Rusak B
Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada.
J Pineal Res. 1988;5(1):41-50. doi: 10.1111/j.1600-079x.1988.tb00767.x.
A study of the effects of melatonin injections given to male Syrian hamsters (Mesocricetus auratus) late in the light phase in a 14L:10D photoperiod included control, oil-injected hamsters that had been transferred from a 16L:8D photoperiod. Many oil-injected hamsters underwent gonadal regression under these conditions. A literature review indicated that endocrine effects of 'control' injections are fairly common but that they might depend on previous photoperiodic history. A second study found that hamsters born and raised in 16L:8D had larger testes at 150 days of age than those raised in 14L:10D. Transfer from 16L:8D to 14L:10D caused some unhandled hamsters to show gonadal regression while transfer to 14L:10D combined with daily oil injections caused most hamsters to undergo gonadal regression. Injections in animals maintained in 14L:10D throughout the study did not cause gonadal regression. These results indicate that stress effects can confound interpretation of drug treatments that require daily injections. They also demonstrate that the endocrine system of male Syrian hamsters distinguishes two photoperiods that are longer than the critical daylength (12.5 h). The effects of shortening daylengths may be potentiated by environmental stressors; together these may trigger gonadal regression at variable annual phases in anticipation of the critical daylength.
一项关于在14小时光照：10小时黑暗的光周期中，在光照阶段后期给雄性叙利亚仓鼠（金仓鼠）注射褪黑素的影响的研究，包括对照组，即从16小时光照：8小时黑暗的光周期转移过来的注射油剂的仓鼠。在这些条件下，许多注射油剂的仓鼠出现了性腺退化。文献综述表明，“对照”注射的内分泌效应相当常见，但可能取决于先前的光周期历史。第二项研究发现，在16小时光照：8小时黑暗条件下出生并饲养的仓鼠在150日龄时的睾丸比在14小时光照：10小时黑暗条件下饲养的仓鼠更大。从16小时光照：8小时黑暗转移到14小时光照：10小时黑暗会导致一些未处理的仓鼠出现性腺退化，而转移到14小时光照：10小时黑暗并每日注射油剂会导致大多数仓鼠性腺退化。在整个研究过程中维持在14小时光照：10小时黑暗条件下的动物注射不会导致性腺退化。这些结果表明，应激效应会混淆对需要每日注射的药物治疗的解释。它们还表明，雄性叙利亚仓鼠的内分泌系统能够区分两个长于临界日长（12.5小时）的光周期。缩短日长的影响可能会因环境应激源而增强；这些因素共同作用，可能会在不同的年份阶段触发性腺退化，以预期临界日长的到来。
