Leukocyte involvement in vasomotor reactivity of the cerebral vasculature.

A ctivation of leukocytes may play a part in the / \ complex pathophysiological cascade leading to A.V. vasomotor reaction in cerebral arteries. In this issue of Stroke, Akopov et al report changes in endothelium-dependent relaxation by intravascular chemical leukocyte activation involving the cerebral circulation. This interesting study highlights a potential role for leukocytes in the modulation of vasomotor reactivity of large cerebral arteries. Large cerebral arteries, including the middle cerebral artery (MCA), are already well known for their marked reactivity, even hyperreactivity, which is best demonstrated in the vasospasm associated with subarachnoid hemorrhage. The potential effects of leukocyte-vascular interactions on vasoregulation can be seen in the larger context of cerebral ischemia and its initiation of the mechanisms of so-called reperfusion injury, the "no-reflow" phenomenon, endothelial cell damage (initiated by oxygen free radicals, porymorphonuclear [PMN] leukocyte adherence, transmigration, and phagocytosis), and vascular smooth muscle responses.