Marking tip positions of fine capillary microelectrodes in teleost nervous tissue

A method is decribed for marking the tip position of fine (1-4 microns) capillary electrodes following recording. Evans blue dissolved in teleost Ringer, which at the same time serves as recording electrolyte, is deposited by iontophoresis. In frozen sections the spots appear as blue labelled neurones with a light microscope, or as a brilliant red neurones surrounded by reddish tissue with a fluorescence microscope. Counterstaining with cresyl fast violet (nissl stain) is possible.