[Effect of space flight and head-down position on motoneuron- glia-capillary system of the rat bone marrow]

In the anterior horns of the rats exposed to a 14 day space mission and 8-11 hrs of earth gravity environments postflight there occurred morphologic changes pointing to the motoneuron hypofunction which was expressed to a greater extent in motoneurons at C3-C4 level than at L4-L5 level. As the time of the rat stay under Earth gravity conditions following 14-day space mission is increased up to 48-51 hrs the structural changes in the motoneuron-glia capillary system at the L4-L5 level is indicative of an activation of spinal cord motoneurons. The 14 day head-down suspension (HDS) of the rats results in the morphologic changes in anterior horns which are an indication of hyperfunction of motoneurons in cervical enlargement and hypofunction of motoneurons in lumbar enlargement of the spinal cord. An increase of HDS time up to 32 days intensifies the morphologic changes in lumbar enlargement motoneurons. A lesser extent of morphologic changes manifestation in the motoneuron-glia-capillary system at L4-L5 level in the rats following a 14-day HDS as compared to the rats exposed to 14-day space mission is indicative of more slower development of motoneuron hypofunction under Earth gravity conditions as opposed to space environments.