Intracellular injection of antibodies to the 27-kDa liver gap junction polypeptide have been shown previously to uncouple pairs of cultured mammalian hepatocytes, cardiac myocytes, and ganglionic neurons (Proc. Natl. Acad. Sci. U.S.A., 82 (1985) 2412-2416). In confluent primary cultures of astrocytes, similar injections significantly reduced dye coupling for cells closer than 80 micron to the injected glial cell. Western blots identified a 27-kDa protein in extracts of the astrocyte cultures that cross-react with the gap junction-specific antibodies. These results suggest that homologous gap junction polypeptides exist in liver and glial cells.