Gene expression analysis and microdialysis suggest hypothalamic triiodothyronine (T3) gates daily torpor in Djungarian hamsters (Phodopus sungorus)
Gene expression analysis and microdialysis suggest hypothalamic triiodothyronine (T3) gates daily torpor in Djungarian hamsters (Phodopus sungorus)
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DOI：
10.1007/s00360-017-1086-5
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发表时间：
2017-07-01
影响因子：
2
通讯作者：
Herwig, Annika
中科院分区：
文献类型：
--
作者：
Bank, Jonathan H. H.;Cubuk, Ceyda;Herwig, Annika
甲状腺激素在调节哺乳动物的季节性适应中起着重要作用。一些研究表明，减少3，3 '，5-三碘甲状腺原氨酸（T3）在下丘脑的可用性是必需的生理适应冬季的Djungarian仓鼠。我们以前已经表明，T3参与日常麻木的调节，但目前还不清楚，T3是否影响麻木的中枢或外周机制。为了确定下丘脑内T3浓度在调节每日麻痹中的作用，我们检验了低下丘脑T3代谢有利于麻痹和高T3浓度不会的假设。在实验1中，评估了迟钝仓鼠中脑脊液和下丘脑细胞之间携带甲状腺激素的转运蛋白和下丘脑细胞内激活或失活T3的脱碘酶的基因表达。基因表达分析表明，减少T3在下丘脑细胞在麻痹。在实验2中，通过微透析改变下丘脑T3浓度，并通过植入体温变送器连续监测麻木行为。下丘脑T3浓度的增加降低了麻木的表达以及麻木的持续时间和深度。随后对第三脑室室管膜层基因表达的分析表明，T3失活脱碘酶3明显上调，但与仓鼠光周期适应相关的其他几个基因没有变化。最后，血清分析表明，增加总T3血清浓度是没有必要抑制迟钝的表达。总而言之，我们的结果与下丘脑内T3的可用性通过中枢途径显着有助于调节日常嗜睡的假设一致。
Thyroid hormones play an important role in regulating seasonal adaptations of mammals. Several studies suggested that reduced availability of 3,3',5-triiodothyronine (T3) in the hypothalamus is required for the physiological adaptation to winter in Djungarian hamsters. We have previously shown that T3 is involved in the regulation of daily torpor, but it remains unclear, whether T3 affects torpor by central or peripheral mechanisms. To determine the effect of T3 concentrations within the hypothalamus in regulating daily torpor, we tested the hypothesis that low hypothalamic T3 metabolism would favour torpor and high T3 concentrations would not. In experiment 1 gene expression in torpid hamsters was assessed for transporters carrying thyroid hormones between cerebrospinal fluid and hypothalamic cells and for deiodinases enzymes, activating or inactivating T3 within hypothalamic cells. Gene expression analysis suggests reduced T3 in hypothalamic cells during torpor. In experiment 2, hypothalamic T3 concentrations were altered via microdialysis and torpor behaviour was continuously monitored by implanted body temperature transmitters. Increased T3 concentrations in the hypothalamus reduced expression of torpor as well as torpor bout duration and depth. Subsequent analysis of gene expression in the ependymal layer of the third ventricle showed clear up-regulation of T3 inactivating deiodinase 3 but no changes in several other genes related to photoperiodic adaptations in hamsters. Finally, serum analysis revealed that increased total T3 serum concentrations were not necessary to inhibit torpor expression. Taken together, our results are consistent with the hypothesis that T3 availability within the hypothalamus significantly contributes to the regulation of daily torpor via a central pathway.