Direct measurements of neurotransmitter concentrations in vivo

描述（由申请人提供）：当两个神经元相遇时，它们可以形成突触，并且可以发生化学通讯。这是大脑的功能单元，在这个层面上，变化等同于学习。拟议的研究将开发并使用电化学方法来测量体内容易氧化的神经递质的绝对浓度-这是目前方法无法实现的。神经递质细胞外浓度的快速变化可由相性神经元放电引起。由于这个原因，化学传感器应该能够在很宽的时间尺度范围内工作。一种理想的神经递质检测传感器具有高灵敏度，能够区分化合物，并具有快速的响应时间。电化学方法为容易氧化的神经递质提供了一种方法，通过在神经递质释放位点旁边使用电极来实现这一目标。背景减去循环伏安法是一种广泛使用的方法，能够在亚秒时间尺度上测量神经递质浓度的变化。这种方法已被证明是测量浓度的一种有价值的工具；然而，它不能测量神经递质的绝对浓度。绝对浓度是至关重要的，因为它影响受体的占用，并可以改变释放的神经递质对受体的作用。一种新的方法来测量绝对浓度的易氧化的神经递质在一秒的时间尺度将被开发。这种方法依赖于这些分子在传感表面的吸附。背景相减循环伏安法通常在动力学受限的条件下进行。在本实验中，我们允许通过改变检测参数来改变吸附到表面的量。通过让系统接近平衡，然后把它推得更远，就可以测量出存在的神经递质的绝对浓度。该方法将通过使用表征良好的药物进行验证。可卡因和利他林（一种精神兴奋剂药物）对大鼠纹状体中多巴胺绝对浓度的影响将被确定。哌醋甲酯被批准用于治疗注意缺陷多动障碍、体位性心动过速综合征和嗜睡症。像其他兴奋剂一样，哌醋甲酯会增加大脑中多巴胺的浓度；然而，哌甲酯如何改变这些浓度还没有精确的时间分辨率测量。

DESCRIPTION (provided by applicant): Where two neurons meet they can form a synapse and chemical communication can occur. This is the functional unit of the brain, and it is at this level where changes equate to learning. The proposed research will develop and then use electrochemical methods to measure the absolute concentrations of easily oxidized neurotransmitters in vivo - something not possible with current methodology. Fast changes in the extracellular concentration of neurotransmitters can arise from phasic neuronal firing. For this reason, chemical sensors should be able to operate on a wide range of time scales. An ideal sensor for the detection of neurotransmitters has high sensitivity, can distinguish between compounds, and has a fast response time. Electrochemical approaches offer a way to accomplish this for easily oxidized neurotransmitters by using an electrode next to sites where the neurotransmitter is released. Background-subtracted cyclic voltammetry, one widely used method is capable of measuring changes in neurotransmitter concentrations on a sub-second timescale. This methodology has proved to be a valuable tool to measure the concentrations; however, it cannot measure the absolute concentrations of neurotransmitters. The absolute concentration is of critical importance as it affects the receptor occupancy and can change the effect of released neurotransmitters on the receptors. A novel method to measure the absolute concentrations of easily oxidizable neurotransmitters on a single-second timescale will be developed. This method relies on the adsorption of these molecules to the sensing surface. Background-subtracted cyclic voltammetry is typically performed in a kinetically limited regime. In this experiment, we allow the amount adsorbed to the surface to vary by changing detection parameters. By allowing the system to come close to equilibrium, and then pushing it farther away, the absolute concentration of neurotransmitter present can be measured. The method will be validated by using well-characterized drugs. The effects of cocaine and methylphenidate (Ritalin), a psychostimulant drug on the absolute dopamine concentration in the rat striatum will be determined. Methylphenidate is approved for the treatment of attention-deficit hyperactivity disorder, postural orthostatic tachycardia syndrome, and narcolepsy. Methylphenidate, like other stimulants, increases the concentration of dopamine in the brain; however how methylphenidate changes these concentrations has not been measured with exquisite temporal resolution.