Precise extracellular marking in the auditory nerve with high impedance micropipettes

A procedure is described which permitted for the first time accurate marking of the recording sites of primary auditory nerve fibers, peripheral to their entrance into the brainstem. The technique, which involves a modification of the fast green FCF dye marking procedure, does not interfere with the recording quality of the high-impedance micropipettes, requires no special histology, permits routine production od 5-15 micron diameter marks at extracellular recording sites, and employs a dye known to be noncytotoxic.