THE EFFECT OF COCAINE ON THE IRIS COMPARED WITH ITS EFFECT ON CERTAIN OTHER STRUCTURES CONTAINING SMOOTH MUSCLE

¹ From the Department of Pharmacology, State University of Iowa, Iowa City, Iowa

Cocaine applied in ordinary amounts to the conjunctival sac of rabbits does not cause any appreciable weakening of the circular muscle of the iris, as measured by a subsequent physostigmine myosis.

Cocaine (1:10,000) applied to the isolated iris sphincter of steers or dogs produces no effect. Epinephrine (1:1,000,000) causes a marked relaxation.

On the isolated uterus of the rabbit, pregnant or nonpregnant, cocaine (1:10,000) causes an increase in rate of contractions and a marked increase in tone. Epinephrine (1:1,000,000) causes almost identical effects.

On the uterus of the non-pregnant cat the sympathetics are inhibitory. Here cocaine causes inhibition of contractions and a temporary rise in tone followed by prolonged fall in tone.

Epinephrine (1:1,000,000) causes inhibition of contractions and an immediate fall in tone.

On the isolated small intestine, cocaine (1:10,000) causes a loss of tone and inhibition of amplitude of contractions. There is later an increase in tone. Epinephrine (1:1,000,000) causes a loss in tone and a temporary inhibition of rhythmic contractions.

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