Is the human masticatory system devoid of recurrent inhibition?
Date
2007
Authors
Turker, Kemal Sitki
Schmied, Annie
Rossi, A.
Mazzocchio, R.
Sowman, Paul Fredrick
Vedel, J. P.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Experimental Brain Research, 2007; 179 (1):131-144
Statement of Responsibility
K. S. Türker, A. Schmied, A. Rossi, R. Mazzocchio, P. F. Sowman and J. P. Vedel
Conference Name
Abstract
The aim of the present study was to investigate the existence or otherwise of a functional recurrent inhibitory system (Renshaw cell system) in the motoneurons that innervate human masticatory muscles. In a previous study, l-acetylcarnitine (l-Ac), a substance known to potentiate recurrent inhibition in humans was found to alter, in a specific way, the discharge variability, and the synchronous activity of motor units depending on the presence or absence of recurrent inhibition in the corresponding motoneuron pool. Using a similar paradigm, we have recorded the tonic discharge activity of motor unit pairs from the masseter muscle during voluntary isometric contraction while subjects were undergoing continuous intravenous saline (SAL, NaCl 0.9%) perfusion. Following a brief baseline-recording period, the subjects were given a test injection of either l-Ac or isotonic saline (SAL) in a double blind manner. The variability, synchronization, and coherence between the motor unit discharges were analysed during three successive periods: pre-injection, during injection, and post-injection, each lasting 2–3 min. Neither l-Ac nor SAL injection induced a significant change in the inter-spike interval (ISI) or the coefficient of variation of the ISIs in the motor units tested. There were also no significant changes in the pattern of synchronous activity or in the coherence, which reflects the common frequency content of the unit discharges. Reminiscent of what had been observed previously with motoneurons without recurrent inhibition in the Abductor Digitorum Minimi muscle, the lack of effects of l-Ac injection on the firing behaviour of masseter motoneurons may suggest that classical Renshaw cell inhibition is lacking in this motoneuron pool.
School/Discipline
School of Molecular and Biomedical Science
Dissertation Note
Provenance
An erratum for this article has been published. Please click on the description link below to view the erratum.
Description
The original publication is available at www.springerlink.com