Yang H, Peters J L, Michael A C
Department of Chemistry, University of Pittsburgh, Pennsylvania 15260, USA.
J Neurochem. 1998 Aug;71(2):684-92. doi: 10.1046/j.1471-4159.1998.71020684.x.
Voltammetric microelectrodes and microdialysis probes were used simultaneously to monitor extracellular dopamine in rat striatum during electrical stimulation of the medial forebrain bundle. Microelectrodes were placed far away (1 mm) from, immediately adjacent to, and at the outlet of microdialysis probes. In drug-naive rats, electrical stimulation (45 Hz, 25 s) evoked a robust response at microelectrodes far away from the probes, but there was no response at microelectrodes adjacent to and at the outlet of the probes. After nomifensine administration (20 mg/kg i.p.), stimulation evoked robust responses at all three microelectrode placements. These results demonstrate first that evoked release in tissue adjacent to microdialysis probes is suppressed in comparison with evoked release in tissue far away from the probes and second that equilibration of the dopamine concentration in the extracellular fluid adjacent to and far away from the probes is prevented by the high-affinity dopamine transporter. Hence, models of microdialysis, which assume the properties of tissue to be spatially uniform, require modification to account for the distance that separates viable sites of evoked dopamine release from the probe. We introduce new mass transfer resistance parameters that qualitatively explain the observed effects of uptake inhibition on stimulation responses recorded with microdialysis and voltammetry.
在对内侧前脑束进行电刺激期间，同时使用伏安微电极和微透析探针来监测大鼠纹状体中的细胞外多巴胺。微电极分别放置在距离微透析探针较远（1毫米）、紧邻微透析探针以及微透析探针出口处。在未用药的大鼠中，电刺激（45赫兹，25秒）在远离探针的微电极处引发了强烈反应，但在紧邻探针及探针出口处的微电极上没有反应。给予诺米芬辛（20毫克/千克腹腔注射）后，刺激在所有三个微电极放置位置均引发了强烈反应。这些结果首先表明，与远离探针的组织中的诱发释放相比，微透析探针附近组织中的诱发释放受到抑制；其次表明，高亲和力多巴胺转运体阻止了探针附近和远离探针的细胞外液中多巴胺浓度的平衡。因此，假设组织特性在空间上均匀的微透析模型需要修正，以考虑诱发多巴胺释放的活性位点与探针之间的距离。我们引入了新的传质阻力参数，这些参数定性地解释了摄取抑制对微透析和伏安法记录的刺激反应的观察到的影响。
