Fig. 1

Representative original recordings of arterial pressure at the level of the brain (brain AP) of an intact rat exposed to +5.0 Gz acceleration without anti-G equipment. A Sprague–Dawley rat (350 g body weight) anesthetized with urethane (1.2 g kg⁻¹ body weight) was placed in a prone position on the flat table of the centrifuge (115-cm-long arm; see details in text). The front teeth of the rat were fastened to the centrifuge table using a string. An arterial catheter was connected to a pressure transducers (DX-360, Nihon Koden, Tokyo, Japan) placed at the level of the rat brain. A G value was determined using the length of the center-to-head position of the animal and revolution speed at the animal’s head. The ordinate axis of loaded Gz is expressed as a logarithmic scale. When the rat was exposed to +5.0 Gz (head-to-tail longitudinal G) for 15 s at an on-set rate of 0.004 G/s), brain AP was decreased to around a zero level. The mean values of seven rats were shown in the text [22, 25, 31–34]