Roles of the vestibular system in controlling arterial pressure in conscious rats during a short period of microgravity.

In order to evaluate the roles of the vestibular system in controlling arterial pressure (AP) during exposure to a short period of microgravity (microG), the AP was measured in conscious free-moving rats having intact vestibular systems and those having vestibular lesions (FM-Intact and FM-VL groups, respectively). During free drop-induced microG, the AP increased in the FM-Intact group; it was 38+/-4 mmHg more than the AP observed during 1G. However, the increase in AP was significantly lower in the FM-VL group (20+/-2 mmHg). Further, to examine the sudden effect of a body floating in the midair in response to the AP during exposure to muG a body stabilizer was placed on the back of rats having intact vestibular systems and those having vestibular lesions (STAB-Intact and STAB-VL groups, respectively). The increase in the AP was significantly depressed in the STAB-Intact group; when compared with that in the FM-Intact group, but the increase was still significant (27+/-2 mmHg). On the other hand, the increase in the AP was completely eliminated in the STAB-VL group (7+/-5 mmHg). These results indicate that the AP increases during exposure to muG in conscious rats, and the vestibular system and body stability are significantly involved in this response.