Florant G L, Tamarkin L
Biol Reprod. 1984 Mar;30(2):332-7. doi: 10.1095/biolreprod30.2.332.
Plasma melatonin concentrations were measured in marmots (Marmota flaviventris) maintained under three short-day (4L:20D; 8L:10D; 10L:14D) and one long-day (14L:10D) photoperiod(s). Each animal had a daily rhythm of plasma melatonin with elevated plasma melatonin levels occurring during the dark period of the lighting cycle. There were no significant differences between any peak values during the night. The mean duration of elevated night melatonin concentrations was significantly different between long-day (16L:8D) and 8L:16D or 4L:20D animals (P less than 0.01). Daytime plasma melatonin levels were not significantly different among the photoperiods. These results characterize plasma melatonin rhythms in a sciurid rodent and demonstrate that this rhythm is modified by photoperiod. Therefore, the plasma melatonin profile could convey information about day length to the animal or, alternatively, the rhythm may be acting as a time-keeping mechanism for other physiological functions.
在处于三种短日照（4小时光照：20小时黑暗；8小时光照：10小时黑暗；10小时光照：14小时黑暗）和一种长日照（14小时光照：10小时黑暗）光周期条件下的旱獭（黄腹旱獭）中测量了血浆褪黑素浓度。每只动物的血浆褪黑素都有每日节律，血浆褪黑素水平在光照周期的黑暗期升高。夜间的任何峰值之间均无显著差异。长日照（16小时光照：8小时黑暗）与8小时光照：16小时黑暗或4小时光照：20小时黑暗的动物相比，夜间褪黑素浓度升高的平均持续时间有显著差异（P小于0.01）。不同光周期之间白天的血浆褪黑素水平无显著差异。这些结果描述了一种松鼠科啮齿动物的血浆褪黑素节律，并表明这种节律受光周期影响。因此，血浆褪黑素概况可能会向动物传达有关白昼长度的信息，或者，这种节律可能作为其他生理功能的计时机制。
