A gene controlling male pheromonal facilitation of PMSG-induced ovulation in mice.

was postulated that this system existed as a single gene (Chapman & Whitten, 1968), the following experiments were conducted to determine the heritability of the male pheromonal system involved in pmsg-induced facilitation of ovulation. Female mice of the C57BL/6J and SWR/J strains were housed, one per cage, following weaning at 21 days of age. Lighting was kept on a 12 hr on/12 hr off schedule (on at 06.00, off at 18.00 hours). At 09.00 hours on the 24th day of age, each mouse was injected subcutaneously with 2 i.u. pmsg (Ayerst-Equinex). It had previously been shown that this dose of pmsg did not cause ovulation at 24 hr in these strains of mice (Christenson & Eleftheriou, 1972). At noon on the 2nd day (51 hr later), each female was transferred to a cage with a double wire partition. The female was housed on the side which the male had used previously and the male was transferred to the opposite side. All females were killed approximately 21 hr later, i.e. 72 to 74 hr after pmsg injection, and the oviducts were removed for examination under a dissecting microscope at 40 magnification. Ova were counted and the state of the ova, i.e. whether clumped, denuded, etc. (Zarrow, Caldwell, Hafez & Pincus, 1958), was recorded. Eighteen females of strain C57BL/6J were exposed to C57BL/6J males and another eighteen females were exposed to SWR/J males. Similarly, eighteen females of strain SWR/J were exposed to C57BL/6J and eighteen to SWR/J males. For controls, another eighteen females of each strain were injected with pmsg, and transferred to a clean cage but were not exposed to a male, while a further eighteen females were injected with saline alone and also were not