Rebec G V
Department of Psychology, Indiana University, Bloomington 47405-1301, USA.
Alcohol Clin Exp Res. 1998 Feb;22(1):32-40. doi: 10.1111/j.1530-0277.1998.tb03614.x.
Although ample evidence implicates the dopamine (DA) projection to the neostriatum and nucleus accumbens in motor and motivational processes, relatively little information is available on how DA alters neostriatal or accumbal functions under naturally occurring behavioral conditions. Further insight into neuron-behavior relationships can be achieved with the application of single-unit recording techniques, including iontophoresis and fast-scan cyclic voltammetry (FSCV), to awake, unrestrained animals. Single-unit recording has revealed that amphetamine, a widely abused psychomotor stimulant, activates motor-, but inhibits nonmotor-related neurons in neostriatum and nucleus accumbens. Although either response can be blocked by DA receptor antagonists, the amphetamine-induced activation also depends on an intact corticostriatal system, suggesting a role for glutamate (GLU). Both neostriatal and accumbal neurons are sensitive to iontophoretic application of either DA or GLU, but when applied during low-dose application of DA, the GLU signal is enhanced relative to background activity. In effect, DA appears to modulate GLU by strengthening the GLU signal-to-noise ratio. To assess DA release under behaviorally relevant conditions, FSCV has been used to obtain real-time measurements of DA efflux in a free-choice novelty test. DA efflux increased only during the brief period of entry into novelty, and the increase was confined to accumbal shell and the shell-core transition zone, the so-called shore. Neither accumbal core nor the overlying neostriatum showed a novelty-related DA change. Thus, DA release during behavior is not uniform and in the case of novelty appears targeted to the limbic-related area of accumbal shell. Further application of these and other in vivo technologies to ambulant animals is required to identify the complex mechanisms underlying both the release of DA and its effect on neostriatal and accumbal neurons during behavior.
尽管有充分证据表明多巴胺（DA）投射到新纹状体和伏隔核参与运动和动机过程，但关于在自然行为条件下DA如何改变新纹状体或伏隔核功能的信息相对较少。通过将包括离子电渗疗法和快速扫描循环伏安法（FSCV）在内的单单元记录技术应用于清醒、不受束缚的动物，可以进一步深入了解神经元与行为之间的关系。单单元记录显示，苯丙胺是一种广泛滥用的精神运动兴奋剂，它能激活新纹状体和伏隔核中的运动相关神经元，但抑制非运动相关神经元。尽管这两种反应都可被DA受体拮抗剂阻断，但苯丙胺诱导的激活也依赖于完整的皮质纹状体系统，提示谷氨酸（GLU）发挥了作用。新纹状体和伏隔核神经元对DA或GLU的离子电渗应用均敏感，但在低剂量DA应用期间施加GLU时，GLU信号相对于背景活动增强。实际上，DA似乎通过增强GLU的信噪比来调节GLU。为了评估行为相关条件下的DA释放，FSCV已被用于在自由选择新奇性测试中实时测量DA外流。DA外流仅在进入新奇环境的短暂期间增加，且增加局限于伏隔核壳及壳-核过渡区，即所谓的边缘区。伏隔核核心及上方的新纹状体均未显示与新奇性相关的DA变化。因此，行为期间的DA释放并不均匀，在新奇性情况下，DA释放似乎靶向伏隔核壳的边缘相关区域。需要进一步将这些及其他体内技术应用于活动的动物，以确定行为期间DA释放及其对新纹状体和伏隔核神经元影响的复杂机制。
