Pseudopregnancy in female rats: Effects of hormonal manipulations of the male

Abstract

The stimulus determinants of pseudopregnancy were examined by mating female rats to castrated males maintained on estradiol benzoate (EB) or testosterone propionate (TP), or to intact males. Females were mated for five intromissions (5I), one ejaculatory series (1E), or three ejaculatory series (3E). Copulatory behavior was quite similar for males of all groups. Overall, females that copulated with EB males became pseudopregnant significantly less often than those females mated to TP or intact males. The amount of copulation (5I vs. 1E vs. 3E) received by females from functionally intact males influenced their probability of becoming pseudopregnant or pregnant. EB males had significantly lower body, penile, and seminal vesicle weights in addition to a greatly reduced complement of penile spines than either TP or intact males; adrenal weights did not differ. TP and intact males did not differ on any weight measure. These results indicate that some factor influenced by male hormonal status, possibly penile morphology, plays a role in the initiation of the functional luteal phase in laboratory rats.