Abstract
Vestibular and somatosensory systems are known as graviceptors. However, relationship between these sensors and circulatory systems has been unclear. In the study, we measured arterial pressure (AP) during 1G and microgravity condition induced by free drop. Conscious rats (n = 56) were divided into four groups, i.e., Intact, sino-aortic denervation (SAD) and vestibular lesion (VL), and SAD+VL. All groups were exposed to microgravity with and without body stabilizer (FLOAT and STAB, respectively), which is a septum in a cage to avoid body float or change in somatosensory input, without restriction during microgravity. With exposure to microgravity, AP in the FLOAT Intact rats raised 37± mmHg, compared to 1G condition, but the rise was depressed to 20± 2 mmHg in FLOAT VL rats. These changes were not seen in anesthetized rats. Moreover, the change significantly decreased in STAB rats (28 ± 3 and 7 ±5 mmHg for Intact and VL rats, respectively). No significant differences were observed between Intact and SAD rats, and between VL and SAD+VL rats. Arrhythmia, such as bigemia was observed in all FLOAT Intact rats, but the appearance rate was significantly decreased in FLOAT VL and STAB Intact rats. These results indicate that vestibular and somatosensory systems are playing important roles for controlling AP and heart rate during exposure to microgravity in conscious state. [Jpn J Physiol 55 Suppl:S226 (2005)]
