Coupling between giant axon Schwann cells in the squid

The nature of dye and electrical coupling between Schwann cells from the the squid giant axon, determined with microelectrodes, is described. Dye coupling (sensitive to dissection in sea water containing Ca2+) and electrical coupling exists between Schwann cells. The electrical length constant of the Schwann-cell sheath is 25 mu m and 100 mu m along the axon circumference and long axis respectively. Schwann-cell membrane resistance is similar to 500 Omega cm(2) (corrected for coupling between cells). The coupling ratio between cells is 1:0.3, and is reduced by 2 mM octanol (1:0.03) and increased by 2 mM Ba2+ (1:0.45). We conclude that as Schwann cells are weakly coupled and have a relatively low membrane resistance they are unlikely to be involved in the spatial buffering of axonally released K+.