Modification of motoneuron size after partial denervation in neonatal rats.
Our previous studies have shown that partial denervation of extensor digitorum longus muscle (EDL) in the rat at 3 days of age causes an increase in the activity of the intact motoneurons. The originally phasic pattern of activity of EDL became tonic after partial denervation. These modifications of motoneuron activity were associated with the change in the phenotype of the muscle from fast to slow contracting and with a conversion of the muscle fibres from a fast to a slow type. The present study investigates whether the size of the cell body of the active EDL motoneurons change in parallel with the altered muscular activity. The study involved partial denervation of rat EDL muscle by section of the L4 spinal nerve at 3 days of age. Then the remaining motoneurons from L5 spinal nerve supplying the EDL muscle were retrogradly labelled with horseradish peroxidase two months later. The results show a reduction in motoneuron size in parallel with an increase in activity of the motoneurons after partial denervation of EDL muscle.
Tyc
F
F
Laboratoire Plasticité et Physio-Pathologie de la Motricité, UMR 6196, CNRS, Marseille cedex, France. tycfr@free.fr
Vrbová
G
G
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology; D019771:Axotomy; D016764:Cell Polarity / Q000502:physiology; D048430:Cell Shape / Q000502:physiology; D048429:Cell Size; D004396:Coloring Agents; D003714:Denervation / Q000009:adverse effects; D004195:Disease Models, Animal; D006735:Horseradish Peroxidase; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000294:innervation* / Q000378:metabolism; D059348:Peripheral Nerve Injuries; D010525:Peripheral Nerves / Q000503:physiopathology; D010641:Phenotype; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D004396:Coloring Agents; D006735:Horseradish Peroxidase