Gap-junctional coupling between neurons and astrocytes in primary central nervous system cultures

Cap-junctional communication between neurons and astrocytes dissociated fro m rat brain was identified in culture by using dye-transfer assays and elec trophysiological measurements. Cell types were identified by using antibodi es against beta-tubulin III, glial fibrillary acidic protein, and 2',3'-cyc lic-nucleotide phosphohydrolase, which are antigenic determinants of neuron s, astroglia, and oligodendrocytes, respectively, Dye coupling was examined as a function of time after dissociated embryonic brain cells were plated onto confluent monolayers of postnatal astrocytes by intracellularly inject ing the fluorochrome Lucifer yellow. Coupling of neurons to the astrocytic monolayer was most frequent between 48 h and 72 h in culture and declined o ver the next 4 days. This gradual uncoupling was accompanied by progressive neuronal maturation, as indicated by morphological measurements in camera lucida drawings. Dye spread was abolished reversibly by octanol, an agent t hat blocks gap junction channels in other systems, Double whole-cell voltag e-clamp measurements confirmed the presence of heterocellular electrical co upling in these cocultures, Coupling was also seen between neurons and astr ocytes in cocultures of cells dissociated from embryonic cerebral hemispher es but was rarely detectable in cocultures of postnatal brain cells. These data strongly suggest that junctional communication may provide metabolic a nd electrotonic interconnections between neuronal and astrocytic networks a t early stages of neural development and that such interactions are weakene d as differentiation progresses.