Rat α‐ and γ‐motoneuron soma size and succinate dehydrogenase activity are independent of neuromuscular activity level
- 14 May 2007
- journal article
- research article
- Published by Wiley in Muscle & Nerve
- Vol. 36 (2), 234-241
- https://doi.org/10.1002/mus.20810
Abstract
The chronic level of neuromuscular activity, that is, activation and loading, strongly influences the morphological, metabolic, phenotypic, and physiological properties of skeletal muscles. The effects on the innervating motoneurons, however, are less established. We determined and compared the effects of 30 days of decreased activity (induced by a complete mid‐thoracic spinal cord transection, ST) or near inactivity (induced by spinal cord isolation, SI) on the soma size and succinate dehydrogenase (SDH) activity of motoneurons innervating a predominantly slow ankle extensor (soleus) and a predominantly fast ankle flexor (tibialis anterior) muscle of adult rats. Soleus and tibialis anterior motoneuron pools were labeled retrogradely using nuclear yellow. The α‐ and γ‐motoneurons were classified based on soma size. Mean number of labeled motoneurons, and mean soma size and SDH activity for both α‐ and γ‐motoneurons were similar in control, ST, and SI rats. Compared to previous reports showing significant decreases in muscle fiber size and adaptations toward a “faster” metabolic profile following ST and SI, the results indicate that, unlike the muscles they innervate, the motoneurons are relatively unresponsive to chronic reductions in neuromuscular activity. The implication of these results is that mean size and SDH activity are independent of the number of action potentials generated by both α‐ and γ‐motoneurons and that even the absence of afferent input to the spinal cord has no influence on size and oxidative metabolic potential of the motoneuron soma. Muscle Nerve, 2007Keywords
This publication has 92 references indexed in Scilit:
- Changes in ??-Motoneuron Properties with Altered Physical Activity LevelsExercise and Sport Sciences Reviews, 2006
- Effects of inactivity on myosin heavy chain composition and size of rat soleus fibersMuscle & Nerve, 1998
- Influence of Spaceflight on Succinate Dehydrogenase Activity and Soma Size of Rat Ventral Horn NeuronsCells Tissues Organs, 1996
- Relationship between soma diameter and oxidative enzyme activity of α-motoneuronsBrain Research, 1992
- Effect of endurance training on the oxidative enzyme activity of soleus motoneurons in ratsActa Physiologica Scandinavica, 1991
- Marked and variable inhibition by chemical fixation of cytochrome oxidase and succinate dehydrogenase in single motoneurons.Journal of Histochemistry & Cytochemistry, 1989
- A new model for the growth of silicon dioxide layersJournal of Applied Physics, 1984
- Ventral motor neuron alterations in rat spinal cord after chronic exerciseCellular and Molecular Life Sciences, 1977
- Effects of physical training on the histochemistry and morphology of ventral motor neuronsExperimental Neurology, 1975
- Function and structure in the chronically isolated lumbo-sacral spinal cord of the dogJournal of Comparative Neurology, 1937