Morphology and Electrical Properties of Schwann Cells around the Giant Axon of the Squids Loligo forbesi and Loligo vulgaris

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 243; no. 1308; pp. 255 - 262
• Main Authors: Brown, E. R., Bone, Quentin, Ryan, K. P., Abbott, N. J.
• Format: Journal Article
• Language: English
• Published: London The Royal Society 22.03.1991
• Subjects: Animals; Axons; Axons - physiology; Axons - ultrastructure; B lymphocytes; Basement membrane; Cell Communication; Cell membranes; Decapodiformes; Electrodes; Electrophysiology; Homeostasis; Loligo forbesi; Loligo vulgaris; Marine; Membrane potential; Membrane Potentials; Neuroglia; Neurons; Potassium - metabolism; Schwann cells; Schwann Cells - cytology; Schwann Cells - physiology; Squid
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.1991.0039

The first successful dye-fills of Schwann cells around the split giant axon of Loligo show them to be spindle-shaped cells ca. 600 µm long and 20 µm wide lying parallel to the axonal axis. There are some 50000 Schwann cells per cm2 of axonal membrane. Only a small part (ca. 6 % of each Schwann cell membrane) is in contact with the periaxonal space, the remainder is overlain by adjacent Schwann cells, or applied to the basal lamina. The mean membrane potential of the Schwann cells in artificial seawater (ASW) varies from around -40 mV in fresh split-axon preparations to around -60 to -70 mV after 1-2 h; this hyperpolarization is not seen in preparations dissected and maintained in Ca2+ -free ASW. Electrical- and dye-coupling (abolished by prior octanol treatment) is present between Schwann cells, but is weaker in cells with lower (less negative) membrane potentials. The implications for potassium homeostasis around the axon are briefly discussed.