Effects of intermittent 45¡ã headª²up tilt on compliance of jugular vein and mesenteric vein in rabbits after simulated weightlessness

    SUN Huiª²Pin, SUN Xiª²Qing, WANG Bing, YAO Yongª²Jie, GENG Jie, SHI Fei

    Department of Aerospace Biodynamics, School of Aerospace Medicine, Fourth Military Medical University, Xi¬ðan 710033, China

    ¡¾Abstract¡¿ AIM: To observe the effects of simulated weightlessness and intermittent headª²upª²tilt 45¡ã on the compliance of jugular and mesenteric vein in rabbits. METHODS: Twentyª²four healthy male rabbits were randomly divided into three groups: control group, simulated weightlessness group and countermeasure group, with 8 rabbits in each group. Simulated weightlessness group kept headª²down tilt for 21 d. The countermeasure group kept headª²up tilt 2 h every day during the 21 d headª²down tilt. After 21 d experiment, the compressionª²displacement relationship of jugular and mesenteric vein strips and rings was observed. RESULTS: With the same compression, the displacement of jugular vein in the simulated weightlessness group decreased significantly compared with that in control group (P<0.05 or P<0.01) and the displacement of mesenteric vein in simulated weightlessness group increased significantly compared with that control group (P<0.05). With the same compression, the displacement of both jugular vein and mesenteric vein in countermeasure group had no obvious difference from that of control group. With the same compression, the displacement of jugular vein in countermeasure group increased significantly compared with that in weightlessness group, but the displacement of mesenteric vein decreased significantly (P<0.05). CONCLUSION: A twentyª²oneª²day simulated weightlessness may lead to a significant decrease of jugular venous compliance and an increase of mesenteric venous compliance in rabbits. Training of 45¡ã headª²up tilt 2 h per day can counteract the effects of simulated weightless on the mesenteric and jugular venous compliance. ......