Efthimiopoulos S, Giompres P, Valcana T
Department of Biology, University of Patras, Greece.
J Neurosci Res. 1991 Aug;29(4):510-9. doi: 10.1002/jnr.490290411.
Recent evidence indicates that the cerebellum has a dopaminergic system. In order to elucidate further the dopaminergic system in the cerebellum, we investigated the transport of dopamine (DA) in synaptosomal preparations of normal and reeler mice. For comparative purposes we also studied DA transport in synaptosomal preparations from striatum and frontal cortex and compared DA transport to noradrenaline (NA) transport. [3H]-DA transport into cerebellar synaptosomes was found to be a Na(+)-dependent, two component system--a high affinity, low capacity and a low affinity, high capacity. In striatum [3H]-DA is transported by a similar high but different low affinity component. Maximal velocities of both transport components in the striatum were higher than the corresponding ones in the cerebellum. In the frontal cortex we also observed two [3H]-DA transport components with affinities significantly lower than those in cerebellum and striatum. [3H]-NA transport into synaptosomes, prepared from the three brain regions studied, showed two transport components with similar Kt and Vmax values, except for the high affinity component in striatum whose affinity is lower. In reeler mice [3H]-DA transport was different from normal only in the cerebellum where the maximal velocity for both transport components was significantly higher (2x). In contrast, no significant difference was observed in the transport of [3H]-NA. The accumulated [3H]-DA from cerebellar slices was found to be releasable by K+ stimulation, in a Ca(++)-dependent manner, and most of the released radioactivity was in the form of [3H]-DA. These results indicate that in the cerebellum there is a low-density dopaminergic system which is distinct from the corresponding noradrenergic system.
最近的证据表明，小脑存在一个多巴胺能系统。为了进一步阐明小脑中的多巴胺能系统，我们研究了正常小鼠和reeler小鼠突触体标本中多巴胺（DA）的转运。为了进行比较，我们还研究了纹状体和额叶皮质突触体标本中的DA转运，并将DA转运与去甲肾上腺素（NA）转运进行了比较。发现[3H]-DA转运到小脑突触体中是一个依赖Na(+)的双组分系统——一个高亲和力、低容量组分和一个低亲和力、高容量组分。在纹状体中，[3H]-DA由一个类似的高亲和力但不同的低亲和力组分转运。纹状体中两个转运组分的最大速度均高于小脑中相应的组分。在额叶皮质中，我们也观察到两个[3H]-DA转运组分，其亲和力明显低于小脑和纹状体中的组分。[3H]-NA转运到所研究的三个脑区制备的突触体中，显示出两个转运组分，其Kt和Vmax值相似，除了纹状体中的高亲和力组分，其亲和力较低。在reeler小鼠中，[3H]-DA转运仅在小脑中与正常情况不同，其中两个转运组分的最大速度显著更高（2倍）。相比之下，[3H]-NA的转运未观察到显著差异。发现从小脑切片中积累的[3H]-DA可通过K+刺激以Ca(++)依赖的方式释放，并且大部分释放的放射性是以[3H]-DA的形式存在。这些结果表明，小脑中存在一个低密度的多巴胺能系统，它与相应的去甲肾上腺素能系统不同。
