Membrane Resistance in Endolymphatic Walls of the First Turn of the Guinea-Pig Cochlea

Microelectrodes were inserted into the three scalae of the first turn, and resistance measurements were fitted to a model having six pathways. The six pathways with average resistance values are (1) blood vessels inside the cochlea to the outside of the bulla—1.6 kΩ, (2) blood vessels inside the cochlea to scala tympani—0.6 kΩ, (3) blood vessels inside the cochlea to scala vestibuli—0.8 kΩ, (4) blood vessels inside the cochlea via the stria vascularis to scala media—13 kΩ, (5) scala media direct to scala tympani (organ of Corti)—24 kΩ, (6) scala media direct to scala vestibuli (Reissner's membrane) 46 kΩ. There was no indication of a need to include a direct pathway from scala tympani to scala vestibuli. The “length constant” of scala media in the first turn is about 2.0 mm. The resistance changes due to moderate sound were found to be small, but measurable. Changes of resistance with anoxia showed first a decrease and then an increase in the resistance from scala media to ground.