The neuromuscular junction on the top is from a young adult mouse; that on the bottom from an 2-year old mouse, which is quite old for a mouse. The postsynaptic neurotransmitter receptors are strained in red, the presynaptic neurotransmitter release apparatus in green and the axon in blue. In the young adult, the perfect apposition of pre- and postsynaptic structures is seen as yellow (red+green). In the old animal, the receptors are broken into small islands, some are no longer covered by nerves, and the axon is distended in some regions and atrophic in others. All of these age related changes are attenuated with caloric restriction or exercise, and some can even be reversed by one month of exercise begun when the animals are already old.
Calorie restriction and exercise attenuates aging
【LWBS 2015 05 18 A】(Pan Li edited from PNAS)
It is accepted that calorie restriction and exercise attenuates the process of aging. A research group from the United States has recently found that calorie restriction and exercise improves the structural abnormalities of the neuromuscular junction, the synapse between a motoneuron and a muscle fiber.
What is the neuromuscular junction?
The neuromuscular junction is a large synapse in the peripheral nervous system, and it is formed between a motoneuron and a muscle fiber. At the neuromuscular junction, the motoneuron axon controls the contraction of the muscle fiber it innervates. Neuromuscular junction is a specialized chemical synapse and in vertebrates, the neurotransmitter used is Acetylcholine (ACh).
The research group hypothesized that since calorie restriction and exercise appears to be the most effective anti-aging treatment, the beneficial effects on neural function of caloric restriction and exercise may be mediated by synapses. To test their hypothesis, they compared the structure of neuromuscular junction in young adult (1-3 mo-old) as well as aged (24-28 mo-old) mice, and found a variety of age-related structural alterations, including axonal swellings, sprouting, synaptic detachment, partial or complete withdrawal of axons from some postsynaptic sites, and fragmentation of the postsynaptic specialization in aged mice. Alterations were co-related to age, A life-long calorie-restricted diet significantly decreased the neuromuscular junction structural abnormalities in 24-mo-old mice. For Calorie restriction treatment, mice starting from 16 weeks after birth were fed with 60% the calories of the untreated littermates. Interestingly, one month of exercise (wheel running, 4km/d) in 22-mo-old mice also reduced age-related synaptic changes. These results demonstrate that aging affects the structure of the neuromuscular junction, while calorie restriction and exercise effectively attenuates the deterioration of the neuromuscular junction during aging.