Increased and decreased activity elicits specific morphological adaptations of the neuromuscular junction

Deschenes, Michael R.; Tenny, Kelly; Wilson, Meredith H.

doi:10.1016/j.neuroscience.2005.10.042

Cited by 61 publications

(41 citation statements)

References 29 publications

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“…Similar positive effects of exercise on skeletal neuromuscular function in the elderly have been reported, although the underlying mechanism(s) are not clear [68–70]. Muscle activity has been shown to enhance the expression of muscle-derived neurotrophins at the neuromuscular junction [71, 72], alter the regulation of central serotonergic activity [73], and increase nerve terminal branching at the neuromuscular junction [74]. Exercise can enhance the expression of anti-apoptotic markers in aging muscle (for a review, see [75]).…”

Section: Discussionmentioning

confidence: 93%

The Effects of Aging on Hypoglossal Motoneurons in Rats

et al. 2008

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Aging can result in a loss of neuronal cell bodies and a decrease in neuronal size in some regions of the brain and spinal cord. Motoneuron loss in the spinal cord is thought to contribute to the progressive decline in muscle mass and strength that occurs with age (sarcopenia). Swallowing disorders represent a large clinical problem in elderly persons; however, age-related alterations in cranial motoneurons that innervate muscles involved in swallowing have been understudied. We aimed to determine if age-related alterations occurred in the hypoglossal nucleus in the brainstem. If present, these changes might help explain alterations at the neuromuscular junction and changes in the contractile properties of tongue muscle that have been reported in older rats. We hypothesized that with increasing age, there would be a loss of motoneurons and a reduction in neuronal size and the number of primary dendrites associated with each hypoglossal motoneuron. Neurons in the hypoglossal nucleus were visualized with the neuronal marker NeuN in young (9–10 months), middle-aged (24–25 months), and old (32–33 months) male F344/BN rats. Hypoglossal motoneurons were retrograde labeled with injections of Cholera Toxin β into the genioglossus muscle of the tongue and visualized using immunocytochemistry. Results indicated that the number of primary dendrites of hypoglossal motoneurons decreased significantly with age, while no age-associated changes were found in the number or size of hypoglossal motoneurons. Loss of primary dendrites could reduce the number of synaptic inputs and thereby impair function.

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Section: Discussionmentioning

confidence: 93%

The Effects of Aging on Hypoglossal Motoneurons in Rats

et al. 2008

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“…The average total area of endplate staining in the EDL muscle of exercised animals was significantly decreased (918.5 ± 36.8 μm 2 ) as compared to endplates of sedentary control animals (1095.9 ± 30.3 μm 2 ; Figure 3a). The dispersion of AChRs was measured by dividing the stained area by the total area of the endplates and multiplying by 100 (Deschenes et al, 2006). There was no difference in the percent dispersion of control and exercised EDL endplates, (71.0% ± 3.1% and 76.6% ± 3.5%, respectively).…”

Section: Resultsmentioning

confidence: 99%

“…Ten representative endplates in the horizontal plane were selected from each muscle to determine endplate area. Total area of the endplate perimeter was measured which included stained receptor clusters along with non-stained regions interspersed within those clusters (Deschenes et al, 2006). The endplate areas were calculated using the Zeiss LSM 5 Image Examiner program.…”

Section: Methodsmentioning

confidence: 99%

Glial cell line-derived neurotrophic factor protein content in rat skeletal muscle is altered by increased physical activity in vivo and in vitro

