet L. Taylor - Edith Cowan UniversityJacob R. Thorstensen - The University of QueenslandJustin J. Kavanagh - Griffith University
- Publication Details
- The European journal of neuroscience, Vol.59(1), pp.17-35
- Publisher
- Wiley
- Number of pages
- 19
- Grant note
- Open access publishing facilitated by Griffith University, as part of the Wiley - Griffith University agreement via the Council of Australian University Librarians.
- Identifiers
- 991013386432502368
- Copyright
- © 2023 The Authors.
- Academic Unit
- Faculty of Health
- Language
- English
- Resource Type
- Journal article