Teleost Mauthner cap cells: intimate contact by gap junctions.

In rainbow trout the glial cap cells ensheating the Mauthner cell axon cap form a more or less double-layered arrangement consisting of fibrous astrocytes, sometimes intermingled with an oligodendrocyte. All cells of the glial wall are linked together by many gap junctions. Especially the somata of the astrocytes are connected to each other by large symmetrical gap junctions. For this reason the glial cap cells might act as an (electro-) physiological unity. Morphologically, the high axon cap resistance above all results from the densely packed glial elements. Regarding their function the astro-astrocytic gap junctions might contribute to the formation of this barrier.