et al. 2011

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Current evidence suggests that exercise and glial cell line-derived neurotrophic factor (GDNF) independently cause significant morphological changes in the neuromuscular system. The aim of the current study was to determine if increased physical activity regulates GDNF protein content in rat skeletal muscle. Extensor Digitorum Longus (EDL) and Soleus (SOL) hindlimb skeletal muscles were analyzed following 2 weeks of involuntary exercise and 4 hours of field stimulation or stretch in muscle bath preparations. GDNF protein content was measured via ELISA. Two weeks of exercise increased GDNF protein content in SOL as compared to sedentary controls (4.4 ±0.3 pg GDNF/mg tissue and 3.1 ±0.6 pg GDNF/mg tissue, respectively) and decreased GDNF protein content in EDL as compared to controls (1.0 ±0.1 pg GDNF/mg tissue and 2.3 ±0.7 pg GDNF/mg tissue, respectively). GDNF protein content in the EDL decreased following both field stimulation (56% ±18% decrease from controls) and stretch (66% ±10% decrease from controls). SOL responded to field stimulation with a 38% ±7% increase from controls in GDNF protein content, but showed no change following stretch. Pre-treatment with α-bungarotoxin abolished the effects of field stimulation in both muscles and blocked the effect of stretch in EDL. α-bungarotoxin pre-treatment and stretch increased GDNF protein content to 240% ±10% of controls in the SOL. Exposure to carbamylcholine decreased GDNF protein content to 51% ±28% of controls in the EDL but not SOL. These results suggest that GDNF protein content in skeletal muscle may be controlled by stretch, where it may increase GDNF protein content, and membrane depolarization/ACh which acts to decrease GDNF protein content. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. 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. Keywords NIH Public Access Author ManuscriptNeuroscience. Author manuscript; available in PMC 2012 February 3.Published in final edited form as: Neuroscience. 2011 February 3; 174: 234-244. doi:10.1016/j.neuroscience.2010. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript Effect of exercise on the peripheral nervous systemIncreased physical activity has been shown to alter the structure and function of the neuromuscular junction (NMJ). Exercise increases the size and degree of branching of motor nerve terminals at the NMJ (Andonian and Fahim, 1987), increases total area of both preand postsynaptic elements (Deschenes et al., 1993), and increases quantal content of acetylcholine (ACh) release (Dorlochter et al., 1991). The dispersion of acetylcholine receptors (AChRs), including both endplate peri...

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“…In young adult rats, 10 weeks of treadmill training produced an increase the size of the nerve terminal at the motor endplate [17]. The same study showed that 10 weeks of an intervention to reduce muscle usage (suspending the hindlimbs) resulted in a reduction in postsynaptic AChR area, associated with muscle fiber atrophy.…”

Section: Introductionmentioning

confidence: 85%

Sequence of Age-Associated Changes to the Mouse Neuromuscular Junction and the Protective Effects of Voluntary Exercise

et al. 2013

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Loss of connections between motor neurons and skeletal muscle fibers contribute to motor impairment in old age, but the sequence of age-associated changes that precede loss of the neuromuscular synapse remains uncertain. Here we determine changes in the size of neuromuscular synapses within the tibialis anterior muscle across the life span of C57BL/6J mice. Immunofluorescence, confocal microscopy and morphometry were used to measure the area occupied by nerve terminal synaptophysin staining and postsynaptic acetylcholine receptors at motor endplates of 2, 14, 19, 22, 25 and 28month old mice. The key findings were: 1) At middle age (14-months) endplate acetylcholine receptors occupied 238±11 µm2 and nerve terminal synaptophysin 168±14 µm2 (mean ± SEM). 2) Between 14-months and 19-months (onset of old age) the area occupied by postsynaptic acetylcholine receptors declined 30%. At many endplates the large acetylcholine receptor plaque became fragmented into multiple smaller acetylcholine receptor clusters. 3) Between 19- and 25-months, the fraction of endplate acetylcholine receptors covered by synaptophysin fell 21%. By 28-months, half of the endplates imaged retained ≤50 µm2 area of synaptophysin staining. 4) Within aged muscles, the degree to which an endplate remained covered by synaptophysin did not depend upon the total area of acetylcholine receptors, nor upon the number of discrete receptor clusters. 5) Voluntary wheel-running exercise, beginning late in middle-age, prevented much of the age-associated loss of nerve terminal synaptophysin. In summary, a decline in the area of endplate acetylcholine receptor clusters at the onset of old age was followed by loss of nerve terminal synaptophysin from the endplate. Voluntary running exercise, begun late in middle age, substantially inhibited the loss of nerve terminal from aging motor endplates.

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Increased and decreased activity elicits specific morphological adaptations of the neuromuscular junction

Cited by 61 publications

References 29 publications

The Effects of Aging on Hypoglossal Motoneurons in Rats

The Effects of Aging on Hypoglossal Motoneurons in Rats

Glial cell line-derived neurotrophic factor protein content in rat skeletal muscle is altered by increased physical activity in vivo and in vitro

Sequence of Age-Associated Changes to the Mouse Neuromuscular Junction and the Protective Effects of Voluntary Exercise

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