Borland Laura M, Shi Guoyue, Yang Hua, Michael Adrian C
Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, USA.
J Neurosci Methods. 2005 Aug 15;146(2):149-58. doi: 10.1016/j.jneumeth.2005.02.002. Epub 2005 Mar 5.
Establishing in vivo microdialysis methods for the quantitative determination of dopamine concentrations in the extracellular space of the brain is an important yet challenging objective. The source of the challenge is the difficulty in directly measuring the microdialysis recovery of dopamine during an in vivo experiment. The recovery value is needed for quantitative microdialysis, regardless of whether conventional or no-net-flux methods are used. Numerical models of microdialysis that incorporate both diffusion and active transport processes suggest that dopamine recovery is strongly affected by processes occurring in the tissue closest to the probe. Some evidence suggests that the tissue adjacent to the probe becomes disrupted during probe implantation. Hence, the objective of the present study was to further identify whether the tissue adjacent to the probe is disrupted and, if so, whether that disruption might affect dopamine recovery. The experiments were conducted with microdialysis probes implanted acutely in the striatum of rats anesthetized with chloral hydrate. Carbon fiber voltammetric microelectrodes were used to monitor extracellular dopamine at three sites near the probes; immediately adjacent to the probe, 220-250 microm from the probe, and 1 mm from the probe. Probes were lowered slowly over a 30 min period, so that dialysate dopamine levels were stable, in the low nanomolar range, and partially TTX-sensitive by the time experiments began. Starting 2h after probe implantation, dopamine was monitored by fast-scan cyclic voltammetry during electrical stimulation of the medial forebrain bundle and during administration of the dopamine uptake inhibitor, nomifensine. The findings of this study show that a gradient of dopamine release and uptake activity extends at least 220 microm from microdialysis probes implanted acutely in the striatum of the anesthetized rat.
建立用于定量测定脑细胞外空间中多巴胺浓度的体内微透析方法是一个重要但具有挑战性的目标。挑战的来源在于在体内实验期间直接测量多巴胺的微透析回收率存在困难。无论使用传统方法还是无净通量方法，定量微透析都需要回收率值。结合扩散和主动转运过程的微透析数值模型表明，多巴胺回收率受到最靠近探针的组织中发生的过程的强烈影响。一些证据表明，在探针植入过程中，与探针相邻的组织会受到破坏。因此，本研究的目的是进一步确定与探针相邻的组织是否受到破坏，如果是，这种破坏是否可能影响多巴胺回收率。实验使用急性植入水合氯醛麻醉大鼠纹状体的微透析探针进行。碳纤维伏安微电极用于监测探针附近三个位置的细胞外多巴胺；紧邻探针、距离探针220 - 250微米以及距离探针1毫米处。探针在30分钟内缓慢下降，以便在实验开始时透析液多巴胺水平稳定，处于低纳摩尔范围且部分对河豚毒素敏感。在探针植入后2小时开始，在电刺激内侧前脑束期间以及给予多巴胺摄取抑制剂诺米芬辛期间，通过快速扫描循环伏安法监测多巴胺。本研究结果表明，在急性植入麻醉大鼠纹状体的微透析探针周围，多巴胺释放和摄取活性的梯度至少延伸220微米。
