Influence of hindlimb unloading on the modulation of neurotransmitter secretion through the autoreceptor system

Corticospinal excitability after 5-day Dry Immersion in women

“…Due to the changes in the cytoskeleton, muscle fibers become less sensitive to calcium, and their contractility decreases (Shenkman and Kozlovskaya, 2019 ). In animal experiments, it was shown that support withdrawal results in a decrease in the postsynaptic membrane surface area covered with acetylcholine receptors, as well as a decrease in the number of receptors on the “fast” muscles' nerve endings (Tyapkina et al, 2006 ). Although the increase in spinal MEP latencies was not significant, and we do not know how pronounced the described molecular changes are after 5 days of DI, it is worth considering the possibility of these mechanisms affecting the evoked muscle responses.…”

“…Changes in brain volume, microstructure, and connectivity were observed after SF (Koppelmans et al, 2016;Jillings et al, 2020) and head-down tilt bed rest (Koppelmans et al, 2017;Lee et al, 2021), and the increase in excitability of motor responses was noted during support withdrawal (Zakirova et al, 2015) and parabolic flight (Davey et al, 2004;Badran et al, 2020). At the molecular level, changes in neuromuscular junctions, such as a decline in the postsynaptic excitatory potential amplitudes, a change in the enzyme activity, and a shift in the level of the ion equilibrium potentials, were reported in both animal (Tyapkina et al, 2006;Chibalin et al, 2018;Vilchinskaya et al, 2018) and human studies (Shenkman et al, 2017;Shenkman, 2020).…”