Taupin P, Ben-Ari Y, Roisin M P
INSERM U 29, Paris, France.
Brain Res. 1994 May 2;644(2):313-21. doi: 10.1016/0006-8993(94)91695-0.
Using discontinuous density gradient centrifugation in isotonic Percoll sucrose, we have characterized two subcellular fractions (PII and PIII) enriched in mossy fiber synaptosomes and two others (SII and SIII) enriched in small synaptosomes. These synaptosomal fractions were compared with those obtained from adult hippocampus irradiated at neonatal stage to destroy granule cells and their mossy fibers. Synaptosomes were viable as judged by their ability to release aspartate, glutamate and GABA upon K+ depolarization. After irradiation, compared to the control values, the release of glutamate and GABA was decreased by 57 and 74% in the PIII fraction, but not in the other fractions and the content of glutamate, aspartate and GABA was also decreased in PIII fraction by 62, 44 and 52% respectively. These results suggest that mossy fiber (MF) synaptosomes contain and release glutamate and GABA. Measurement of the GABA synthesizing enzyme, glutamate decarboxylase, exhibited no significant difference after irradiation, suggesting that GABA is not synthesized by this enzyme in mossy fibers.
我们使用等渗Percoll蔗糖中的不连续密度梯度离心法，鉴定出富含苔藓纤维突触体的两个亚细胞组分（PII和PIII）以及富含小突触体的另外两个组分（SII和SIII）。将这些突触体组分与新生期接受照射以破坏颗粒细胞及其苔藓纤维的成年海马体中获得的组分进行比较。根据突触体在K +去极化时释放天冬氨酸、谷氨酸和GABA的能力判断，其具有活性。照射后，与对照值相比，PIII组分中谷氨酸和GABA的释放分别减少了57%和74%，但其他组分中未减少，且PIII组分中谷氨酸、天冬氨酸和GABA的含量也分别减少了62%、44%和52%。这些结果表明，苔藓纤维（MF）突触体含有并释放谷氨酸和GABA。对GABA合成酶谷氨酸脱羧酶的测量显示，照射后无显著差异，表明苔藓纤维中GABA不是由该酶合成的。
