Aging Induces Changes in the Somatic Nerve and Postsynaptic Component without Any Alterations in Skeletal Muscles Morphology and Capacity to Carry Load of Wistar Rats

Abstract

The present study aimed to analyze the morphology of the peripheral nerve, postsynaptic compartment, skeletal muscles and weight-bearing capacity of Wistar rats at specific ages. Twenty rats were divided into groups: 10 months-old (ADULT) and 24 months-old (OLD). After euthanasia, we prepared and analyzed the tibial nerve using transmission electron microscopy and the soleus and plantaris muscles for cytofluorescence and histochemistry. For the comparison of the results between groups we used dependent and independent Student's t-test with level of significance set at p ≤ 0.05. For the tibial nerve, the OLD group presented the following alterations compared to the ADULT group: larger area and diameter of both myelinated fibers and axons, smaller area occupied by myelinated and unmyelinated axons, lower numerical density of myelinated fibers, and fewer myelinated fibers with normal morphology. Both aged soleus and plantaris end-plate showed greater total perimeter, stained perimeter, total area and stained area compared to ADULT group (p < 0.05). Yet, aged soleus end-plate presented greater dispersion than ADULT samples (p < 0.05). For the morphology of soleus and plantaris muscles, density of the interstitial volume was greater in the OLD group (p < 0.05). No statistical difference was found between groups in the weight-bearing tests. The results of the present study demonstrated that the aging process induces changes in the peripheral nerve and postsynaptic compartment without any change in skeletal muscles and ability to carry load in Wistar rats.

Age-related changes and effects of regular low-intensity exercise on gait, balance, and oxidative biomarkers in the spinal cord of Wistar rats

“…Since SFI is very sensitive to lesion in this nerve (16), the decreased SFI found in 24- and 30-month-old rats in the present study indicates sciatic nerve lesion. In fact, morphological changes were found in peripheral nerves of 10- and 24-month-old Wistar rats (31).…”

Ladder-based resistance training with the progression of training load altered the tibial nerve ultrastructure and muscle fiber area without altering the morphology of the postsynaptic compartment

“…All outcomes analyzed in this study followed standardized criteria ( Carbone et al, 2017 ; Krause Neto et al, 2017 ; Bessaguet et al, 2018 ; Krause Neto et al, 2022b ). We took fifteen microphotographs per nerve per rodent in each group according to the protocol by Krause Neto et al (2022b) .…”

“…Recent work has suggested that the increase or absence of stimuli can elicit changes in the neuromuscular system ( Wilson and Deschenes, 2005 ; Krause Neto et al, 2017 ; Deschenes et al, 2021 ; Krause Neto et al, 2021 ; Deschenes and Stock, 2022 ; Krause Neto et. 2015 ).…”