Jefimow Małgorzata, Wojciechowski Michał, Tegowska Eugenia
Department of Animal Physiology, Institute of General and Molecular Biology, N. Copernicus University, Gagarina 9 Street, PL 87-100 Toruń, Poland.
Comp Biochem Physiol A Mol Integr Physiol. 2003 Apr;134(4):717-26. doi: 10.1016/s1095-6433(02)00373-2.
Daily variations in sensitivity to noradrenaline (NA) and the activation of nonshivering thermogenesis (NST) are important for survival under a potentially wide range of environmental conditions. However, little is known regarding the ability of the Siberian hamster and other species to activate NST in the day and night when they may be subjected to marked variations in environmental temperature. In this study, the effects of acclimation temperature and time of day on the behavioral thermoregulatory response to NA injections in Siberian hamsters (Phodopus sungorus) was investigated. Hamsters were acclimated for 4 weeks to 23 degrees C and a L:D 12:12 h photoperiod. After acclimation, preferred ambient temperatures (PT(a)) in saline- and NA-injected animals were measured continuously in the temperature gradient system. NA (0.6 mg/kg; s.c.) was given every 4 h while PT(a) was monitored. After NA injections there was a rapid drop in PT(a), decreasing to approximately 15 degrees C within 10-20 min after each NA injection. Following 4 weeks of acclimation to 10 degrees C and a L:D 8:16 h photoperiod, the same hamsters were re-tested in the temperature gradient system. Cold acclimation led to an accentuation in the behavioral response with a decrease in PT(a) of approximately 10 degrees C. The maximal decrease in preferred ambient temperatures was recorded during the light phase of the day and during the second part of the night. Lowering of PT(a) after NA allows for rapid dissipation of the heat from NST. Overall, the behavioral response reflects the daily changes in brown adipose tissue sensitivity to NA and thus capacity for NST.
对去甲肾上腺素（NA）的敏感性以及非颤抖性产热（NST）的激活存在每日变化，这对于在潜在广泛环境条件下的生存至关重要。然而，关于西伯利亚仓鼠和其他物种在白天和夜晚环境温度可能发生显著变化时激活NST的能力，我们所知甚少。在本研究中，我们调查了驯化温度和一天中的时间对西伯利亚仓鼠（Phodopus sungorus）对NA注射的行为体温调节反应的影响。仓鼠在23摄氏度和12小时光照：12小时黑暗的光周期下驯化4周。驯化后，在温度梯度系统中连续测量注射生理盐水和NA的动物的偏好环境温度（PT(a)）。每4小时给予一次NA（0.6毫克/千克；皮下注射），同时监测PT(a)。注射NA后，PT(a)迅速下降，每次注射NA后10 - 20分钟内降至约15摄氏度。在适应10摄氏度和8小时光照：16小时黑暗的光周期4周后，对同一批仓鼠在温度梯度系统中重新进行测试。冷驯化导致行为反应加剧，PT(a)下降约10摄氏度。在白天的光照阶段和夜晚的后半段记录到偏好环境温度的最大下降。注射NA后PT(a)的降低有利于NST产生的热量快速消散。总体而言，行为反应反映了棕色脂肪组织对NA敏感性的每日变化，从而反映了NST的能力。
