Abstract
The internal diameter (10) of small arteries, which play an important role as resistance vessels, is controlled by the sympathetic nervous system. We studied effects of cervical sympathetic nerve section, electrical stimulation of this nerve and a-receptor blockade (phentolamine, iv) on 10 of central artery (CA) and marginal artery (MA) of the rabbit ear. Serial measurements of ID’s of CA and MA were made on angiograms of 13 anesthetized rabbits in a length of about 150 and 120 mm, respectively. Under the control condition, i.e., sympathetic nerve was intact, 10 tapered steeply at the proximal portion of both arteries. With sympathetic nerve section, all sites of CA and MA were dilated above the control level. Particularly, 10 increased significantly about 4 times in CA at 50 mm and 3 times in MA at 40 mm from the bifurcation of both arteries. with 2 Hz electrical stimulation of the peripheral cut end of sympathetic nerve, CA and MA constricted nearly to the control levels in almost entire length. The relative magnitude of vasoconstriction was larger in CA than MA. When α-receptor blockade was administered following the sympathetic nerve section, further dilatation of 10 occurred in all sites of CA. This dilatation by α-receptor blockade was significantly dominant in the distal half of CA. From above results, we concluded that the sympathetic and humoral control in ID is nonuniform not only between CA and MA but also within each of these small arteries in the rabbit ear.
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