Hydrostatic pressure measurement of endolymph and perilymph in the guinea pig cochlea.

Hydrostatic pressures of endolymph and perilymph were measured with a servo-micropipet system. The validity of the experiment was assessed by observation of endolymphatic pressure changes during and after 3 minutes of anoxia. Simultaneous recording of endocochlear DC potential confirmed the location of the electrode tip. Following verification of the efficacy of the system, measurements of endolymphatic or perilymphatic pressures were made in ten guinea pigs in which the middle ears had been filled with a saturated sodium chloride solution. Both endolymphatic and perilymphatic measurements showed gradual declines in pressure, with minimum pressure at 15 to 20 minutes and slow recovery during the next 20 minutes.