Transgenic analysis of glutamate in sensitization

描述(申请人提供)：精神刺激剂通过增加突触多巴胺水平发挥作用，主要是在伏隔核内。当反复服用心理刺激剂时，持续剂量的心理刺激剂会产生越来越大的行为反应--称为心理刺激剂敏化。这种药物依赖的动物模型是由腹侧被盖区多巴胺神经元胞体及其伏核突触水平的神经可塑性变化所介导的。这些变化需要谷氨酸能突触传递。最近，该实验室进行了惊人的观察，发现多巴胺神经元协同释放谷氨酸。如果是这样的话，多巴胺神经元的谷氨酸能突触很可能在敏化过程中起重要作用。为了测试这一点，在这个实验室中产生的带有荧光多巴胺神经元的小鼠将被用来检查单个多巴胺神经元的多巴胺能氨基谷氨酸能终末之间的关系，并评估作为敏化基础的谷氨酸能突触的可塑性。为了解决谷氨酸能共传递在行为动物中的作用，另一种缺乏谷氨酰胺酶的小鼠被制造出来。谷氨酰胺酶是一种主要负责产生神经递质谷氨酸的酶。确认谷氨酰胺酶重要性的初步结果将扩大到最终检验这一点。有趣的是，谷氨酰胺酶杂合子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大的反应。利用组织特异性的挽救和缺失方法，最终目的是确定致敏表型背后的关键谷氨酸能回路。最后，将在多巴胺神经元中缺乏谷氨酰胺酶的小鼠身上测试多巴胺神经元谷氨酸能共传递在致敏发展中的作用。这种综合的方法应该有助于阐明致敏的关键谷氨酸能回路，并为药物减敏从而减少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.