Vasomotion in cerebral microcirculation of awake rabbits.

Cerebral arterioles of unanesthetized rabbits equipped with chronically implanted cranial windows exhibited spontaneous rhythmic variation in vessel caliber characteristic of vasomotion. This variation was noted in all examined vessels. The vasomotion was independent of arterial blood pressure or respiration. The average frequency was 0.74 cycles/min and was independent of vessel size. The mean amplitude of the oscillations had a statistically significant inverse relationship to vessel diameter (r = 0.69). Vasodilation induced by arterial hypercapnia, topical adenosine, or topical acetylcholine had no significant effect on the frequency or amplitude of vasomotion. Anesthesia significantly reduced the frequency in arterioles of all sizes and markedly reduced amplitude in large arterioles. Topical verapamil resulted in a statistically significant reduction in frequency and in peak amplitude. Variations in vessel diameter occurred simultaneously in arterioles and their companion venules. We conclude that the cerebral microcirculation displays active vasomotion, which is significantly depressed by anesthesia or topical verapamil. The results also suggest that vasomotion is probably controlled by local factors.