|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1991 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1990 : ¥1,200,000 (Direct Cost : ¥1,200,000)
The role of the cerebellum in the cardiovascular control has been studied with ablation or stimulation experiments with anesthetized animals by various investigators. It is suggested that the vernal cortex and fastigial nucleus in the cerebellum are involved in the cardiovascular control. On the other hand, we have reported that the stimulation of three localized regions in cerebellar vernal cortex, medial regions of lobules I-III and VII-VIII, and the lateral region of lobules IX-X, caused a marked depression of the renal sympathetic nerve activity(RSNA)and systemic bloodpressure(BP)in anesthetized rabbits. Recently, we have also found that electrical stimulation of the lateral part of the lobules IX-X induces different responses from above on the cardiovascular functions(blood pressure, local blood flow and sympathetic nerve activity)both in anesthelized and decerebrated rabbits.
In the present study, in order to examine the mechanism of cerebellar cardiovascular control, RSNA and BP were measured in conscious rabbits at rest, during tilt and body movement. In the conscious state, as in the anesthetized state, cardiac- and respiratory-related rhythms were demonstrated in RSNA and BP at rest. A 300 head up tilt resulted in an initial decrease and a sustained increase of BP and an initial increase and a sustained decrease of RSNA. On the contrary, a 300 head down tilt caused an initial increase and a sustained decrease of BP and an initial decrease and a sustained increase of RSNA. The chronic destruction of cerebellar cortex of lobules IX-X, which was performed 5-7 days before the experiment, caused the fluctuations of BP and RSNA at rest. A 300 head up and down tilt resulted in an increase of BP and RSNA and also caused the significant fluctuations of BP and RSNA. These results indicate that the cardiovascular control region in the cerebellar vernal cortex plays a significant role in cardiovascular control during tilt in conscious rabbits.