OBSERVATIONS ON THE EFFECT OF CERTAIN DRUGS ON THE SMALL BLOOD VESSELS OF THE RABBIT EAR BEFORE AND AFTER DENERVATION

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Abstract
A study of the reactions of the minute blood vessels seen in the transparent chambers inserted in the ears of albino rabbits was presented. The tissue grown into a transparent chamber inserted in the rabbit''s ear was entirely suitable for physiologic studies. The response to epinephrine was a consistent constriction of the arterioles accompanied by slight narrowing of the venules. Ephedrine, in general, produced the same response as epinephrine. There was evidence of refractoriness to repeated doses of ephedrine. Pitressin in the dose used (0.1 pressor unit/kg, of body wt.) had the most pronounced vasoconstrictor action. There was refractoriness to repeated doses. Ergotoxine blocked the vasoconstrictor action of epinephrine. Stimulation of the cervical sympathetic chain produced a constriction of the arterioles in the window more consistently than did stimulation of the dorsal or great auricular nerves. The denervated vessels in the chamber became hypersensitive to epinephrine and regained their "tone" after de-nervation. Suggestions were made as to the mechanism involved. The blocking action of ergotoxine and the phenomenon of tachyphylaxis are apparently somewhat altered by denervation.