Talan M I, Kirov S A, Kosheleva N A
Gerontology Research Center, National Institute on Aging, Baltimore, Maryland 21224, USA.
Exp Gerontol. 1996 Nov-Dec;31(6):687-98. doi: 10.1016/s0531-5565(96)00095-2.
Twelve- and 28-month-old C57BL/6J male mice were housed either at room temperature of 22 degrees C or at thermoneutrality (29 degrees C) during the two months prior to experiments. Acute experiments were conducted under anesthesia, myorelaxation, and artificial ventilation. We recorded efferent electrical impulse activity in one of the sympathetic nerves innervating the interscapular brown adipose tissue in response to acute cold stimulation, when body temperature was lowered 7.5 degrees C below control level. In separate experiments we measured O2 consumption and CO2 production and calculated the nonshivering thermogenesis. We also measured the concentration of uncoupling protein in interscapular brown adipose tissue before and after three-hour cold stress. In aged mice, both sympathetic nervous activity and nonshivering thermogenesis were lower in animals housed at thermoneutrality (29 degrees C) than in mice housed at 22 degrees. Among mice maintained at 22 degrees C, but not at thermoneutrality, aged animals had greater nonshivering thermogenesis and greater cold induced concentration of uncoupling protein in the brown adipose tissue than adults. Sympathetic nervous outflow to brown adipose tissue was always greater in aged mice, regardless of the temperature of acclimation. We concluded that aged mice, housed at 22 degrees C, showed the changes in nonshivering thermogenesis associated with cold acclimation. However, an increased sympathetic outflow to brown adipose tissue in aged animals reflects an age-related elevation of the tone and responsiveness of the sympathetic nervous system.
在实验前两个月，将12月龄和28月龄的C57BL/6J雄性小鼠分别饲养在22摄氏度的室温环境或热中性环境（29摄氏度）中。急性实验在麻醉、肌肉松弛和人工通气条件下进行。当体温降至比对照水平低7.5摄氏度时，我们记录了支配肩胛间棕色脂肪组织的一条交感神经中的传出电冲动活动，以响应急性冷刺激。在单独的实验中，我们测量了氧气消耗和二氧化碳产生，并计算了非寒战产热。我们还测量了3小时冷应激前后肩胛间棕色脂肪组织中解偶联蛋白的浓度。在老年小鼠中，饲养在热中性环境（29摄氏度）中的动物的交感神经活动和非寒战产热均低于饲养在22摄氏度环境中的小鼠。在维持在22摄氏度而非热中性环境的小鼠中，老年动物比成年动物具有更大的非寒战产热以及棕色脂肪组织中更大的冷诱导解偶联蛋白浓度。无论适应温度如何，老年小鼠中流向棕色脂肪组织的交感神经输出总是更大。我们得出结论，饲养在22摄氏度环境中的老年小鼠表现出与冷适应相关的非寒战产热变化。然而，老年动物中流向棕色脂肪组织的交感神经输出增加反映了与年龄相关的交感神经系统张力和反应性的升高。
