Pressure difference between perilymph and endolymph

Endolymphatic and perilymphatic pressures were measured simultaneously with two sets of a servo-nulling system in guinea pigs. This method seems to reveal pressure relationships between the perilymph and the endolymph in excellent detail, because the servo-nulling system is the most suitable equipment for studying the pressure of inner ear fluid and both pressures can be measured simultaneously with the same precision. The results were different from those of our previous study in which endolymphatic and perilymphatic pressures were measured by different systems.(1) Under physiological conditions there was no significant pressure difference between perilymph and endolymph.(2) Anoxia or oral administration of glycerol caused no pressure difference between the endolymph and the perilymph.(3) When the perilymphatic space was opened to the atmosphere, no significant pressure change was seen in either the endolymph or the perilymph.The boundaries between the perilymph and the endolymph, especially Reissner's membrane, may be too weak to sustain pressure differences between them.