Concering the relationship between the sexual cycle in albino rats and the autonomic nervous system, opinions are divided among workers. The principal reason for this difference in the opinions seems to lie especially in the methods employed in the application of autonomic drugs. Thus far most of investigators have administered autonomic drugs daily over a long period, but in the belief that for the solution of this problem it would seem to be more effectiv to administer repeatedly an adequate dose of these drugs for a short period of time, the author studied by this method the effect of pilocarpine on the sexual cycle of albino rats and reported that stimulation or tonic increase of the parasympathetic nervous system inhibited the development of ovarian follicles. In the present experiment for the purpose to verify this contention, the author used esmodil which is a chemical analogue of acetylcholine and has several pharmacological effects similar to the latter but whose effect on the sexual cycle remains obscure. As the results the following data were obtained.
1. The injection of esmodil in the dose of 0.1-0.15 mg repeated three times a day for 4 days beginning from proestrus arrested the sexual cycle for 6 to 14 days. In addition, there could be observed the findings in the ovary and uterus which corresponded such a suppression.
2. When esmodil was used concurrently with atropine, such a suppressing effect was practically all inhibited.
3. Consequently, these findings support considerably the author's contention that the stimulation or the tonic increase of the parasympathetic nervous system inhibits the development of the ovarian follicles.