[The role of spinal motoneurons in the mechanisms of hypogravitational motor syndrome development].

Studies results of gravity unloading influence on spinal control system of muscle structure and functions are summarized. It was shown that demyelization of axons due to reduction of genes expression responsible for myelin proteins synthesis, decrease in one of the key enzymes of cholinergic system--cholineacetyltransferase activity, alteration of normal kinetics of quantal and non-quantal neurotransmitter secretion, impaired autoregulation of acetylcholine secretion from motor nerve endings through presynaptic cholinergic receptors, slowing of axonal transport of substances in motor neurons that innervate postural muscles played the important role in the development of hypogravitational motor symptoms. At the same time, the evidences of neuroprotective mechanisms enclosing (increase in heat shock proteins Hsp25 and Hsp70 expression), that hinder apoptosis development in motor neurons and glial cells in the spinal cord under conditions of model hypogravity, were revealed.