Ergonomics Miosis.

Abstract

In 1906 Dale 1 demonstrated constriction of the cat's iris by ergotoxine and attributed this to direct stimulation of the iris sphincter. Recently Koppanyi 2 reported that a sufficient concentration of ergotamine injected intraocularly paralyzes the motor sympathetic terminations in the dilatator pupillae and stated that the abolition of sympathetic tonus was sufficient basis for explanation of ergotoxine constriction.

Our results of numerous studies on the isolated sphincter muscle of the iris in an oxygenated Locke-Ringer bath warrant the support of Dale's conclusion that ergotoxine constricts this muscle to a considerable degree. Ergotamine tartrate produces the same effect as ergotoxine. However, the results do not support the conclusions of Zunz, 3 Hess 4 and Poos 5 that ergotoxine causes this increased tonus by the parasympathetic route. Atropine in considerable concentration fails to “break through” the tonus elicited by ergotoxine and it does not prevent this tonus increase if applied before ergotoxine (Fig. 1).

In the intact eye of 7 cats, after recovery from light ether, ergotoxine miosis, produced by Koppanyi's intraocular method, was partially lessened by atropine intraocularly. The pupil of the eye thus treated did not correspond in size to the normal pupil of 7 mm. but was several millimeters smaller, indicating a direct action of ergotoxine on the iris sphincter muscle. (See Table I.)

To Mr. Eugene Marti of the Sandoz Company we are indebted for a liberal supply of ergotamine tartrate.