Morales E, Tapia R
Departamento de Neurociencias, Universidad Nacional Autónoma de México, D.F.
Brain Res. 1987 Sep 8;420(1):11-21. doi: 10.1016/0006-8993(87)90234-4.
We have studied some properties of the uptake and release of labeled gamma-aminobutyric acid (GABA), glycine, serotonin and choline in a purified fraction of glomeruli and in slices of the granular layer of the rat cerebellum. The uptake of both GABA and glycine into the glomerulus particles was dependent on the presence of Na+ in the medium. In contrast, the uptake of both serotonin and choline was Na+-independent. In slices of the granular layer also a slight Na+-dependence was observed for both serotonin and choline uptake; imipramine and hemicholinium partially inhibited the uptake of serotonin and choline, respectively. Choline uptake into the glomerulus particles showed two components, with apparent Km values of 16.8 and 102 microM. GABA release was stimulated by K+-depolarization about 100% (peak stimulation) and this value was reduced to 50% when Ca2+ was omitted. The release of glycine was stimulated more rapidly and notably than GABA (200%) and this stimulation was completely abolished in the absence of Ca2+. Serotonin release from the glomerulus particles was only slightly stimulated by depolarization, but this stimulation was strictly Ca2+-dependent. In slices of the granular layer, this stimulation was considerably larger (about 40%) and it was also almost totally dependent on Ca2+. In contrast, after loading with labeled choline the release of radioactivity from both the glomerulus particles and the cerebellar slices was not stimulated at all by K+-depolarization, either in the presence or in the absence of Ca2+. Most of the radioactivity released spontaneously corresponded to choline, and only a small proportion (8-14%) to acetylcholine. From the results of the release experiments and taking into account the pertinent data from the literature, it is concluded that GABA and glycine are probably the transmitters of different populations of Golgi axon terminals, whereas serotonin might be the transmitter of at least a certain population of the mossy fiber giant terminals, in the rat cerebellar glomeruli. In contrast, acetylcholine does not seem to have any transmitter role in the synaptic structures of the glomeruli.
我们研究了标记的γ-氨基丁酸（GABA）、甘氨酸、5-羟色胺和胆碱在大鼠小脑纯化的肾小球部分以及颗粒层切片中的摄取和释放特性。GABA和甘氨酸进入肾小球颗粒的摄取依赖于培养基中Na⁺的存在。相反，5-羟色胺和胆碱的摄取不依赖于Na⁺。在颗粒层切片中，5-羟色胺和胆碱的摄取也表现出轻微的Na⁺依赖性；丙咪嗪和半胱氨酸分别部分抑制5-羟色胺和胆碱的摄取。胆碱进入肾小球颗粒的摄取表现出两个组分，表观Km值分别为16.8和102μM。K⁺去极化刺激GABA释放约100%（峰值刺激），当省略Ca²⁺时，该值降至50%。甘氨酸的释放比GABA更快且更显著地受到刺激（200%），并且在没有Ca²⁺的情况下这种刺激完全消失。肾小球颗粒中5-羟色胺的释放仅受到去极化的轻微刺激，但这种刺激严格依赖于Ca²⁺。在颗粒层切片中，这种刺激要大得多（约40%），并且几乎完全依赖于Ca²⁺。相反，在用标记胆碱加载后，无论是在有Ca²⁺还是无Ca²⁺的情况下，K⁺去极化都根本不刺激来自肾小球颗粒和小脑切片的放射性释放。自发释放的大部分放射性对应于胆碱，只有一小部分（8-14%）对应于乙酰胆碱。从释放实验的结果并考虑到文献中的相关数据，可以得出结论，在大鼠小脑肾小球中，GABA和甘氨酸可能是不同群体高尔基轴突终末的递质，而5-羟色胺可能是至少某些群体苔藓纤维巨终末的递质。相反，乙酰胆碱似乎在肾小球的突触结构中没有任何递质作用。
