Monosodium glutamate-induced arcuate nucleus damage affects both natural torpor and 2DG-induced torpor-like hypothermia in Siberian hamsters.
Monosodium glutamate-induced arcuate nucleus damage affects both natural torpor and 2DG-induced torpor-like hypothermia in Siberian hamsters.
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DOI：
10.1152/ajpregu.00387.2007
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发表时间：
2008
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影响因子：
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通讯作者：
K. Pelz;D. Routman;Joseph R. Driscoll;L. Kriegsfeld;J. Dark
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作者：
K. Pelz;D. Routman;Joseph R. Driscoll;L. Kriegsfeld;J. Dark
西伯利亚仓鼠 (Phodopus sungorus) 能够表现出每日的麻木状态，并将体温降低至约 15 摄氏度，从而显着节省能量消耗。仓鼠每天的麻木状态是由冬季的光周期引起的，并且与身体脂肪储备和慢性瘦素浓度的年度最低点同时发生。为了更好地了解迟钝背后的神经机制，西伯利亚仓鼠幼崽在出生后接受了盐水或味精处理，以消融可能拥有瘦素受体的弓状核神经元。对寒冷环境（10 摄氏度）的雄性和雌性仓鼠的体温进行了遥测研究，这些仓鼠进入了类似冬季的光周期（10:14-h 光-暗周期）（实验 1 和 2），或者保持在类似夏季的光周期（14:10-h 光-暗周期）（实验 3）。在实验 1 中，尽管其他光周期反应持续存在，但味精诱导的弓状核消融阻止了在盐水处理的西伯利亚仓鼠中观察到的光周期依赖性迟钝。经过味精处理的仓鼠往往拥有更多的脂肪储备。为了确定体脂肪的减少是否会增加味精处理后光周期诱导的麻木的频率，在实验 2 中，仓鼠接受了 2 周的食物限制（70% 随意）。尽管食物限制确实增加了味精和盐水处理的仓鼠的麻木频率，但它未能使经味精处理的仓鼠经历光周期依赖性麻木的比例正常化。在实验 3 中，与生理盐水处理的仓鼠相比，出生后味精处理使仓鼠进入 2DG 诱导的冬眠样低温的比例降低了约 50%（38% vs. 72%）。在那些确实出现体温过低的经味精处理的仓鼠中，其体温过低期间的最低体温显着高于经盐水处理的仓鼠。我们得出的结论是：1）弓状核机制介导光周期诱导的麻木，2）味精治疗也可以减少食物限制诱导的麻木，3）弓形核神经元对 2DG 诱导的麻木样低温做出了重要的（尽管是部分的）贡献。
Siberian hamsters (Phodopus sungorus) have the ability to express daily torpor and decrease their body temperature to approximately 15 degrees C, providing a significant savings in energy expenditure. Daily torpor in hamsters is cued by winterlike photoperiods and occurs coincident with the annual nadirs in body fat reserves and chronic leptin concentrations. To better understand the neural mechanisms underlying torpor, Siberian hamster pups were postnatally treated with saline or MSG to ablate arcuate nucleus neurons that likely possess leptin receptors. Body temperature was studied telemetrically in cold-acclimated (10 degrees C) male and female hamsters moved to a winterlike photoperiod (10:14-h light-dark cycle) (experiments 1 and 2) or that remained in a summerlike photoperiod (14:10-h light-dark cycle) (experiment 3). In experiment 1, even though other photoperiodic responses persisted, MSG-induced arcuate nucleus ablations prevented the photoperiod-dependent torpor observed in saline-treated Siberian hamsters. MSG-treated hamsters tended to possess greater fat reserves. To determine whether reductions in body fat would increase frequency of photoperiod-induced torpor after MSG treatment, hamsters underwent 2 wk of food restriction (70% of ad libitum) in experiment 2. Although food restriction did increase the frequency of torpor in both MSG- and saline-treated hamsters, it failed to normalize the proportion of MSG-treated hamsters undergoing photoperiod-dependent torpor. In experiment 3, postnatal MSG treatments reduced the proportion of hamsters entering 2DG-induced torpor-like hypothermia by approximately 50% compared with saline-treated hamsters (38 vs. 72%). In those MSG-treated hamsters that did become hypothermic, their minimum temperature during hypothermia was significantly greater than comparable saline-treated hamsters. We conclude that 1) arcuate nucleus mechanisms mediate photoperiod-induced torpor, 2) food-restriction-induced torpor may also be reduced by MSG treatments, and 3) arcuate nucleus neurons make an important, albeit partial, contribution to 2DG-induced torpor-like hypothermia.