Female Reproductive Tract

Short Day Lengths Delay Reproductive Aging

Abstract
Caloric restriction and hormone treatment delay reproductive senescence in female mammals, but a natural model of decelerated reproductive aging does not presently exist. In addition to describing such a model, this study shows that an abiotic signal (photoperiod) can induce physiological changes that slow senescence. Relative to animals born in April, rodents born in September delay their first reproductive effort by up to 7 months, at which age reduced fertility is expected. We tested the hypothesis that the shorter day lengths experienced by late-born Siberian hamsters ameliorate the reproductive decline associated with advancing age. Short-day females (10 h light/day) achieved puberty at a much later age than long-day animals (14 h light/day) and had twice as many ovarian primordial follicles. At 10 months of age 86% of females previously maintained in short day lengths produced litters, compared to 58% of their long day counterparts. Changes in pineal gland production of melatonin appear to mediate the effects of day length on reproductive aging; only 30% of pinealectomized females housed in short days produced litters. Exposure to short days induces substantial decreases in voluntary food intake and body mass, reduced ovarian estradiol secretion, and enhanced production of melatonin. One or more of these changes may account for the protective effect of short day lengths on female reproduction. In delaying reproductive senescence, the decrease in day length after the summer solstice is of presumed adaptive significance for offspring born late in the breeding season that first breed at an advanced chronological age.

Key words: Female Reproductive Tract • Ovary • Aging • Melatonin • Pineal

This article has been cited by other articles:

				E. W Kabithe and N. J Place Photoperiod-dependent modulation of anti-Mullerian hormone in female Siberian hamsters, Phodopus sungorus Reproduction, March 1, 2008; 135(3): 335 - 342. [Abstract] [Full Text] [PDF]

				M. P. Butler, J. J. Trumbull, K. W. Turner, and I. Zucker Timing of puberty and synchronization of seasonal rhythms by simulated natural photoperiods in female Siberian hamsters Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2007; 293(1): R413 - R420. [Abstract] [Full Text] [PDF]

				M. E Timonin, N. J Place, E. Wanderi, and K. E Wynne-Edwards Phodopus campbelli detect reduced photoperiod during development but, unlike Phodopus sungorus, retain functional reproductive physiology. Reproduction, October 1, 2006; 132(4): 661 - 670. [Abstract] [Full Text] [PDF]