Genetic Animal Models for the Study of Serotonin

5-羟色胺神经递质系统及其关键成分之一，5-羟色胺转运体（SERT），是该项目的主要目标。临床科学实验室（LCS）中SERT敲除小鼠的开发为研究SERT和5-羟色胺受体提供了一种新的活体工具，这些受体是世界上使用的最多的神经精神药物的靶分子。30-此外，在5-羟色胺敲除小鼠中还发现了神经化学、行为和其他表型变化。由此产生的数据有助于指导LCS和其他实验室研究最近在人类SERT基因中发现的多功能变体。 我们研究的广泛目标是更好地了解5-羟色胺神经递质系统及其对生理，行为和人类疾病，特别是神经精神疾病的贡献。5-羟色胺与几乎所有已知的生理功能有关。5-羟色胺转运蛋白（SERT）在5-羟色胺释放后将其重新结合，从而终止5-羟色胺在其受体上的作用。 为了更好地了解5-羟色胺的功能，我们建立了一个小鼠模型，该模型要么缺乏5-羟色胺转运蛋白，要么5-羟色胺转运蛋白表达减少50%。这些SERT -/-和+/-小鼠的细胞外液5-羟色胺（5-HT）浓度呈基因比例增加。也就是说，9-和5倍分别超过+/+小鼠，SERT缺乏自受孕以来。同时，SERT -/-小鼠细胞内可释放的5-HT不足50%。这些小鼠在第IV层皮质桶区也有组织学异常，在过去的一年中，使用葡萄糖利用技术测量显示，这些组织学异常导致对晶须刺激的反应的功能障碍。 在焦虑模型中，SERT缺陷小鼠表现出明显更大的焦虑样行为。类似地，这些小鼠响应于轻微的应激刺激（例如处理和盐水注射）具有显著更大的HPA和交感肾上腺系统激活，具有高血浆ACTH和肾上腺素增加，以及垂体和肾上腺激素更显著的减少。通过5-羟色胺1A受体拮抗剂治疗，焦虑行为恢复到接近正常水平。 这些异常的焦虑反应没有改变的5-HT 1A受体的数量，通过重组腺病毒含有1A序列的下丘脑，虽然异常的应激反应得到纠正。由于5-羟色胺对神经元细胞具有营养作用，我们正在研究5-羟色胺转运蛋白和某些神经营养因子如BDNF对神经元功能、存活和发育的作用。我们已经成功地开发了SERT x BDNF双敲除小鼠模型，以进一步研究5-羟色胺转运体和BDNF在神经系统发育中的作用，因为人类遗传研究分别涉及情感和其他神经精神障碍的发展中的两个基因。在过去的一年里，我们报道了缺乏一个BDNF等位基因的SERT -/-小鼠有更明显的细胞内单胺缺乏，也有更大的应激反应异常和焦虑相关行为。

The serotonin neurotransmitter system and one of its key components, the serotonin transporter (SERT), is the primary target of this project. The development of the SERT knockout mouse in the Laboratory of Clinical Science (LCS) provided a new living tool to study SERT and serotonin receptors, the target molecules for the largest numbers of neuropsychiatric drugs used in the world. 30-plus neurochemical, behavioral and other phenotypic changes have been discovered in the serotonin knockout mouse. The resulting data is helping to guide the LCS and other laboratories in investigations of the multiple functional variants recently discovered in the human SERT gene. The broad goal of our studies is a better understanding of the serotonin neurotransmitter system and its contributions to physiology, behavior and human disorders, especially neuropsychiatric disorders. Serotonin has been implicated in almost every physiological function known. The serotonin transporter (SERT) recycles serotonin after its release, thereby terminating the action of serotonin at its receptors. In our attempt to better understand serotonin's function, we have generated a mouse model which either lacks the serotonin transporter or has a 50% reduction in serotonin transporter expression. These SERT -/- and +/- mice have gene-proportionate increases in extracellular fluid serotonin (5-HT) concentrations. i.e., 9- and 5-fold excesses respectively over +/+ mice, with the SERT deficiency present since conception. At the same time, the SERT -/- mice have a 50% deficit of intracellular, releasable 5-HT. These mice also have histological abnormalities in layer IV cortex barrel fields which were demonstrated in the past year to lead to functional impairment in responses to whisker stimulation as measured using glucose utilization techniques. In models of anxiety, the SERT deficient mice exhibit markedly greater anxiety-like behaviors. Similarly, these mice have substantially greater activation of the HPA and sympathoadrenal systems in responses to minor stressful stimuli such as handling and saline injections, with high plasma ACTH and epinephrine increases, and more marked reductions in pituitary and adrenal gland hormones. The anxiety behaviors are restored to near normal levels by treatment with a serotonin 1A receptor antagonist. These abnormal anxiety responses were unchanged by restorations of 5-HT1A receptor number via recombinant adenovirus containing 1A sequences in the hypothalamus, although the abnormal stress responses were corrected. As serotonin has a trophic effect on neuronal cells, we are investigating the role of the serotonin transporter and certain neurotrophic factors such as BDNF on neuronal function, survival, and development. We have successfully developed a SERT x BDNF double knockout mouse model to further investigate the role of the serotonin transporter and BDNF in the developing nervous system, as human genetic studies have separately implicated both genes in the development of affective and other neuropsychiatric disorders. In the past year, we reported that SERT -/- mice who lacked one BDNF allele had more marked intracellular monoamine deficiencies and also had greater stress-response abnormalities and anxiety-related behaviors.