[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.

[Neuromuscular synaptic transmission at different stages of postnatal development in rats].

On the nerve-muscle preparation of rats diaphragm muscle on different stages of postnatal development, the comparison of morphological features and functions of synaptic apparatus, including induced secretion time parameters was carried out. It was found that, along with the reduced, compared to the adult animals, area of nerve endings in the newborn the speed of the motor nerve excitation was slower, intensity of spontaneous and induced secretion of quantum fluctuations was reduced and real synaptic delays in the end plate were intense. Severe degree of acetylcholine quanta asynchronous secretion with longer open state of the ion channel in newborns synapses can compensate reduction in reliability of synaptic transmission due to a decrease of the quantal content of the postsynaptic response.

[Myelination disorders in mechanism of hypogravity motor syndrome development].

When modeling effects of hypogravitation by the method of hindlimb unloading in rats the area of cross-section in lumbar part of a spinal cord was found to reduce. The analysis of spinal cord slides showed that these changes are associated with a decrease in the area of white substance of a spinal cord. Data obtained are consistent with our previous observation of a decrease in expression of the genes encoding myelin proteins.

[Excitatory action of GABA in ontogenesis].

GABA (gamma-aminobutyric acid) is the main inhibitory mediator in central nervous system. However, at early stages of ontogenesis, GABA has an excitatory effect on immature neurons. This review surveys modern concepts of the mechanisms of GABAergic excitation and physiological role of excitatory GABA in generation of patterns of network activity in developing brain.