Changes in contractile properties of motor units of the rat medial gastrocnemius muscle after spinal cord transection. 2006

Jan Celichowski, and Włodzimierz Mrówczyński, and Piotr Krutki, and Teresa Górska, and Henryk Majczyński, and Urszula Sławińska
Department of Neurobiology, University School of Physical Education, 60-352 Pozñan, Poland. celichowski@awf.poznan.pl

The effects of complete transection of the spinal cord at the level of Th9/10 on contractile properties of the motor units (MUs) in the rat medial gastrocnemius (MG) muscle were investigated. Our results indicate that 1 month after injury the contraction time (time-to-peak) and half-relaxation time were prolonged and the maximal tetanic force in most of the MUs in the MG muscle of spinal rats was reduced. The resistance to fatigue also decreased in most of the MUs in the MG of spinal animals. Moreover, the post-tetanic potentiation of twitches in MUs diminished after spinal cord transection. Criteria for the division of MUs into three types, namely slow (S), fast fatigue resistant (FR) and fast fatigable (FF), applied in intact animals, could not be directly used in spinal animals owing to changes in contractile properties of MUs. The 'sag' phenomenon observed in unfused tetani of fast units in intact animals essentially disappeared in spinal rats and it was only detected in few units, at low frequencies of stimulation only. Therefore, the MUs in spinal rats were classified as fast or slow on the basis of an adjusted borderline of 20 ms, instead of 18 ms as in intact animals, owing to a slightly longer contraction time of those fast motor units with the 'sag'. We conclude that all basic contractile properties of rat motor units in the medial gastrocnemius muscle are significantly changed 1 month after complete spinal cord transection, with the majority of motor units being more fatigable and slower than those of intact rats.

UI MeSH Term Description Entries
D009046 Motor Neurons Neurons which activate MUSCLE CELLS. Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009119 Muscle Contraction A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments. Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D005260 Female Females
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013119 Spinal Cord Injuries Penetrating and non-penetrating injuries to the spinal cord resulting from traumatic external forces (e.g., WOUNDS, GUNSHOT; WHIPLASH INJURIES; etc.). Myelopathy, Traumatic,Injuries, Spinal Cord,Post-Traumatic Myelopathy,Spinal Cord Contusion,Spinal Cord Laceration,Spinal Cord Transection,Spinal Cord Trauma,Contusion, Spinal Cord,Contusions, Spinal Cord,Cord Contusion, Spinal,Cord Contusions, Spinal,Cord Injuries, Spinal,Cord Injury, Spinal,Cord Laceration, Spinal,Cord Lacerations, Spinal,Cord Transection, Spinal,Cord Transections, Spinal,Cord Trauma, Spinal,Cord Traumas, Spinal,Injury, Spinal Cord,Laceration, Spinal Cord,Lacerations, Spinal Cord,Myelopathies, Post-Traumatic,Myelopathies, Traumatic,Myelopathy, Post-Traumatic,Post Traumatic Myelopathy,Post-Traumatic Myelopathies,Spinal Cord Contusions,Spinal Cord Injury,Spinal Cord Lacerations,Spinal Cord Transections,Spinal Cord Traumas,Transection, Spinal Cord,Transections, Spinal Cord,Trauma, Spinal Cord,Traumas, Spinal Cord,Traumatic Myelopathies,Traumatic Myelopathy
D013904 Thoracic Vertebrae A group of twelve VERTEBRAE connected to the ribs that support the upper trunk region. Vertebrae, Thoracic
D013997 Time Factors Elements of limited time intervals, contributing to particular results or situations. Time Series,Factor, Time,Time Factor
D017208 Rats, Wistar A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain. Wistar Rat,Rat, Wistar,Wistar Rats
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus
D018482 Muscle, Skeletal A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Anterior Tibial Muscle,Gastrocnemius Muscle,Muscle, Voluntary,Plantaris Muscle,Skeletal Muscle,Soleus Muscle,Muscle, Anterior Tibial,Muscle, Gastrocnemius,Muscle, Plantaris,Muscle, Soleus,Muscles, Skeletal,Muscles, Voluntary,Skeletal Muscles,Tibial Muscle, Anterior,Voluntary Muscle,Voluntary Muscles

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