Control of Fear/Defensive Behavior by Brain Derived Neurotrophic Factor

脑源性神经营养因子控制恐惧/防御行为

• 批准号: 7969396
• 负责人: Alexei Morozov
• 金额: $ 100.9万
• 依托单位: NATIONAL INSTITUTE OF MENTAL HEALTH
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7969396
• 关键词: Address; Affect; Aggressive behavior; Agonist; Alcoholism; Amygdaloid structure; Area; Behavior; Brain; Brain-Derived Neurotrophic Factor; Carbachol; Cells; Citalopram; Cognitive; Dementia; Elderly; Emotional; Equilibrium; Frequencies; Fright; Future; Generations; Genetic; Goals; Green Fluorescent Proteins; Hippocampus (Brain); Human; Hypothalamic structure; Interneurons; Investigation; Knock-out; Knockout Mice; Laboratories; Lead; Location; Measures; Mental disorders; Microdialysis; Modeling; Molecular; Mus; Neurons; Pattern; Physiological; Property; Role; Selective Serotonin Reuptake Inhibitor; Serotonin; Serotonin Receptors 5-HT-3; Slice; Societies; Structure; System; Therapeutic Intervention; Transgenic Mice; Work; cost; extracellular; knockout animal; midbrain central gray substance; promoter; reuptake

Multiple studies suggest that interactions between the higher brain structures, such as cortex and hippocampus, and so called defensive circuitry, which include amygdala, hypothalamus and periaqueductal grey, modulate fear/defensive behaviors. Moreover, changes in such interaction may lead to mental illness. We have previously found that mice with the conditional knockout (KO) of Brain Derived Neurotrophic Factor (BDNF) restricted to the hippocampal area CA3 are more aggressive than their wild type (WT) counterparts. During the past fiscal year we pursued two aims. 1) Identification of mechanisms responsible for previously found changes in serotonergic system of BDNF KO mice. 2) Investigation of physiological role of the hippocampal serotonin receptor 3 (5-HTr3), which has been found to enhance aggression. To address the first aim we employed microdialysis/HPLC system for measuring levels of extracellular serotonin in various locations throughout the hippocampus. This work revealed that the decrease in 5-HT concentration occurs in the vicinity of the area CA3, but not in the locations that are far from this area. This finding indicated that BDNF effect on 5-HT level is localized even within the hippocampus. To examine local mechanism that control levels of 5-HT we used reverse microdilaysis with serotonin reuptake inhibitor citalopram, which increases level of 5-HT by suppressing 5-HT reuptake, and KCl, which increases level of 5-HT by triggering activity-dependent release of 5-HT from serotonergic terminals. The analysis revealed that gross 5-HT transporter activity and vesicular content of serotonergic terminals are not altered in KO animals. It suggests that BDNF modulates balance between 5-HT release and reuptake at the basal state, but does not alter release or reuptake capacity of serotonergic terminals. To investigate physiological role of 5-HTr3 in the hippocampus we combined genetic and pharmacological approaches to selectively modulate 5-HTr3 with specific agonist and antagonist and to record from the interneuronal subpopulation that express 5-HTr3. For the latter, we obtained transgenic mice where green fluorescent protein (GFP) is expressed under the control of 5-HTr3 promoter and allows recording from cells with 5-HTr3. One of the major physiological properties of the hippocampus is generation of oscillatory activity at certain frequencies. Oscillations at gamma frequency have been postulated to be important for both cognitive and emotional behaviors and can be modeled in the hippocampal slice. We reproduced this model in our laboratory and examined how 5-HTr3 affects gamma oscillations induced by carbachol. We discovered that 5-HTr3 agonist suppresses gamma oscillations and are trying to determine underlying mechanisms at the level of local hippocampal circuit. Preliminary finding suggest that a5-HTr3 alters afterhyperpolarization of 5-HTr3 expressing interneurons, which alters their firing patterns leading to the interference with gamma oscillations. Our future goals are to understand how oscillatory activity of hippocampus may relate to aggression and whether 5-HTr3 modulates aggression by changing hippocampal oscillations.

多项研究表明，高级大脑结构（例如皮层和海马体）与所谓的防御回路（包括杏仁核、下丘脑和导水管周围灰质）之间的相互作用可以调节恐惧/防御行为。此外，这种互动的改变可能会导致精神疾病。 我们之前发现，海马区 CA3 脑源性神经营养因子 (BDNF) 条件性敲除 (KO) 的小鼠比野生型 (WT) 小鼠更具攻击性。在过去的财政年度中，我们追求两个目标。 1) 鉴定先前发现的 BDNF KO 小鼠血清素能系统变化的机制。 2) 研究海马血清素受体 3 (5-HTr3) 的生理作用，发现它可以增强攻击性。 为了实现第一个目标，我们采用微透析/高效液相色谱系统来测量整个海马体不同位置的细胞外血清素水平。这项工作表明，5-HT 浓度的降低发生在 CA3 区域附近，但远离该区域的位置则不然。这一发现表明 BDNF 对 5-HT 水平的影响甚至局限于海马体内。为了检查控制 5-HT 水平的局部机制，我们使用血清素再摄取抑制剂西酞普兰和 KCl 进行反向微透析，西酞普兰通过抑制 5-HT 再摄取来增加 5-HT 水平，而 KCl 通过触发血清素能末端的 5-HT 活性依赖性释放来增加 5-HT 水平。分析显示，KO 动物中 5-HT 转运蛋白总活性和血清素末端的囊泡含量没有改变。这表明 BDNF 在基础状态下调节 5-HT 释放和再摄取之间的平衡，但不改变血清素能末端的释放或再摄取能力。 为了研究 5-HTr3 在海马中的生理作用，我们结合遗传学和药理学方法，用特定激动剂和拮抗剂选择性调节 5-HTr3，并记录表达 5-HTr3 的中间神经元亚群。对于后者，我们获得了转基因小鼠，其中绿色荧光蛋白 (GFP) 在 5-HTr3 启动子的控制下表达，并允许从具有 5-HTr3 的细胞进行记录。 海马体的主要生理特性之一是产生特定频率的振荡活动。伽马频率的振荡被认为对认知和情绪行为都很重要，并且可以在海马切片中建模。我们在实验室重现了这个模型，并研究了 5-HTr3 如何影响卡巴胆碱诱导的伽马振荡。我们发现 5-HTr3 激动剂可抑制伽马振荡，并试图确定局部海马回路水平的潜在机制。初步发现表明，a5-HTr3 改变表达 5-HTr3 的中间神经元的后超极化，从而改变其放电模式，从而干扰伽马振荡。 我们未来的目标是了解海马体的振荡活动如何与攻击性相关，以及 5-HTr3 是否通过改变海马体的振荡来调节攻击性。