Alpha adrenoceptors modulate VTA and PFC in cocaine sensitization

描述（由申请人提供）：可卡因致敏是由随后的可卡因刺激引起的运动刺激作用的进行性和持久性增强。这项工作的目的是阐明在VTA和RFC的α肾上腺素能受体在可卡因致敏的发展和表达中的作用。有三个具体目的：1)评估向VTA或RFC显微注射α -去甲肾上腺素能受体激动剂和拮抗剂是否调节可卡因致敏过程。利用可卡因致敏模型，在vta或-RFC内显微注射选择性α -去甲肾上腺素能受体激动剂和拮抗剂将用于定位介导这些药物药理作用的解剖结构。2)确定行为致敏引起的VTA和RFC α -去甲肾上腺素能受体的变化。我们将使用激动剂刺激的[35S] GTPyS结合作为功能分析，研究可卡因致敏大鼠α -1和α -2肾上腺素能受体介导的G蛋白活化。假设可卡因致敏的发展涉及VTA和RFC区域α -1受体功能敏感性的增加和α -2受体功能敏感性的降低，这将促进可卡因致敏。使用体外受体放射自显影分析，将在每种结构中功能和受体数量/亲和力的变化之间建立相关性。我们还将通过比较停药7天后的动物，评估这些去甲肾上腺素能受体的变化是否在行为致敏的开始或表达中发挥作用。3)确定α -2受体在谷氨酸释放调节中的作用。腹侧被盖区。体外全细胞膜片钳记录将用于研究α -2受体在谷氨酸释放到VTA多巴胺细胞中的调节作用。将评估α -2肾上腺受体激动剂对谷氨酸诱导的兴奋性突触后电流（EPSCs）的影响。配对脉冲比和微型EPSC将被用来证明EPSC的改变局限于突触前末端。假设是突触前α -2受体控制谷氨酸释放到VTA神经元。一种次级假设是，在可卡因致敏大鼠中，α -2诱导的谷氨酸释放抑制减少。在停药期后，α肾上腺素受体调节谷氨酸释放到VTA细胞的变化也将被确定。了解-肾上腺素能受体在可卡因致敏中的调节变化将增加我们对去甲肾上腺素能系统在可卡因成瘾中的作用的认识，并可能为治疗性药物干预提供可能的途径。

DESCRIPTION (provided by applicant): Cocaine sensitization is a progressive and long-lasting enhancement of the motor stimulant effect induced by a subsequent cocaine challenge. The goal of this work is to elucidate the role of alpha adrenergic receptors at the VTA and RFC in the development and expression of cocaine sensitization. There are three specific Aims: 1) Assess whether microinjections of alpha noradrenergic receptor agonists and antagonists into the VTA or RFC modulate the process of cocaine sensitization. Using the model of cocaine sensitization, intra-VTA or -RFC microinjections of selective alpha-noradrenergic receptor agonists and antagonists will be used to localize the anatomical structure mediating the pharmacological actions of these drugs. 2) Identify changes in alpha noradrenergic receptors at the VTA and RFC induced by behavioral sensitization. We will investigate alpha-1 and alpha-2 adrenergic receptor mediated G protein activation in cocaine-sensitized rats using agonist-stimulated [35S] GTPyS binding as a functional assay. The hypothesis is that development of cocaine sensitization involves an increase in alpha-1 and a decrease in alpha-2 receptor functional sensitivity in both VTA and RFC areas, which will promote cocaine sensitization. Correlations will be made between changes in functionality and number/affinities of receptors in each structure using an in vitro receptor autoradiography assay. We will also assess whether changes in these noradrenergic receptors play a role in the initiation or expression of behavioral sensitization by comparing animals after a 7days withdrawal period. 3) Determine the role of alpha-2 receptors in the modulation of glutamate release at .the VTA. In vitro whole cell patch clamp recordings will be employed to study the role of alpha-2 receptors in the modulation of glutamate release onto VTA dopamine cells. The effects of alpha-2 adrenoreceptor agonists on glutamate-induced excitatory postsynaptic currents (EPSCs) will be assessed. Paired-pulse ratios and miniature EPSCs will be employed to provide evidence that the EPSC's alterations are localized at the presynaptic terminal. The hypothesis is that presynaptic alpha-2 receptors control glutamate release onto VTA neurons. A sub-hypothesis is that there is a decreased alpha-2 -induced inhibition of glutamate release in cocaine sensitized rats. Changes in alpha adrenoceptor modulation of glutamate release into VTA cells after a withdrawal period will also be determined. Understanding of alpha adrenoceptor modulatory changes in cocaine sensitization will increase our knowledge of the role of the noradrenergic system in cocaine addiction and might provide possible avenues for therapeutic pharmacological interventions..