Ten derivatives of halo propanediol were tested orally for male antifertility effects in adult Sprague-Dawley rats. Six of these compounds were effective in inducing temporary sterility at a daily dose ranging from 2\m=.\5to 5 mg/rat. When administered over a minimum period of 7 days, these minimum effective doses did not interfere with the mating behaviour and spermatogenesis even during prolonged medication. However, at ten times the minimum effective dose, Compounds III (1-chloro-2,3-propanediol) and VII (1-chloro-2,3-bis[tetrahydropyran-2-yloxy]propane) caused severe testicular damage and irreversible sterility, while Compound X (4-[chloromethyl]-2-pentyl-1,3-dioxolane) did not. Our studies confirm that the presence of an \g=a\-chlorohydrin group is essential in halo propanediol derivatives for antifertility effects in male rats.

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A correlation observed between the vaginal cornification and the presence of freshly shed ova in the fallopian tube in a strain of 4-day cyclic rats was altered by administering medroxyprogesterone acetate (MPA) and chlorpromazine (CPZ). MPA, given 1 day before proestrus, blocked vaginal cornification, uterine fluid imbibition, and ovulation. A single injection of human chorionic gonadotropin (HCG), given on the expected day of proestrus, induced ovulation in all MPA-treated rats, but did not induce estrogenic parameters. CPZ, given at noon on the day of proestrus, also blocked ovulation, but did not alter the estrogenic effects. Again, HCG induced ovulation in CPZ-treated rats. These data indicate that MPA and CPZ have a similar pharmacologic effect at the hypothalamus–pituitary axis, while acting differently at the estrogenic receptor sites.

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Various hormonal methods are compared of obtaining pseudopregnant rats capable of implanting fertilized ova transferred to them. Injection of 20 \g=m\g of oestrone to rats on Day 1 of pregnancy, followed by injection of 1 mg/day of medroxyprogesterone on Days 2 to 4, resulted in a high rate of implantation of fertilized ova transferred on Day 5. Non-pregnant rats were able to implant ova transferred to them when injected with prolactin, but not with progesterone. Indirect evidence is presented which indicates that the ability to implant ova is not absolute but may vary in degree among rats receiving different treatments.