Abstract
It has been well documented that muscle unloading elicits significant decrements in muscle strength and size. In contrast, the effects of muscle unloading on the neuromuscular junction (NMJ) are less elucidated and the potential of pre‐habilitative conditioning remains unknown. The aim of this study was to examine the impact of unloading on the NMJs of aged rats, as well as the capacity of pre‐habilitation to affect those synapses. Thirty aged (25 mo) male Fischer 344 rats were assigned to 3 groups; 1) control, 2) unloaded (UL), 3) pre‐habilitation before unloading (PH‐UL). UL rats were subjected to hindlimb suspension for 2 weeks, and PH‐UL rats completed a 2 week (5days/wk) treadmill running program before 2 weeks of hindlimb suspension. Following all interventions, all rats were euthanized and soleus muscles were removed and frozen at resting length. Cytofluorescent techniques were used to visualize pre‐synaptic nerve terminal branching, and post‐synaptic acetylcholine receptors. Confocal microscopy was used to collect images of pre‐ and post‐synaptic morphology. Our results indicated that neither pre‐ nor post‐synaptic morphological parameters were altered in UL or PH‐UL rats. Thus, a 2 week unloading period is insufficient to modify synaptic structure among aged rats. Moreover, the combination of 2 weeks of run training and 2 weeks of unloading also failed to provoke changes in NMJ morphology.Supported by the National Institute on Aging, and The Foundation for Aging Studies and Exercise Science Research.
Published Version
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