Meeting Abstract

29.5  Monday, Jan. 5  Graded inhibition of reproductive physiology by short photoperiod and aging outcomes in female Siberian hamsters, Phodopus sungorus PLACE, Ned J; Cornell University njp27@cornell.edu

Reproductive aging has been shown to be decelerated in female Siberian hamsters raised in short days (SD), and delayed puberty induced by SD rearing was thought to be a plausible explanation for the later effects on aging. However, in the present study, signs of decelerated reproductive aging were evident in female hamsters that were first exposed to SD as adults. As compared to females held in long days (LD), hamsters that had been transferred to SD from 3 to 9 months of age showed better mating success when first bred at 12 months. Moreover, the number of ovarian primordial follicles, which represents the resting pool of germ cells, was greater in females held in SD than in LD, but only in those SD females that demonstrated the most immediate and sustained photo-inhibition. Females exhibiting a more modest response to SD had primordial follicle numbers at 9 and 12 months of age that were low and comparable to those found in age-matched LD females and in SD-nonresponders. Similarly, for females that were gestated and held in SD through 6 months of age, delayed photo-refractoriness and onset of vaginal patency were associated with greater numbers of primordial follicles at later ages. These results highlight the importance of assessing individual responses to environmental cues, as the categorization of animals as responders or nonresponders fails to capture the gradations of the photo-inhibitory effect. This concept may help explain the variation within groups in the levels of a circulating hormone that appears to reflect the size of the ovarian follicular reserve, anti-Mullerian hormone (AMH). Hamsters demonstrating the most robust response to SD, either before or after puberty, have the greatest numbers of primordial follicles at advanced ages and the highest levels of serum AMH.