Biology of Reproduction, Vol 1, 302-306, Copyright © 1969 by Society for the Study of Reproduction

Strange Male Pregnancy Block in Deermice: Prolactin and Adrenocortical Hormones

¹ The Jackson Laboratory, Bar Harbor, Maine 04609

A total of 538 inseminated prairie deermice were used in four experiments to evaluate possible roles for ACTH, adrenocorticosteroids, and prolactin in the mechanism by which blocked pregnancies follow exposure to strange males. The first experiment revealed increased plasma corticosterone (unbound) in inseminated females at 2 and possibly at 24 hr after initiation of exposure to a strange male. There was no change in this hormone fraction during re-exposure to the original stud male when compared to isolated controls. Implantation success was evaluated in three additional experiments: (a) in adrenalectomized vs. sham-operated females exposed to strange males or not; (b) following single injections of 1-8 IU ACTH on the day after insemination in otherwise undisturbed females; and (c) following strange male exposure with or without concurrent daily injections of prolactin (2 mg—about 50 IU—per day for 4 days). The inhibitory effect of the strange male on implantation was not altered by adrenalectomy nor was implantation success affected by any dose of ACTH in intact undisturbed females. ACTH is thus released during strange male exposure but neither the increased release of ACTH nor the resulting increased circulation of adrenocorticosteroids appear to be responsible for the blocked pregnancies. Normal implantation success resulted if prolactin was given to the female during strange male exposure (as it is known to do in house mice).