[Functioning of the brain vessels in rats after repeated simulation of some effects of microgravity (histological...

Histological methods were employed to investigate brain vessels of rats subjected to 30-d tail-suspension and 30-d readaptation in the horizontal position afterwards, and suspended again for 14 days simultaneously with other rats that had no such experience in the past. Repeated suspension produced, although there was blood redistribution to the cranial end, much less profound changes in brain vessels as compared with the previous 30-d suspension and the first-time suspended mates. This suggests an unknown arterial mechanism triggered in the region forward of the extracerebral arteries of the brain surface which hampered an excess blood flow to the brain during repeated suspension.