SEX AND STRAIN INVOLVEMENT IN PHEROMONAL FACILITATION OF GONADOTROPHIN-INDUCED OVULATION IN THE MOUSE

Summary. Three strains of mice (SWR/J, C57BL/6J and BALB/cJ) were examined for pheromonal facilitation of both PMSG- and HCG\x=req-\ induced ovulation. Immature females were injected with sufficient levels of the hormones to induce minimal egg release. Exposure to adult males involved the use of both the homologous and heterologous strains. The SWR/J and BALB/cJ females showed significant facilitation of ovulation with either gonadotrophin and exposure to adult males of the same or heterologous strain. Exposure of the three strains of females to C57BL/6J males, however, failed to result in any facilitation; but exposure of the C57BL/6J females to males of the SWR/J and BALB/cJ strains did result in facilitation. It may be concluded that the failure of pheromonal facilitation in the C57BL/6J strain is due to an inability of the males of this strain to produce the pheromone. The C57BL/6J females, however, still possess the ability to respond and, consequently, have not lost the receptors for the pheromone.