Effects of microgravity elicited by parabolic flight on abdominal aortic pressure and heart rate in rats

Abstract

Abdominal aortic pressure (AAP), heart rate (HR), and aortic nerve activity (ANA) during parabolic flight were measured by using a telemetry system to clarify the acute effect of microgravity (μG) on hemodynamics in rats. While the animals were conscious, AAP increased up to 119 ± 3 mmHg on exposure to μG compared with the value at 1 G (95 ± 3 mmHg; P < 0.001), whereas AAP decreased immediately on exposure to μG under urethane anesthesia (μG: 72 ± 9 mmHg vs. 1 G: 78 ± 8 mmHg; P < 0.05). HR also increased during μG in conscious animals (μG: 349 ± 12 beats/min vs. 1 G: 324+9 beats/min; P < 0.01), although no change was observed under anesthesia. ANA, which was measured under anesthesia, decreased in response to acute μG exposure (μG: 33 ± 7 counts/s vs. 1 G: 49 ± 5 counts/s; P < 0.01). These results suggest that μG essentially induces a decrease of arterial pressure; however, emotional stress and body movements affect the responses of arterial pressure and HR during exposure to acute μG.