Hale M W, Hay-Schmidt A, Mikkelsen J D, Poulsen B, Shekhar A, Lowry C A
Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA.
Neuroscience. 2008 Aug 26;155(3):659-72. doi: 10.1016/j.neuroscience.2008.05.054. Epub 2008 Jun 14.
Anxiety states and anxiety-related behaviors appear to be regulated by a distributed and highly interconnected system of brain structures including the basolateral amygdala. Our previous studies demonstrate that exposure of rats to an open-field in high- and low-light conditions results in a marked increase in c-Fos expression in the anterior part of the basolateral amygdaloid nucleus (BLA) compared with controls. The neural mechanisms underlying the anatomically specific effects of open-field exposure on c-Fos expression in the BLA are not clear, however, it is likely that this reflects activation of specific afferent input to this region of the amygdala. In order to identify candidate brain regions mediating anxiety-induced activation of the basolateral amygdaloid complex in rats, we used cholera toxin B subunit (CTb) as a retrograde tracer to identify neurons with direct afferent projections to this region in combination with c-Fos immunostaining to identify cells responding to exposure to an open-field arena in low-light (8-13 lux) conditions (an anxiogenic stimulus in rats). Adult male Wistar rats received a unilateral microinjection of 4% CTb in phosphate-buffered saline into the basolateral amygdaloid complex. Rats were housed individually for 11 days after CTb injections and handled (HA) for 2 min each day. On the test day rats were either, 1) exposed to an open-field in low-light conditions (8-13 lux) for 15 min (OF); 2) briefly HA or 3) left undisturbed (control). We report that dual immunohistochemical staining for c-Fos and CTb revealed an increase in the percentage of c-Fos-immunopositive basolateral amygdaloid complex-projecting neurons in open-field-exposed rats compared with HA and control rats in the ipsilateral CA1 region of the ventral hippocampus, subiculum and lateral entorhinal cortex. These data are consistent with the hypothesis that exposure to the open-field arena activates an anxiety-related neuronal system with convergent input to the basolateral amygdaloid complex.
焦虑状态及与焦虑相关的行为似乎受包括基底外侧杏仁核在内的一个分布广泛且高度相互连接的脑结构系统调节。我们之前的研究表明，与对照组相比，将大鼠置于高光和低光条件下的旷场中，基底外侧杏仁核前核（BLA）中的c-Fos表达会显著增加。然而，旷场暴露对BLA中c-Fos表达产生解剖学特异性影响的神经机制尚不清楚，不过这可能反映了杏仁核该区域特定传入输入的激活。为了确定介导大鼠焦虑诱导的基底外侧杏仁复合体激活的候选脑区，我们使用霍乱毒素B亚基（CTb）作为逆行示踪剂来识别向该区域有直接传入投射的神经元，并结合c-Fos免疫染色来识别在低光（8 - 13勒克斯）条件下对暴露于旷场环境（大鼠的一种致焦虑刺激）有反应的细胞。成年雄性Wistar大鼠在基底外侧杏仁复合体中单侧微量注射4%溶于磷酸盐缓冲盐水的CTb。CTb注射后，大鼠单独饲养11天，每天处理（HA）2分钟。在测试日，大鼠要么：1）在低光条件（8 - 13勒克斯）下暴露于旷场15分钟（OF）；2）短暂HA，要么3）不做处理（对照）。我们报告，与HA组和对照组大鼠相比，在腹侧海马、下托和外侧内嗅皮质的同侧CA1区，对旷场暴露大鼠中c-Fos免疫阳性的基底外侧杏仁复合体投射神经元的百分比增加。这些数据与以下假设一致，即暴露于旷场环境会激活一个向基底外侧杏仁复合体有汇聚输入的与焦虑相关的神经元系统。
