Abstract
Studies on the nervous mechanism involved in copulatory ovulation have disclosed several interesting facts. First, the sympathetic chain has been shown not to be essential for ovulation and pregnancy in the cat 1 or rat. 2 Secondly, mid-brain removal or section of the brain stem immediately after copulation does not prevent ovulation in the rabbit if the anterior pituitary is left intact. 3 These facts suggest that a nervous stimulus reaches the pituitary during copulation and that the pathway is probably independent of the sympathetics.
The purpose of this study has been to determine the effect of parasympathetic drugs on the process of ovulation. The first step was to determine whether or not these drugs alone would cause ovulation.
Adult female rabbits having been isolated 2 to 5 weeks and showing the typical vulval swelling and purple congestion of full oestrus were used. Four were treated with atropine sulfate (2 ½ mg./kg. intravenously); 2 with pilocarpine (1–3 mg./kg. every 2 hours for 6 hours); and 3 with physostigmine (¼ mg./kg. every hour for 6 hours). Laparotomy was performed in each case 48 hours after the last injection. Ovulation was not induced in any case. Ovaries in many animals showed signs of a decrease in oestrin secretion as was indicated by paling of the uteri and vulva. These rabbits, instead of ovulating, went out of oestrus immediately and refused to copulate for several days. This indicates that these drugs are inhibitory in their action rather than stimulatory.
To test this hypothesis, a series of 11 rabbits was injected with atropine as in the former series and allowed to copulate. The time which elapsed before copulation was different for each individual (1, 3, 4, 5, 7, 10 minutes, etc.), so that a complete series was obtained in which the time of drug action varied from 1–30 minutes.
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