Subcellular fractionation on Percoll gradient of mossy fiber synaptosomes: evoked release of glutamate, GABA, aspartate and glutamate decarboxylase activity in control and degranulated rat hippocampus.
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.
Taupin
P
P
INSERM U 29, Paris, France.
Ben-Ari
Y
Y
Roisin
M P
MP
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002851:Chromatography, High Pressure Liquid; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D005968:Glutamate Decarboxylase / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D006624:Hippocampus / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000201:enzymology / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000378:metabolism* / Q000528:radiation effects; D013574:Synaptosomes / Q000201:enzymology / Q000378:metabolism* / Q000528:radiation effects; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D000596:Amino Acids; D005971:Glutamates; D001224:Aspartic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase