The effects of exercise training of different intensities on neuromuscular junction morphology

Abstract

Little is known about the effects of exercise training on neuromuscular junction morphology in skeletal muscle. The objectives of this investigation were: 1) to determine if exercise training would elicit changes in neuromuscular junction morphology, 2) to determine if exercise training of different intensities would evoke specific changes in neuromuscular junction morphology, and 3) to determine whether changes in neuromuscular junction structure occur independently of changes in muscle fibre type and size. Twenty-four age and size matched male Sprague-Dawley rats were randomly assigned to three groups: high-intensity trained (HIT), low-intensity trained (LIT), or untrained. Neuromuscular junction morphology of the soleus muscle was determined via immunofluorescent staining. Presynaptic acetylcholine vesicles were visualized with SV-2 antibody in conjunction with fluorescein isothiocyanate labelled secondary secondary antibody. Postsynaptic acetylcholine receptors were identified with rhodamine labelled alpha-bungarotoxin. Laser scanning microscopy was used to produce images of synapses, which were used to quantitate the following: total area of SV-2 and alpha-bungarotoxin staining, density of acetylcholine vesicles and receptors, structural complexity, and synaptic coupling. To visualize nerve terminal branching, a smaller number of neuromuscular junctions were stained with C-2 antibody, which reacts with a neurofilament epitope, in conjunction with fluorescein isothiocyanate labelled secondary antibody. Total length of branching, number of branches, average length of branches, and ratio of secondary to primary branches per neuromuscular junction were determined. Citrate synthase activity, fibre type composition and fibre cross-sectional areas of the soleus muscle were assessed to determine the presence of a training effect in that muscle. Results indicate that training did induce hypertrophy of the neuromuscular junction that was independent of muscle hypertrophy. Although the HIT and LIT groups exhibited similar hypertrophic responses of the neuromuscular junction, the HIT group displayed more dispersed synapses than the LIT group. Neither exercise training program, however, resulted in altered densities of acetylcholine vesicles or receptors, nor did training significantly change synaptic coupling. Nerve terminal branching was also affected by exercise training. Neuromuscular junctions from the HIT group demonstrated a greater total length of branching, average length per branch, and number of finer, or secondary, branches than those of the LIT group.

Moderate aging does not modulate morphological responsiveness of the neuromuscular system to chronic overload in Fischer 344 rats

“…While even under normal conditions the mature NMJ displays constant, yet moderate remodeling (Wigston, 1989;Hill et al, 1991), alterations in neuromuscular activity, whether increased (exercise training) or decreased (paralysis), markedly exacerbate that remodeling (Brown and Ironton, 1977;Andonian and Fahim, 1988; Tsujimoto and Kuno, 1988;Deschenes et al, 1993). More recently, an interest in the capacity of aging to modulate activity related NMJ adaptability has been pursued.…”

“…NMJ adaptations to increased activity in the form of exercise training, i.e., treadmill running (Andonian and Fahim, 1988;Deschenes et al, 1993;Fahim, 1997).…”

“…Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NMJ adaptations to increased activity in the form of exercise training, i.e., treadmill running (Andonian and Fahim, 1988;Deschenes et al, 1993;Fahim, 1997). …”

Método Chordata combinado com eletroterapia na recuperação funcional após lesão do plexo braquial: relato de três casos clínicos

“…For instance, motor endplates are continuously remodeling in response to functional demands [9]. Therefore, stimulating the "muscle nerve interface" can prompt nerve growth, facilitating repair by the action of neurotrophins [10,11].…”

Age and activity-related changes in the respiratory motor system

“…5) 34) . In young rats, the training effects at neuromuscular junctions were introduced previously, such as an increased safety factor due to increased neurotransmitter release when given active training stimuli 35) , nerve terminal enlargement 36) , and increased acetylcholinesterase activity 37,38) . From these observations, it was thought that nerve terminal enlargement, increased acetylcholine release, and increased acetylcholinesterase activity were attributable to increased Fig.…”