Abstract
Six rabbits with transparent chambers introduced into the ears according to the Sandison 1 technique were studied. The blood vessels studied included both preformed, and newly formed ones of from 10 days to 4 months old. The reaction to ephedrine of these various types of vessels was essentially the same.
Ephedrine hydrochloride in 0.1% to 1.0% solutions in 0.9% saline was introduced by intravenous injection into the marginal vein of the unobserved ear or the saphenous vein of the leg and continuous observation with the microscope under low power was made during the first half hour after the injection.
Ephedrine in doses from 0.1 to 0.8 mg. (0.1% solution) injected into the blood stream did not produce a change in the vessels of the ear chamber. A slight narrowing of the central artery and a slowing of the circulation in the vascular bed was observed when the amount injected was 1 mg. (1% solution). The flow in a few capillaries became reversed, while in a few others it was accelerated, although the calibre of these showed no changes. The effect took place in a half to one minute after the injection and disappeared in about 5 minutes.
With a dose of 2 mg. (1% solution) the constriction of the central artery was more marked. The wave of constriction started from the central portion and travelled toward the periphery. This appears to differ from the effect exerted by epinephrin, which usually produced a wave starting from the opposite direction, namely from the periphery to the center. The arterioles, venules and capillaries again showed no changes in the size of the lumen. A slowing or reversal of the flow in a number of these minute vessels was apparently secondary to the changes in the arteries.
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