Fig. 5

Representative original recordings of brain-tissue blood flow (brain flow) of the cortex or the hippocampus of each rat exposed to +3.0 Gz acceleration for 15 s without anti-G equipment. Brain Flow was measured by the laser flowmeter (One Channel of Omega FLO-C1, Omega-Wave, Tokyo) with a glass-fiber flow probe inserted directly to the brain tissue of the cortex or the hippocampus. The loaded G is expressed as a logarithmic scale. Brain AP arterial pressure at a level of the brain, aECG amplified electrocardiogram, HR heart rate, CVP central venous pressure. Acceleration of +3.0 Gz for 15 s without anti-G equipment decreased cortex-tissue blood flow from 5.7 ± 1.9 to 4.3 ± 2.3 ml/min/100 g of tissue, that is 76 ± 9 % (n = 6; SE), and hippocampus-tissue blood flow from 19.6 ± 8.1 to 13.5 ± 6.6 ml/min/100 g of tissue, that is 69 ± 6 % (n = 7, SE). Although there was no significant difference in %-decrease in blood flow between the two brain tissues, the %-decreases in flow in ml/min/100 g of tissue of the hippocampus (6.1 ± 2.4) was significantly larger than that of the cortex (1.4 ± 0.7) [21, 28]