Mosier DR, Siklos L, Gordon S, Booth FW.
Ann Neurol. 1998 Sep; 44: 458.
Morphological changes suggestive of denervation are present at neuromuscular junctions in atrophying muscle, both in space-flown animals (J Neuropathol Exp Neurol 1992;51: 415) and in rodent models of limb immobilization. However, whether these morphologic changes are associated with physiological alterations of motoneuron function is unknown. To begin to address this question, we examined spontaneous transmitter release at neuromuscular junctions of mice undergoing hindlimb unloading by tail suspension. In ICR mice undergoing tail suspension for 3 weeks (Am J Physiol 1988;254:C651), atrophy of 46% was observed in the soleus, a predominantly slow muscle, whereas only a 17% atrophy was observed in the plantaris, which is composed mostly of fast muscle fibers. Interestingly, miniature end-plate potential (MEPP) frequency did not differ between soleus muscle fibers of control and suspended mice. However, a two-fold increase in MEPP frequency was documented in plantaris muscle fibers following hindlimb unloading(p < 0.0005). These findings, which will be correlated with ongoing ultrastructural studies, represent the first evidence for physiological changes in motoneuron terminals during muscle unloading and could be relevant to processes influencing motor unit function in spaceflight and in disorders associated with muscle inactivity (eg, disuse atrophy, critical care neuromyopathies).
Publication Types:
Keywords:
- Animals
- Atrophy
- Hindlimb Suspension
- Mice
- Models, Biological
- Motor Neurons
- Muscle Denervation
- Muscle Fibers
- Muscle, Skeletal
- Muscles
- Muscular Atrophy
- Muscular Disorders, Atrophic
- Neuromuscular Junction
- Space Flight
- surgery
- NASA Discipline Musculoskeletal
- Non-NASA Center
Other ID:
UI: 102194971
From Meeting Abstracts