The presence of meningeal cells is necessary for the normal development of the glia limitans. Astrocytes comprising the adult glia limitans have several unique features, including many more gap junctions than is typical for astrocytes in the underlying molecular layer. This study examines the possible influence of meningeal cells on the establishment and maintenance of specific characteristics of astrocytes in the glia limitans. Primary cultures of rat astrocytes and meningeal cells were used to examine whether meningeal cells could alter astrocytic gap junctional dye coupling. Astrocytes and meningeal cells were grown on separate glass slides and co-cultured by forming a sandwich with the slides. The sides of the slides containing the cells faced each other and were separated by a 1 mm thick gasket along the edge of the slides. Although the meningeal cells and astrocytes were bathed in the same medium, they were separated by a distance of 1 mm and were not in direct contact during the co-culture period. The cells were co-cultured for 24, 48 or 72 hours, and astrocytic gap junctional dye coupling was examined using the gap-FRAP technique. The mean total recovery of fluorescence for control astrocytes was 14%. Astrocytes co-cultured with meningeal cells for 24 hours did not show a significant difference in the fluorescence recovery when compared to the control values. After 48 hours of co-culture, there was a significant increase in the gap junctional dye coupling. After 72 hours, gap junctional dye coupling continued to increase (total fluorescence recovery = 53%).(ABSTRACT TRUNCATED AT 250 WORDS)