Morphological changes in motoneurons of the oculomotor nucleus of mice after a 30-day space flight and through a 7-day period of readaptation to earth gravity.

The cellular mechanisms of neuroplastic changes in the structure of motoneurons and neuropils of the oculomotor (III) nuclei in mice after a 30-day space flight and 7 days after landing were studied. The results showed that microgravity caused degenerative phenomena in neurons: a decrease in the number of terminal dendritic branches was found both after flight and after readaptation to Earth's gravity. In mice after the flight, the number of axodendritic synapses was less than in the control, and their number was not restored after the readaptation.

Studying the structure of the nucleus of the trochlear nerve in mice through 7 days of readaptation to earth gravity after spaceflight.

The negative effect of hypogravity on the human organism is manifested to a greater extent after the astronauts return to the conditions of habitual gravity. In this work, to elucidate the causes underlying atypical nystagmus, arising after the flight, we studied structural changes in the motoneurons of the trochlear nerve after a 7-day readaptation of mice to the conditions of Earth's gravity. It is known, that motoneurons of the trochlear nerve innervate the muscle that controls the movement of the eyes in the vertical direction.

Influence of a 30-day spaceflight on the structure of motoneurons of the trochlear nerve nucleus in mice.

During spaceflight and immediately after it, adaptive neuroplastic changes occur in the sensorimotor structures of the central nervous system, which are associated with changes of mainly vestibular and visual signals. It is known that the movement of the eyeball in the vertical direction is carried out by muscles that are innervated by the trochlear nerve (CN IV) and the oculomotor nerve (CN III). To elucidate the cellular processes underlying the atypical vertical nystagmus that occurs under microgravity conditions, it seems necessary to study the state of these nuclei in animals in more detail after prolonged space flights.

Visual input controls the functional activity of goldfish Mauthner neuron through the reciprocal synaptic mechanism.

Goldfish are known to exhibit motor asymmetry due to functional asymmetry of their Mauthner neurons that induce the turns to the right or left during free swimming. It has been previously found that if the less active neuron is subjected to prolonged aimed visual stimulation via its ventral dendrite, the motor asymmetry of goldfish is inverted, testifying that this neuron becomes functionally dominant, while the size of the ventral dendrite under these conditions is reduced 2-3 times compared to its counterpart in mirror neuron. Earlier it has been also revealed that training optokinetic stimulation induces adaptation, a substantial resistance of both fish motor asymmetry and morphofunctional state of Mauthner neurons against prolonged optokinetic stimulation.

Role of different dendrites in the functional activity of the central neuron controlling goldfish behavior.

The structural mechanisms that control the neuronal functional activity maintaining the brain functional asymmetry were studied using the relationship between the function and structure of goldfish Mauthner neurons (MNs) responsible for fish motor asymmetry as a model. It was shown for the first time that the dominant activity in one of the two counter neurons symmetrically situated in the medulla oblongata directly correlates with changes in its integral volume and is inversely regulated by the size of its ventral dendrite. It is known that the variability of the neuron dimensions is due to changes in the actin component of the cytoskeleton.