Vasomotion of basilar arteries in vivo.

Vasomotion is a rhythmic change in vascular caliber that has been described in vivo mainly in peripheral arterioles. In this study, we have characterized vasomotion in a large artery of the brain in vivo. In anesthetized rats, spontaneous vasomotion was observed in 38 of 47 basilar arteries visualized through a cranial window. Base-line arterial diameter was 259 +/- 9 (means +/- SE) microns. Under control conditions, the frequency of vasomotion was 4.8 +/- 0.2 cycles/min, and the amplitude was 19 +/- 2% of the mean diameter. Vasomotion usually occurred simultaneously along the entire length of the vessel, but in some arteries it propagated in either direction. Moderate hypertension (phenylephrine) or vasoconstriction induced by topical application of serotonin, vasopressin, or the thromboxane analogue U 46619 increased the frequency of vasomotion. Moderate hypotension or vasodilation induced by nitroglycerin, adenosine, or acetylcholine decreased the frequency. Marked hypertension, hypotension, or vasodilatation abolished vasomotion. Thus vasomotion of the basilar artery in vivo 1) is common and of relatively large amplitude, 2) does not seem to be driven by a single pacemaker, and 3) is dependent on vessel diameter or vasomotor tone.