Action of Pilocarpine and Atropine on Uterine Fistulae in the Unanesthetized Rabbit

Abstract

The effect of pilocarpine and atropine on the uterine fistula of the unanesthetized rabbit has been observed. The data include observations of 18 injections of pilocarpine and 14 injections of atropine on 5 rabbits over several different days. The method of recording such motility has been described. 1 , 2 Adult female rabbits (albino, chinchilla and brown) were castrated at the time of operation. On the day prior to the experiment, 25-50 r.u. of oestrin (Theelin; Theelol from Parke, Davis and Co.) were administered when marked motility was desired. 3 When quiescence was desired, the castrated rabbit was untreated. 3 The effects noted are as follows:

Pilocarpine-HCl. When pre-injection motility is rhythmical in character and of marked amplitude, pilocarpine (0.6-6 mg.) administered intravenously promptly elicits a sustained contraction lasting one to 4 or more minutes. The contractions which follow are frequently of greater duration and increased frequency. The amplitude of these contractions seems not to be regularly affected. When the uterus is relatively quiescent, as recorded by the balloon method, pilocarpine is without effect, or else it elicits a feeble sustained contraction. It is the impression of the observer that when this takes place it occurs in association with other effects of the pilocarpine (cyanosis and pulmonary distress). The non-responsiveness of the quiescent uterine fistula to pilocarpine is similar to its non-responsiveness to posterior pituitary extracts 4 and in anaphylactic shock. 5 Epinephrine, however, does elicit a sustained uterine contraction of the quiescent uterine fistula.

Atropine-sulphate. This drug (1-5 mg.) by itself has no observable effect on either the contracting or quiescent uterine fistula. Its action is limited to (a) preventing a response to subsequent administrations of pilocarpine (the duration of this antagonism varied from 9 minutes in one instance to 30 minutes in another); (b) causing relaxation of a uterus already contracted under the influence of pilocarpine.