Regional Differences in the Regulation of Contraction-Relaxation Machinery of Vascular Smooth Muscle

Abstract

It is well-established that there are marked differences in the basal tone and reactivity to various vasoactive agents of the cerebral and mesenteric arterial vascular beds. While cerebral arteries have considerable, mesenteric arteries have negligible basal tone. It seems likely that the metabolic factors are the most important controllers of cerebral circulation, but they seem far less important in regulating intestinal blood flow. Furthermore, the neural control is probably much more pronounced in the intestinal than in the cerebral circulation. These differences urged us to compare the effects of various contractile and dilatory agents on similar sizes of middle cerebral and mesenteric arteries of the cat. To induce contraction we used potassium ions as well as various agonists of vascular smooth muscle calcium mobilizing receptors. Relaxation of the vascular smooth muscle was achieved by drugs acting via the endothelium (acetylcholine, adenosine triphosphate) and directly on the smooth muscle (adenosine) (Furchgott, 1983).