Huck U W, Lisk R D, Guyton C L
Biology Program, Sangamon State University, Springfield, IL 62708.
J Reprod Fertil. 1988 Nov;84(2):457-60. doi: 10.1530/jrf.0.0840457.
Hamsters were mated repeatedly at 60, 180, 300 and 420 days of age or once during their lifetime at one of these ages. Copulatory stimulation was varied both for number of ejaculations (2 versus 14) and amount of vaginocervical stimulation (5 versus 50-60 intromissions). Two ejaculations provided sufficient spermatozoa to maximize litter size for all age and parity classes tested. Differences in fecundity depended on the amount of vaginocervical stimulation received. Higher levels of vaginocervical stimulation increased littering success at 300 and 420 days for nulliparous females and at 180, 300 and 420 days for multiparous females. Females which did not deliver litters did not show a cessation of oestrous cycles which characteristically follows the induction of a luteal phase. The decreased fecundity observed with increasing age or parity therefore resulted from a change in sensitivity to the stimulus conditions necessary to activate the neuroendocrine arc for establishment of pregnancy.
仓鼠在60、180、300和420日龄时多次交配，或在这些年龄中的某一个时间进行一次终生交配。交配刺激在射精次数（2次与14次）和阴道宫颈刺激量（5次与50 - 60次插入）方面均有所不同。两次射精所提供的精子足以使所有测试年龄和胎次的产仔数最大化。生育力的差异取决于所接受的阴道宫颈刺激量。较高水平的阴道宫颈刺激增加了未生育雌性在300和420日龄时以及经产雌性在180、300和420日龄时的产仔成功率。未产仔的雌性并未表现出通常在黄体期诱导后出现的发情周期停止。因此，随着年龄或胎次增加而观察到的生育力下降是由于对激活神经内分泌弧以建立妊娠所需刺激条件的敏感性发生了变化。
