生物谷：心患有焦虑症的人常常将不明确的环境视作威胁，最近，来自欧洲分子生物学实验室（EMBL）的科学家发现了老鼠中焦虑的分子学基础。在最新的Nature Neuroscience中，他们报导了一种血清胺（serotonin）受体和大脑海马体中一种神经回路在产生这种恐惧反应过程中起到了关键作用。??
老鼠能记住某些暗示，例如在一个声音之后常常跟着电击，因此它们会将这两者联系起来，即使在没有电击的时候，老鼠听到声音也会害怕。但在现实生活中情况没有这么明显。正常老鼠对于模糊暗示的恐惧程度要小于明确的威胁暗示。??
由EMBL的Cornelius Gross领导的研究小组发现对于模糊的刺激反应需要血清胺的一种特殊受体分子，血清胺是很多大脑细胞交流的信号。缺少血清胺受体1A的老鼠对于处理模糊刺激存在问题，因此对它们会做出完全的威胁反应。其中原因在于大脑细胞错误的联系。血清胺信号在大脑发育中非常重要，如果没有1A，大脑联系会存在缺陷，并且将影响老鼠的行为。??
利用一种关闭特定大脑细胞神经活动的技术，Gross和同事发现海马体的一个特殊部位对于正确处理模糊刺激很重要。海马体是负责学习和记忆的区域，但是研究显示它在评估信息方面也起着重要作用。??
以上对于血清胺受体1A和海马体在恐惧行为中作用的发现将有助于了解焦虑的神经基础，并带来新的治疗手段。（引自教育部科技发展中）
原始出处:
Nature Neuroscience
Published online: 3 June 2007; | doi:10.1038/nn1919
Suppression of conditioning to ambiguous cues by pharmacogenetic inhibition of the dentate gyrus
Theodoros Tsetsenis1, Xiao-Hong Ma2, Luisa Lo Iacono1, Sheryl G Beck2 & Cornelius Gross1
1 European Molecular Biology Laboratory (EMBL), Mouse Biology Unit, Via Ramarini 32, 00015 Monterotondo, Italy.
2 Children's Hospital of Philadelphia, 3615 Civic Center Blvd., Philadelphia, Pennsylvania 19104, USA.
Serotonin receptor 1A knockout (Htr1aKO) mice show increased anxiety-related behavior in tests measuring innate avoidance. Here we demonstrate that Htr1aKO mice show enhanced fear conditioning to ambiguous conditioned stimuli, a hallmark of human anxiety. To examine the involvement of specific forebrain circuits in this phenotype, we developed a pharmacogenetic technique for the rapid tissue- and cell type–specific silencing of neural activity in vivo. Inhibition of neurons in the central nucleus of the amygdala suppressed conditioned responses to both ambiguous and nonambiguous cues. In contrast, inhibition of hippocampal dentate gyrus granule cells selectively suppressed conditioned responses to ambiguous cues and reversed the knockout phenotype. These data demonstrate that Htr1aKO mice have a bias in the processing of threatening cues that is moderated by hippocampal mossy-fiber circuits, and suggest that the hippocampus is important in the response to ambiguous aversive stimuli
