HOMOTYPIC AND HETEROTYPIC COUPLING MEDIATED BY GAP-JUNCTIONS DURING GLIAL-CELL DIFFERENTIATION IN-VITRO

Intercellular communication mediated by gap junctions was investigated during oligodendrocyte differentiation in primary and secondary cell cultures from newborn and adult rats. Two types of communication were considered: ionic coupling and dye-coupling between similar oligodendr ocytes selected at the same stage of differentiation (homotypic) and d ye-coupling between oligodendrocytes and astrocytes (heterotypic). Int ercellular diffusion of fluorescent probes and double whole-cell recor dings were used to test the incidence of dye and ionic communication r espectively. Progenitor cells, identified with A2B5 antibodies, were c haracterized by the absence of ionic and dye-coupling, whereas oligode ndrocytes, identified with galactosylceramide antibodies, exhibited bo th types of communication. This homotypic coupling was inhibited by va rious uncoupling agents, but unaffected by treatments which increased the intracellular concentration of cAMP. In cocultures of astrocytes a nd oligodendrocytes, Lucifer yellow and sulphorhodamine B were exchang ed in both directions. This heterotypic dye-coupling, which could be b locked by octanol, first appeared after 3 weeks in culture and increas ed to an incidence of 25% after 6 weeks, a developmental pattern compa rable to homotypic dye-coupling between oligodendrocytes. In contrast, during the same period, progenitors and microglia were never observed to be dye-coupled with astrocytes.