An immunochemical marker for goldfish Mauthner cells.

The Mauthner (M-) cells are pair of large reticulospinal neurons that mediate tail-flip escape responses in fish. Exploring the co-localization of scaffold and gap junction proteins at mixed (electrical and chemical) synapses, we found that the use of a particular antibody against the scaffold protein Zonula Occludens-2 (ZO-2) resulted in labeling of these cells. We show here that this staining is restricted to the Mauthner cell and evenly distributed along its dendrites and axon, also prominent in small dendritic and axonal processes. Because the observed labeling is non-specific, we suggest that the antibody might recognize a soluble protein that is primarily expressed in the Mauthner cells. While the identity of this protein is presently unknown, the use of this antibody should facilitate the identification of the Mauthner cell and its fine processes during anatomical and immunohistochemical studies, which otherwise require intracellular injection of tracer molecules during electrophysiological recordings.