Mechanisms Regulating Serotonin Clearance In Vivo: Studies Using KO Mice

体内血清素清除率的调节机制：使用 KO 小鼠进行的研究

• 批准号: 7468343
• 负责人: LYNETTE C DAWS
• 金额: $ 32.85万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-12-11 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7468343
• 关键词: Affect; Affective; Affinity; Alcoholism; Alcohols; Alleles; Antidepressive Agents; Behavior; Brain region; Cations; Clinical; Data; Disease; Dopamine; Drug Delivery Systems; Drug abuse; Drug effect disorder; Effectiveness; Ethanol; Extracellular Fluid; Genes; Genetic Polymorphism; Genotype; Heterozygote; Hippocampus (Brain); Human; Individual; Knockout Mice; Lead; Measures; Mental Depression; Mental disorders; Mus; Mutant Strains Mice; Neurons; Pharmaceutical Preparations; Play; Proline; Promoter Regions; Resistance; Role; Selective Serotonin Reuptake Inhibitor; Serotonin; Site; Synapses; Treatment Efficacy; Up-Regulation; Variant; Wild Type Mouse; Work; alcohol abuse therapy; drug of abuse; ecstasy; extracellular; in vivo; interest; mutant; neurochemistry; neurotransmission; noradrenaline transporter; novel; null mutation; pre-clinical; proline permease; serotonin transporter; uptake

DESCRIPTION (provided by applicant): The serotonin transporter (5-HTT) regulates serotonergic neurotransmission by high affinity uptake of released serotonin. It is a key site of action for many psychotherapeutic and addictive drugs. The level of 5-HTT expression varies in humans according to whether an individual carries the short (s) variant of the 5-HTT promoter region polymorphism (5-HTTLPR). Carriers of the s allele express ~50% fewer 5-HTTs than those homozygous for the long (/) allele. Carriers of the s allele appear to be more prone to a variety of psychiatric disorders, including depression and drug abuse, and are often resistant to treatment with selective serotonin reuptake inhibitors (SSRIs) compared to individuals homozygous for the / allele. To study the neurochemical underpinnings of the relationship between 5-HTT genotype and drug effect, we have made use of mice with a null mutation of the 5-HTT. Heterozygote 5-HTT mutants resemble carriers of the s allele in that they express 50% fewer 5-HTTs and clear serotonin from extracellular fluid more slowly than wild-type mice. The null mutants lack 5-HTTs. One of our most intriguing findings is that 5-HTT mutant mice are more sensitive to the serotonin clearance inhibiting effect of "Ecstasy" (MDMA) and alcohol where greatest inhibition of serotonin clearance occurs in null mutants. Thus, these drugs inhibit serotonin clearance but via a 5-HTT independent mechanism. Importantly, this mechanism has presumably undergone compensatory upregulation in 5-HTT mutants. The studies proposed here seek to identify these alternative mechanisms for serotonin transport. It is known that the dopamine and norepinephrine transporters take up serotonin, but preliminary data indicate that at least in the CA3 region of hippocampus these transporters do not play a significant role in serotonin clearance in 5-HTT mutant mice. By contrast, blockers of the organic cation (OCT) and proline (PROT) transporters profoundly inhibit serotonin clearance in 5-HTT mutant mice. Here we will determine the relationship between genetically defined deficiencies in 5-HTT expression and (1) OCT and PROT expression, (2) OCT and PROT function and (3) behavior to assess changes in effectiveness of SSRIs and blockers of the OCT and PROT in preclinical measures for antidepressant efficacy and treatment of alcoholism. We will also investigate OCT and PROT as sites of action for antidepressant and abused drugs and how their efficacy varies with 5-HTT genotype. In addition to increasing our fundamental understanding of serotonergic neurotransmission, these studies may lead to novel treatments for affective and addictive disorders that are better tailored to the individual. The clinical implications for upregulation of alternative mechanisms for serotonin uptake when 5-HTT expression is compromised are far reaching. That is, drugs targeted at OCTs or PROT may represent first line or adjunctive therapies for individuals who do not respond well to treatment with SSRIs.

描述(申请人提供)：5-羟色胺转运体(5-HTT)通过高亲和力摄取释放的5-羟色胺来调节5-羟色胺能神经传递。它是许多心理治疗和成瘾药物的关键作用场所。在人类中，5-HTT的表达水平取决于个人是否携带5-HTT启动子区域多态的短(S)变体(5-HTTLPR)。携带S等位基因的携带者比携带Long(/)等位基因的携带者表达的5-HTTS减少约50%。S等位基因携带者似乎更容易患上各种精神疾病，包括抑郁和药物滥用，而且与该等位基因纯合子相比，他们往往对选择性5-羟色胺再摄取抑制剂(SSRI)的治疗产生抵抗力。为了研究5-HTT基因型与药物效应之间关系的神经化学基础，我们利用了5-HTT零突变的小鼠。杂合子5-HTT突变体与S等位基因携带者的相似之处在于，它们比野生型小鼠表达5-HTT和细胞外液中透明的5-羟色胺的速度要慢50%。零突变体缺少5-HTTS。我们最有趣的发现之一是，5-HTT突变小鼠对摇头丸(MDMA)和酒精的5-羟色胺清除抑制作用更敏感，其中对5-羟色胺清除的抑制最大的是零突变。因此，这些药物抑制5-羟色胺清除，但通过5-HTT独立的机制。重要的是，这一机制可能在5-HTT突变体中经历了代偿性上调。这里提出的研究试图确定5-羟色胺转运的这些替代机制。已知多巴胺和去甲肾上腺素转运体摄取5-羟色胺，但初步数据表明，至少在海马区CA3区，这些转运体在5-HTT突变小鼠清除5-羟色胺的过程中不起重要作用。相比之下，有机阳离子(OCT)和脯氨酸(PROT)转运体的阻断剂可以深刻地抑制5-HTT突变小鼠的5-羟色胺清除。在这里，我们将确定基因定义的5-HTT表达缺陷与(1)OCT和Prot表达，(2)OCT和Prot功能，以及(3)行为之间的关系，以评估SSRIs和OCT和Prot阻滞剂在抗抑郁疗效和治疗酒精中毒的临床前措施中的有效性变化。我们还将研究OCT和PROT作为抗抑郁药物和滥用药物的作用部位，以及它们的疗效如何随5-HTT基因的不同而变化。除了增加我们对5-羟色胺能神经传递的基本了解外，这些研究还可能导致针对情感性和成瘾障碍的新疗法，这些疗法更适合个人。当5-HTT表达受损时上调5-羟色胺摄取的替代机制的临床意义是深远的。也就是说，针对OCT或PROT的药物可能是对SSRIs治疗反应不佳的个人的一线或辅助治疗。