Kristensen E W, Bigelow J C, Wightman R M
Department of Chemistry, Indiana University, Bloomington 47405.
Brain Res. 1988 Sep 27;461(1):44-52. doi: 10.1016/0006-8993(88)90723-8.
Overflow of dopamine has been measured with a rapid superfusion apparatus in an attempt to obtain a system in which overflow is a measure of the primary release process. The tissue samples employed, chopped tissue and synaptosomes, were prepared from rat striatum. The superfusion system employed an on-line amperometric detector to provide temporal information. In addition, liquid chromatography with electrochemical detection was used for identification and quantification of dopamine. Dopamine release could be induced from both samples by exposure to K+ in the presence of Ca2+. The presence of pargyline (0.1 mM) did not significantly affect overflow from either sample. In addition, dopamine stores could be replenished in both samples by exposure to 0.5 microM DA, an effect blocked by amphetamine, nomifensine, and amfonelic acid. However, overflow from synaptosomes showed considerably less distortion from interactions of released substances with the tissue than from chopped tissue. The temporal profile of overflow was more rapid and uptake inhibitors did not affect overflow during depolarization. Since overflow from synaptosomes appears to be more closely related to release, the temporal response of this preparation to K+ stimulations was examined in more detail. A linear relation between dopamine overflow and log (K+) was obtained with 3-s exposures to K+. In contrast, a sigmoidal relationship was obtained with 30-s exposures. Thus, the data support the concept that depolarization of nerve terminals by K+ is a biphasic process that can be temporally resolved.
已使用快速灌注装置测量多巴胺溢出，以试图获得一种系统，其中溢出是初级释放过程的一种度量。所使用的组织样本，切碎的组织和突触体，是从大鼠纹状体制备的。灌注系统采用在线安培检测器来提供时间信息。此外，液相色谱-电化学检测用于多巴胺的鉴定和定量。在Ca2+存在下，通过暴露于K+可从两个样本中诱导多巴胺释放。帕吉林（0.1 mM）的存在对两个样本的溢出均无显著影响。此外，通过暴露于0.5 microM多巴胺，两个样本中的多巴胺储备均可得到补充，此效应被苯丙胺、诺米芬辛和氨苯蝶啶阻断。然而，与切碎的组织相比，突触体的溢出受释放物质与组织相互作用的影响明显较小。溢出的时间曲线更快，并且摄取抑制剂在去极化期间不影响溢出。由于突触体的溢出似乎与释放更密切相关，因此更详细地研究了该制剂对K+刺激的时间反应。在3秒暴露于K+的情况下，多巴胺溢出与log（K+）之间获得线性关系。相比之下，在30秒暴露的情况下获得了S形关系。因此，数据支持这样的概念，即K+使神经末梢去极化是一个可以在时间上分辨的双相过程。
