Physiology, School of Medical Sciences, and Bosch Institute, The University of Sydney, NSW 2006, Australia.
Gen Comp Endocrinol. 2012 Nov 1;179(2):265-76. doi: 10.1016/j.ygcen.2012.08.024. Epub 2012 Sep 5.
Seasonal cycles of reproduction are common in many mammals and these are combined with the necessary energy budgeting for thermoregulatory challenges. Many mammals meet the challenge of changing environmental temperatures in winter by using torpor, a controlled reduction in body temperature and metabolic rate. We aimed to determine the effects of photoperiod and reproductive hormones on the seasonal cycles of reproduction and torpor use in a marsupial that commences reproduction in winter, the stripe-faced dunnart, Sminthopsis macroura. Males and females were placed under LD 14:10 and natural reproductive hormones blocked by either flutamide (males) or mifepristone (females) or tamoxifen (females). Reproductive parameters, metabolic rate and torpor variables were determined. The same animals were then placed under LD 10:14 and given testosterone (males) or progesterone (females) or oestrogen (females). Reproductive parameters, metabolic rate and torpor variables were measured. Body mass and tail widths (fattening indicator) in males were significantly affected by testosterone, and the effects were reversed by hormone blockers. Reproductive parameters were unaffected. Resting metabolic rate and ability to use torpor were not affected by treatment in males, however torpor characteristics, especially torpor bout duration, were affected by presence of testosterone in males. In females, body mass was unaffected by hormone presence, although tail widths were affected. Disruption of reproductive cycles occurred with hormone blockers in females, however, resting metabolic rate was not affected, and only presence of progesterone affected torpor characteristics in females. Our results differ from those found for rodents, where presence of testosterone abolishes the use of torpor in males, and oestrogen inhibits torpor use in females. Our study suggests that, in this mammal, metabolic responses to the presence or absence of reproductive hormones differs between males and females, and there is no absolute endocrinologically-driven reproductive season demarcated from the torpor season.
许多哺乳动物的繁殖具有季节性周期，这些周期与应对体温调节挑战所需的能量预算相结合。许多哺乳动物通过使用蛰伏来应对冬季环境温度的变化，蛰伏是一种控制体温和代谢率降低的现象。我们的目的是确定光周期和生殖激素对季节性繁殖周期和蛰伏使用的影响，这种现象发生在冬季开始繁殖的有袋动物条纹脸袋狸（Sminthopsis macroura）身上。雄性和雌性动物被置于 LD 14:10 光照条件下，并通过氟他胺（雄性）、米非司酮（雌性）或他莫昔芬（雌性）阻断天然生殖激素，或置于 LD 10:14 光照条件下，并给予睾丸酮（雄性）、孕酮（雌性）或雌激素（雌性）。测定了生殖参数、代谢率和蛰伏变量。然后，对相同的动物进行 LD 10:14 光照处理，并给予睾丸酮（雄性）、孕酮（雌性）或雌激素（雌性）。测量了生殖参数、代谢率和蛰伏变量。雄性动物的睾丸酮对其体重和尾巴宽度（肥胖指标）有显著影响，而激素阻断剂则逆转了这种影响。生殖参数不受影响。雄性动物的静止代谢率和使用蛰伏的能力不受处理的影响，但蛰伏特征，尤其是蛰伏持续时间，受雄性动物睾丸酮的影响。在雌性动物中，激素的存在并不影响其体重，但会影响其尾巴宽度。在雌性动物中，激素阻断剂会扰乱生殖周期，但不会影响静止代谢率，只有孕酮的存在会影响雌性动物的蛰伏特征。我们的研究结果与啮齿动物的研究结果不同，在啮齿动物中，睾丸酮的存在会使雄性动物停止使用蛰伏，而雌激素会抑制雌性动物使用蛰伏。我们的研究表明，在这种哺乳动物中，雄性和雌性对生殖激素的存在或缺失的代谢反应不同，而且没有绝对的内分泌驱动的繁殖季节与蛰伏季节分开。
