[CHANGES OF SPINAL MOTOR NEURONS IN MICE AFTER А SPACE FLIGHT]

The expression of choline acetyltransferase (ChAT), neurofilament (NF) protein 200 kDa, calbindin (CAB) 28 kDa, neuronal NO-synthase (nNOS), caspase 3, Ki-67 was studied in motor neurons from TIII–TV segments of the spinal cord in C57/ BL6 male mice by immunohistochemical methods 12 h after a 30 days-long space flight on the Bion-M1 biosatellite. Mice living under standard vivarium conditions served as a control. The motoneurons of experimental animals demonstrated the reactive changes that were manifested by the increase of their size, decrease in the number of subpopulations expressing ChAT and NF, increase of subpopulations containing CAB, appearance of motor neurons expressing nNOS, caspase-3, and the absence of Ki-67. The lack of proliferating gliocytes, the preservation of nucleolar component indicate the absence of necrobiotic changes characteristic of necrosis. The cytoplasmic vacuolization was observed in thionine-stained CAB-immunoreactive neurons. The disintegration of motor neurons into fragments resembling the apoptotic bodies was observed in single cells that contained caspase-3.