In a reported series1 of experiments on isolated iris dilator an observation was made that an antagonism existed between atropine and adrenergic drugs on the contracted strip. In other words, the isolated dilator of iris when contracted by a sympathetic or adrenergic drug relaxes to atropine just as the sphincter does when contracted by acetylcholine. This throws doubt on the idea that reactions to sympathetic and parasympathetic drugs predicate a corresponding innervation. Poos2 from his work on isolated iris muscles favored the idea of a double innervation of the sphincter. He found a depressing effect on the sympathetic side in addition to a contracting, stimulating, parasympathetic action but found no corresponding responses from the dilator, exposed to pilocarpine and choline. Velhagen,3 on the other hand, demonstrated an unexpected contraction of the dilator in response to acetylcholine, but he rejected the hypothesis of a double innervation of the
HEATH P, SACHS E. ANTAGONISM BETWEEN ADRENERGIC DRUGS AND ATROPINE IN THE ISOLATED IRIS DILATOR. Arch Ophthalmol. 1940;24(1):142–148. doi:10.1001/archopht.1940.00870010164014
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