Department of Craniofacial Growth and Development Dentistry, Kanagawa Dental College, 82 Inaoka-cho, Yokosuka, Kanagawa 238-8580, Japan.
Brain Res. 2012 Mar 29;1446:34-9. doi: 10.1016/j.brainres.2012.01.011. Epub 2012 Jan 16.
Chewing alters hypothalamic-pituitary-adrenal axis function and improves the ability to cope with stress in rodents. Given that stress negatively influences hippocampus-dependent learning and memory, we aimed to elucidate whether masticatory movements, namely chewing, improve the stress-induced impairment of spatial memory in conjunction with increased hippocampal glucocorticoid receptor expression. Male Sprague-Dawley rats were subjected to restraint stress by immobilization for 2h: the stress with chewing (SC) group were allowed to chew on a wooden stick during the latter half of the immobilization period, whereas the stress without chewing (ST) group were not allowed to do so. Performance in the Morris water maze test was significantly impaired in the ST group compared with the SC group. Further, the numbers of glucocorticoid receptor immunopositive neurons in the hippocampal cornu ammonis 1 region were significantly lower in the ST group than in the control and SC groups. The control and SC rats showed no significant differences in both the water maze performance and the numbers of glucocorticoid receptor-immunopositive neurons. The immunohistochemical finding correlated with the performance in the water maze test. These results suggest that chewing is a behavioral mechanism to cope with stress by increasing hippocampal glucocorticoid receptor expression.
咀嚼改变了下丘脑-垂体-肾上腺轴的功能，并提高了啮齿类动物应对压力的能力。鉴于压力会对海马体依赖的学习和记忆产生负面影响，我们旨在阐明咀嚼运动（即咀嚼）是否可以改善应激引起的空间记忆损伤，同时增加海马体糖皮质激素受体的表达。雄性 Sprague-Dawley 大鼠通过固定 2 小时来进行束缚应激：在固定期的后半段，允许咀嚼组啮齿动物咀嚼木棍，而不允许咀嚼组啮齿动物进行咀嚼。与咀嚼组相比，在固定组中，在 Morris 水迷宫测试中的表现明显受损。此外，在 ST 组中，海马体角状回 1 区的糖皮质激素受体免疫阳性神经元的数量明显低于对照组和 SC 组。在水迷宫表现和糖皮质激素受体免疫阳性神经元数量方面，对照组和 SC 组之间没有明显差异。免疫组织化学发现与水迷宫测试中的表现相关。这些结果表明，咀嚼是通过增加海马体糖皮质激素受体的表达来应对压力的行为机制。
