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，主要是在脑桥核中。当反复服用时，恒定的精神兴奋剂剂量会产生越来越多的行为反应-称为精神兴奋剂致敏。这种药物依赖性的动物模型是由腹侧被盖区的多巴胺神经元细胞体和它们在丘脑核中的突触水平上的神经可塑性变化介导的。这些变化需要突触传递。最近，这个实验室有了惊人的观察，多巴胺神经元共释放谷氨酸。如果是这样的话，多巴胺神经元的多巴胺能突触可能在致敏中起重要作用。为了测试这一点，在本实验室中产生的具有荧光多巴胺神经元的小鼠将被用于检查单个多巴胺神经元的多巴胺能突触末梢之间的关系，并评估作为致敏基础的多巴胺能突触的可塑性能力。为了研究谷氨酸能共传递在行为动物中的作用，人们制造了另一种缺乏谷氨酸胺酶的小鼠品系，这种酶主要负责神经递质谷氨酸的产生。确认转氨酶重要性的初步结果将被扩展到明确测试。有趣的是，谷氨酰胺酶杂合子小鼠似乎已经处于致敏状态，因为它们对兴奋剂表现出过度反应。使用组织特异性拯救和删除的方法，最终的目的是确定敏化表型的关键神经递质回路。最后，将在多巴胺神经元中缺乏转氨酶的小鼠中测试多巴胺能共传递在致敏发展中的作用。这一综合方法应有助于阐明致敏作用的关键神经递质回路，并为药理学减少致敏作用和药物依赖性提供新的靶点。

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.