研究背景：運動已知可提升大腦功能，如: 改變神經活性和神經可塑性，這些改變被認為與腦源性神經滋養因子（BDNF）有關。c-fos是一種即早基因，常被用來標識活性改變的神經細胞。有研究指出運動會增加大腦中某些腦區的c-Fos蛋白表現量，尤其是海馬回。然而，運動是否會影響整個腦，或是只有特定腦區，則並不清楚。
研究目的：瞭解那些腦區的神經活性會被跑步運動所影響。
實驗方法：八周大的C57BL/6J小鼠進行一次（急性）、或為期一個月（長期）的中強度跑步機運動，每次一小時。一部分的急性運動小鼠在跑步後，立即斷頭取腦（以下簡稱E1h組），另一部分則在休息兩小時後，才斷頭取腦（以下簡稱E1hS2h組）。急性運動控制組的小鼠，則沒有跑步，直接斷頭取腦（以下簡稱Ctrl組）。長期運動的小鼠，在最後一次跑步後，部分會立即斷頭取腦（以下簡稱1M-E1h組），另一部分則在休息兩小時後，才斷頭取腦（以下簡稱1M-E1hS2h組）。長期運動控制組的小鼠，則停掉最後一次跑步，與1M-E1h組同時斷頭取腦（以下簡稱1M-Ctrl組）。腦組織固定後，切成25 μm的切片，以組織免疫染色法對c-Fos蛋白進行染色，並在下列腦區進行計數：大腦皮質(運動皮質和體感皮質)、邊緣區(扣帶皮質、梨狀皮質、中隔內核、海馬回及杏仁核)、基底核(殼/尾狀核、伏隔核心)、間腦(視丘、下視丘)、腦幹(黑質區、腹側被蓋區、上丘、側水管周灰質、中縫背核、橋腦核)和小腦(前葉和後葉)。另一組小鼠腦組織切成一級運動皮質、一級體感皮質、背側海馬回、腹側海馬回、杏仁核、殼/尾狀核、視丘和下視丘，以西方墨點法對BDNF蛋白的表現量進行測量。
結果： 相較於Ctrl組， E1h組的c-Fos+ 細胞密度，在大腦皮質、海馬回及基底核區較高；而到了E1hS2h時，只剩海馬回內的一些區域仍然高於Ctrl組。在長期運動小鼠，大腦皮質、邊緣區、基底核、間腦及腦幹的側水管周灰質的c-Fos+ 細胞密度在1M-E1h 組高於1M-Ctrl組；到了1M-E1hS2h時，只有海馬回內的一些區域、梨狀皮質、殼/尾狀核、下視丘和側水管周灰質的c-Fos+ 細胞密度仍然高於1M-Ctrl組。雖然，急性運動並不影響BDNF蛋白的表現量，但是，BDNF蛋白增加的量和c-Fos+ 細胞密度增加的量，呈顯著正相關。
結論： 無論是急性運動或是長期運動，大腦皮質、海馬回、以及基底核的神經活性都會受到影響而增加；而間腦和腦幹則只會受到長期運動的影響。急性運動所增加的c-Fos+細胞密度和所增加的BDNF表現量呈正相關。因此，運動可作為一非藥物、保護大腦的策略，尤其是那些對運動有反應的腦區。

Background: Exercise benefits brain functions, such as increases neuronal activity and synaptic plasticity, which has been linked to brain-derived neurotrophic factor (BDNF). c-fos, an immediate early gene, is frequently used as neuron activation marker. Exercise increases the expression of c-Fos in some brain regions, such as hippocampus. However, it is unclear whether the effect of exercise on brain is ubiquitous or is a region-specific phenomenon.
Objective: To identify the brain regions sensitive to running.
Methods: C57BL/6J mice, 8-week-old, were forced to run on a treadmill at moderate intensity, one hour each time. The mice were assigned to the single-bout (acute) or one month (long-term) exercise group. The mice were either killed immediately (acute: E1h; long-term: 1M-E1h) or 2 h after (acute: E1hS2h; long-term: 1M-E1hS2h) the 1 h running. Mice of the acute control group (Ctrl) were killed without running. Mice of the long-term control group (1M-Ctrl) omitted the last run and killed at the same time as the 1M-E1h group. The brains were cut at 25 μm and immunostained for c-Fos. The number of c-Fos+ cells was counted in the following brain regions: cortex (motor cortex, somatosensory cortex), limbic area (cingulate, piriform cortex, septal nucleus, hippocampus, amygdala), basal nuclei (caudate/putamen, accumbens nucleus core), diencephalon (thalamus, hypothalamus), brain stem (substantia nigra, ventral tegmental area, superior colliculus, lateral periaqueductal gray, dorsal raphe nucleus, pontine nucleus) and cerebellum (anterior and posterior lobes). Some of the brains were dissect into primary motor cortex, primary somatosensory cortex, dorsal and ventral parts of hippocampus, amygdala, caudate/putamen, thalamus and hypothalamus to measure the levels of BDNF.
Results: Compared to the Ctrl group, the density of c-Fos+ cells was increased in the cortex, hippocampus and basal nuclei of E1h group. In the E1hS2h group, a few regions of hippocampus were still higher than those of the Ctrl group. In the long-term exercise mice, the density of c-Fos+ cells of cortex, limbic area, basal nuclei, diencephalon and lateral periaqueductal gray of brain stem in the 1M-E1h group were higher than those of 1M-Ctrl group. The density of c-Fos+ cells in the regions of hippocampus, piriform cortex, caudate/putamen, hypothalamus and lateral periaqueductal gray remained elevated in the 1M-E1hS2h group. Although the levels of BDNF were not affected by acute exercise, the changed levels of BDNF were positively correlated with the changed density of c-Fos+ cells.
Conclusion: Both in acute and long-term exercises influence neuronal activity in the cortex, hippocampus and basal nuclei, while neuronal activity in the diencephalon and brain stem were only influenced by long-term exercise. Acute exercise-induced changes in the BDNF levels were positively correlated with changes in the density of c-Fos+ cells. Physical exercise may serve as a non-pharmaceutical means to protect brain, especially those regions responding to exercise training.

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