Ruby N F, Heller H C
Department of Biological Sciences, Stanford University, CA 94305-5020, USA.
J Biol Rhythms. 1996 Jun;11(2):126-36. doi: 10.1177/074873049601100205.
Temperature compensation of circadian rhythms in neuronal firing rate was investigated in the suprachiasmatic nucleus (SCN) of ground squirrels and rats in vitro. A reduction in SCN temperature from 37 to 25 degrees C reduced peak firing rates by > 70% in rats but only by approximately 21% in squirrels; trough firing rates were marginally altered in both species. In the rat SCN at 25 degrees C, the peak in neuronal activity decreased progressively on successive days and circadian rhythms no longer were present by Day 3. There was a 37% reduction in the number of single units detected and an increase in the temporal variability of peak firing rates among individual rat SCN neurons at low temperature. By contrast, single units were readily detected and circadian rhythms were robust in squirrels at 37 and 25 degrees C; a Q10 of 0.927 was associated with a shortening of tau by 2 h and a 5-h phase change after only 48 h at low temperature. These results suggest that temperature can have a substantial impact on circadian organization in a mammalian pacemaker considered to be temperature compensated.
在体外对松鼠和大鼠的视交叉上核（SCN）中神经元放电频率的昼夜节律温度补偿进行了研究。将SCN温度从37℃降至25℃，大鼠的峰值放电频率降低了70%以上，但松鼠仅降低了约21%；两个物种的谷值放电频率均略有改变。在25℃的大鼠SCN中，神经元活动的峰值在连续几天中逐渐降低，到第3天昼夜节律不再存在。在低温下，检测到的单个神经元数量减少了37%，并且大鼠单个SCN神经元的峰值放电频率的时间变异性增加。相比之下，在37℃和25℃的松鼠中很容易检测到单个神经元，并且昼夜节律很强；在低温下仅48小时后，0.927的Q10与tau缩短2小时和5小时的相位变化相关。这些结果表明，温度可能会对被认为具有温度补偿功能的哺乳动物起搏器中的昼夜节律组织产生重大影响。
