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MIF versus SIF motoneurons, what are their respective contribution in the oculomotor medial rectus pool?
Author/s | Carrero Rojas, Génova
García Hernández, Rosendo Miguel ![]() ![]() ![]() ![]() ![]() ![]() Blumer, Roland Rodríguez de la Cruz, Rosa María ![]() ![]() ![]() ![]() ![]() ![]() ![]() Pastor Loro, Ángel Manuel ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
Department | Universidad de Sevilla. Departamento de Fisiología |
Publication Date | 2021 |
Deposit Date | 2023-11-27 |
Published in |
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Awards | Premio Mensual Publicación Científica Destacada de la US. Facultad de Biología |
Abstract | Multiply-innervated muscle fibers (MIFs) are peculiar to the extraocular muscles as they are non-twitch but produce a slow build up in tension on repetitive stimulation. The motoneurons innervating MIFs establish en grappe ... Multiply-innervated muscle fibers (MIFs) are peculiar to the extraocular muscles as they are non-twitch but produce a slow build up in tension on repetitive stimulation. The motoneurons innervating MIFs establish en grappe terminals along the entire length of the fiber, instead of the typical en plaque terminals that singly-innervated muscle fibers (SIFs) motoneurons establish around the muscle belly. MIF motoneurons have been proposed to participate only in gaze holding and slow eye movements. We aimed to discern the function of MIF motoneurons by recording medial rectus motoneurons of the oculomotor nucleus. Single-unit recordings in awake cats demonstrated that electrophysiologically-identified medial rectus MIF motoneurons participated in different types of eye movements, including fixations, rapid eye movements or saccades, convergences, and the slow and fast phases of the vestibulo-ocular nystagmus, the same as SIF motoneurons did. However, MIF medial rectus motoneurons presented lower firing frequencies, were recruited earlier and showed lower eye position (EP) and eye velocity (EV) sensitivities than SIF motoneurons. MIF medial rectus motoneurons were also smaller, had longer antidromic latencies and a lower synaptic coverage than SIF motoneurons. Peristimulus time histograms (PSTHs) revealed that electrical stimulation to the myotendinous junction, where palisade endings are located, did not recurrently affect the firing probability of medial rectus motoneurons. Therefore, we conclude there is no division of labor between MIF and SIF motoneurons based on the type of eye movement they subserve. |
Funding agencies | Ministerio de Ciencia e Innovación (MICIN). España Austrian Science Fund |
Project ID. | PGC2018-094654-B-100
![]() P32463-B ![]() |
Citation | Carrero Rojas, G., García Hernández, R.M., Blumer, R., Rodríguez de la Cruz, R.M. y Pastor Loro, Á.M. (2021). MIF versus SIF motoneurons, what are their respective contribution in the oculomotor medial rectus pool?. Journal of Neuroscience, 41 (47), 9782-9793. https://doi.org/10.1523/JNEUROSCI.1480-21.2021. |
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