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Synaptic vesicle protein synaptoporin is differently expressed by subpopulations of mouse hippocampal neurons
Author(s) -
Singec Ilyas,
Knoth Rolf,
Ditter Margarethe,
Hagemeyer Christoph E.,
Rosenbrock Holger,
Frotscher Michael,
Volk Benedikt
Publication year - 2002
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.10371
Subject(s) - fascia dentata , parvalbumin , biology , hippocampal formation , calretinin , synaptic vesicle , in situ hybridization , interneuron , neuroscience , calbindin , hippocampus , colocalization , immunoelectron microscopy , pyramidal cell , glutamate decarboxylase , granule cell , microbiology and biotechnology , dentate gyrus , vesicle , messenger rna , immunohistochemistry , inhibitory postsynaptic potential , biochemistry , immunology , membrane , gene , enzyme
In the hippocampus, the synaptic vesicle protein synaptoporin (SPO) has been reported to be exclusively enriched in the granule cell axons, the mossy fibers. In this study, we show that in adult rats and mice SPO immunoreactivity (IR) is also detectable in strata oriens, radiatum, and lacunosum‐moleculare of CA1–CA3, as well as perisomatically in the hippocampus proper and fascia dentata. In situ hybridization confirmed that SPO mRNA was present in granule cells and CA3 pyramidal cells but not in CA1 pyramidal cells. Importantly, cells scattered throughout the hippocampal layers resembling the distribution of interneurons were found to synthesize high amounts of SPO mRNA, too. Thus, these findings indicate that SPO expression in the hippocampus was underestimated until now. Moreover, double‐labeling immunohistochemistry and confocal microscopy revealed selective colocalization of SPO and glutamate decarboxylase (GAD 65), a marker for γ‐aminobutyric acid (GABA)ergic terminals. To identify SPO expressing interneurons, in situ hybridization was combined with immunocytochemistry against parvalbumin (PV), calbindin (CB), calretinin (CR), cholecystokinin (CCK), and vasoactive intestinal polypeptide (VIP). We found that SPO transcripts were differentially expressed by various interneuron subpopulations in the hippocampus of C57Bl/6 mice (PV 44.2%, CB 46.3%, CR 19.3%, CCK 38.6%, VIP 59.9%). Immunoelectron microscopy for SPO labeled synaptic vesicle profiles in distinct symmetric and asymmetric synapses. In conclusion, our data demonstrate that hippocampal principal cells and interneurons display a variety of synaptic vesicles that are likely to contribute to the functional characteristics of their output synapses. J. Comp. Neurol. 452:139–153, 2002. © 2002 Wiley‐Liss, Inc.