Glio-axonic junctional like complexes at the Mauthner cell's axon cap of teleosts: a possible morphological basis for field effect inhibitions.

Differentiated contacts were identified by electron microscopy between glia and axons as they enter the axon cap which surrounds the initial segment of the teleost's Mauthner cell. At these regions, the cleft of adjacent membranes is 20-25 nm wide and contains clods of electron-dense material with a pseudo-periodicity of 10-30 nm. These junctions, referred to as 'septate-like junctions', presumably contribute to the compartmentalization of the axon cap and, therefore, to its elevated resistivity which underlies the generation of field effect inhibitions.