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An electron microscopic, immunogold analysis of glutamate and glutamine in terminals of rat spinocerebellar fibers
Author(s) -
Ji Zhongqi,
Aas JanErik,
Laake Jon,
Walberg Fred,
Ottersen Ole Petter
Publication year - 1991
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903070210
Subject(s) - glutamate receptor , biology , synaptic vesicle , immunocytochemistry , vesicle , immunogold labelling , golgi apparatus , biophysics , mossy fiber (hippocampus) , glutamatergic , microbiology and biotechnology , biochemistry , neuroscience , ultrastructure , anatomy , cell , central nervous system , endocrinology , dentate gyrus , receptor , membrane
A semiquantitative, electron microscopic immunocytochemical procedure based on the use of colloidal gold particles as markers was employed to analyze the subcellular distribution of glutamate and glutamine, a major glutamate precursor, in a subpopulation of spinocerebellar mossy fiber terminals. These terminals were identified by anterograde transport of a horseradish peroxidase‐wheat germ agglutinin conjugate, injected in the thoracic spinal cord. Gold particles signalling glutamate‐like immunoreactivity were enriched over clusters of synaptic vesicles relative to organelle‐free cytoplasmic matrix, and there was a strong positive correlation between gold particle and synaptic vesicle densities (correlation coefficient 0.94). Gold particles indicating glutamine‐ike immunoreactivity showed a much weaker correlation with vesicle density (correlation coefficient 0.36) and were about equally concentrated over cytoplasmic matrix as over clusters of synaptic vesicles. Compared with the mossy fibers, the putative GABAergic Golgi cell terminals exhibited a lower level of glutamate‐like immunoreactivity, which was very weakly correlated with the vesicle density (correlation coefficient 0.27). The level of glutamine‐like immunoreactivity in the Golgi cell terminals was similar to that in mossy fibers, but much lower than that in glial cells. The anterogradely labelled mossy fiber terminals were not enriched in immunoreactivities for aspartate or GABA. These results suggest that the level and subcellular distribution of glutamate in presumed glutamatergic terminals differs from that in terminals in which glutamate only serves metabolic or precursor roles, and that these differences can be exploited in immunocytochemical studies aimed at identifying glutamate‐using neurons. In contrast, glutamine immunocytochemistry does not seem to be generally useful in this regard.