Monecke Stefanie, Wollnik Franziska
Biological Institute, Department of Animal Physiology, University of Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany.
J Comp Physiol B. 2005 Apr;175(3):167-83. doi: 10.1007/s00360-005-0472-6. Epub 2005 Feb 22.
European hamsters (Cricetus cricetus) show pronounced seasonal changes in their physiology and behavior. The present study provides a detailed analysis of the temporal relationship between seasonal cycles of reproduction and body mass and seasonal changes of two circadian parameters, i.e., locomotor activity and 6-sulphatoxymelatonin (aMT6s) excretion, in individual animals kept under natural light conditions. Our results demonstrate a characteristic pattern of locomotor activity and aMT6s excretion observed around the summer solstice, i.e., from mid-May to mid-July. During this time, locomotor activity was characterized by a high level of activity and an early activity onset, while the nightly elevation of melatonin was reduced to baseline levels. These seasonal changes in aMT6s excretion and locomotor activity were only loosely related to changes in the reproductive status of the animals, but correlated well with a period of the annual cycle during which the animals were sensitive to short days. They may therefore reflect a specific state of the circadian pacemaker system within the SCN and can thus be a valuable tool to further characterize molecular and physiological mechanisms of photoperiodic time measurements in European hamsters.
欧洲仓鼠（Cricetus cricetus）在生理和行为上表现出明显的季节性变化。本研究详细分析了在自然光条件下饲养的个体动物中，繁殖季节周期与体重之间的时间关系，以及两个昼夜节律参数（即运动活动和6-硫酸氧褪黑素（aMT6s）排泄）的季节性变化。我们的结果表明，在夏至前后（即5月中旬至7月中旬）观察到了运动活动和aMT6s排泄的特征模式。在此期间，运动活动的特点是活动水平高且活动开始时间早，而夜间褪黑素的升高则降至基线水平。aMT6s排泄和运动活动的这些季节性变化与动物繁殖状态的变化仅存在松散的关联，但与动物对短日照敏感的年度周期阶段密切相关。因此，它们可能反映了视交叉上核内昼夜节律起搏器系统的特定状态，从而可以成为进一步表征欧洲仓鼠光周期时间测量的分子和生理机制的有价值工具。
