Homocellular coupling in human glioma cell lines using the scrape loading method. A, Dye coupling in absence (upper row) or presence (lower row) of the gap junctional blocker CBX. After scraping, injured cells were loaded with Lucifer Yellow (LY) and Rhodamin Dextran, and GJC was assessed by the number of neighboring cells that secondarily acquired green fluorescence. Left panel, confluent monolayer of GL15 cells in phase contrast. Right panel, centrifugal (left to right) diffusion of the dye tracer LY (green) from initially loaded injured cells (yellow, because of the merge of red and green) in the same monolayer. (×100). B, histogram representing the homocellular coupling indices (mean values ± SEM) from 4 to 6 independent cultures for each condition and cell type (astrocytes, GL15 or 8-MG). Homocellular coupling index = % labeled cells out of a total of ~400–800 analyzed cells per cell culture. Addition of CBX resulted in a dramatic decrease of the homocoupling in all cases ***, p < 0.001.