Gap junction-mediated bidirectional signaling between human fetal hippocampal neurons and astrocytes

Gap junctions are clusters of intercellular channels that connect the interiors of coupled cells. In the brain, gap junctions function as electrotonic synapses between neurons and as pathways for the exchange of metabolites and second-messenger molecules between glial cells. Astrocytes, the most abundant glial cell type coupled by gap junctions, are intimately involved in the active control of neuronal activity including synaptic transmission and plasticity. Previous studies have suggested that astrocytic-neuronal signaling may involve gap junction-mediated intercellular connections; this issue remains unresolved. In this study, we demonstrate that second-trimester human fetal hippocampal neurons and astrocytes in culture are coupled by gap junctions bidirectionally; we show that human fetal neurons and astrocytes express both the same and different connexin subtypes. The formation of functional homotypic and heterotypic gap junction channels between neurons and astrocytes may add versatility to the signaling between these cell types during human hippocampal ontogeny; disruption of such signaling may contribute to CNS dysfunction during pregnancy.