Transgenic analysis of glutamate in sensitization

描述（由申请人提供）：精神兴奋剂通过增加突触多巴胺水平起作用，主要在伏隔核。当反复服用时，持续的精神兴奋剂剂量会产生越来越多的行为反应——被称为精神兴奋剂致敏。该药物依赖动物模型是由腹侧被盖区多巴胺神经元胞体及其伏隔核突触水平的神经可塑性改变介导的。这些变化需要谷氨酸能突触传递。最近，这个实验室做出了惊人的观察，多巴胺神经元共同释放谷氨酸。如果是这样，多巴胺神经元的谷氨酸能突触可能在致敏过程中起重要作用。为了验证这一点，本实验室将使用荧光多巴胺神经元生成的小鼠来检查单个多巴胺神经元的多巴胺能和谷氨酸能末端之间的关系，并评估谷氨酸能突触的可塑性能力，作为致敏的基础。为了研究谷氨酸能在动物行为中共同传递的作用，研究人员制造了另一种缺乏谷氨酰胺酶的小鼠，谷氨酰胺酶主要负责神经递质谷氨酸的产生。证实谷氨酰胺酶的重要性的初步结果将进一步扩大，以确定这一点。有趣的是，谷氨酰胺酶杂合的小鼠似乎已经处于敏感状态，因为它们对兴奋剂表现出夸张的反应。使用组织特异性修复和删除方法，最终目的是确定致敏表型背后的关键谷氨酸能回路。最后，将在多巴胺神经元缺乏谷氨酰胺酶的小鼠中测试多巴胺神经元的谷氨酸能共传递在致敏发展中的作用。这种综合方法将有助于阐明致敏的关键谷氨酸能回路，并为减少致敏和药物依赖提供新的靶点。

DESCRIPTION (provided by applicant): Psychostimulants act by increasing synaptic dopamine levels, principally in the nucleus accumbens. When taken repeatedly, constant psychostimulant doses produce an increasing behavioral response - known as psychostimulant sensitization. This animal model of drug dependence is mediated by neuroplastic changes both at the level of the dopamine neuron cell bodies in the ventral tegmental area and a their synapses in the nucleus accumbens. These changes require glutamatergic synaptic transmission. Recently, this laboratory has made the striking observation that dopamine neurons corelease glutamate. If so, glutamatergic synapses of dopamine neurons are likely to be important in sensitization. To test this, mice generated in this laboratory with fluorescent dopamine neurons will be used to examine the relationship between the dopaminergic ami glutamatergic terminals of single dopamine neurons and to assess the plastic capabilities of the glutamatergic synapses as a basis for sensitization. To address the role of the glutamatergic cotransmission in the behaving animal, another line of mice have been made that lack glutaminase - the enzyme principally responsible for Ihe production of neurotransmitter glutamate. Preliminary results confirming the importance of glutaminase will be extended to test this definitively. Interestingly, mice heterozygous for glutaminase appear to be already in a sensitized state, as they show an exaggerated response to stimulants. Using tissue-specific rescue and deletion approaches, the final aim is to identify the crucial glutamatergic circuits underlying the sensitized phenotype. Finally, the role of glutamatergic cotransmission by dopamine neurons in the development of sensitization will be tested in mice lacking glutaminase in their dopamine neurons. This integrated approach should help to elucidate the crucial glutamatergic circuits underlying sensitization, and offer new targets lor the pharmacological reduction of sensitization and thus of drug dependence.