Neuronal communication mediated by gap junctions that form electrical synapses composed of connexin36 in the hippocampus
Loading...
Date
2020-12
Authors
Thomas, Deepthi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Granule cells in the hippocampus project axons to hippocampal CA3 pyramidal cells where they form large mossy fiber terminals. We have reported the presence of gap junction protein connexin36 (Cx36) specifically in the stratum lucidum of rat ventral hippocampus, thus creating morphologically mixed synapses that have the potential for dual chemical/electrical transmission capabilities. There is some electrophysiological evidence that these terminals have a gap junction-mediated electrical transmission component under some conditions. Here, we used various approaches to further characterize molecular and electrophysiological relationships between the Cx36-containing gap junctions at mossy fiber terminals and their postsynaptic elements. In the CA3b and CA3c hippocampal regions, the vast majority of these terminals, identified by their selective expression of vesicular zinc transporter-3 (ZnT3), displayed multiple, fine immunofluorescent Cx36-puncta representing gap junctions, which were absent at mossy fiber terminals in the dorsal hippocampus. These puncta were invariably found in close proximity to the protein constituents of adherens junctions (i.e., N-cadherin and nectin-1) that are a structural hallmark of mossy fiber terminals that contact dendritic shafts of CA3 pyramidal cells, thus indicating the loci of gap junctions at these contacts. Cx36-puncta were also associated with adherens junctions at mixed synapses in other regions of the CNS. Electrophysiologically induced long-term potentiation of field responses evoked by mossy fiber stimulation was greater in the ventral than dorsal hippocampus, and it remains to be determined whether the electrical component of transmission at mossy fiber terminals contributes to the enhancement of these responses.
Description
Keywords
Mixed electrical synapses, Hippocampus, Electrical coupling