Cerebral cortical blood flow during loss of consciousness induced by gravitational stress in rhesus monkeys

Abstract

We investigated the influence of +G z acceleration (head-to-foot inertial forces) onset on cerebral cortical blood flow (CBF) of rhesus monkeys to study the mechanisms underlying +G z-induced loss of consciousness (G-LOC). CBF was measured through a chronic cranial window by laser-Doppler flowmetry and electrodes in contact with the dura mater were used to detect G-LOC (suppression of the cortical electrical activity). The animals were centrifuged up to +12 G z with different G-onset rate until G-LOC occurred. G-LOC was preceded by a 2–5 s decrease in CBF. At G-LOC detection, CBF was not related to G-onset rate (mean CBF change: −76±9% of control value). We conclude that G-LOC results from cerebral ischemia rather than from mechanical stresses applied to the brain.