Pressure relationship between perilymph and endolymph in guinea pigs.

The pressure difference between the perilymph and the endolymph was studied in guinea pigs, using two sets of a servo-nulling system. Asphyxia caused characteristic pressure changes both in the perilymph and in the endolymph, but no pressure difference was seen between them. When the perilymphatic space was opened to the atmosphere, asphyxia did not cause such dynamic pressure changes either on the perilymph or the endolymph. An increase in the perilymphatic pressure induced by the infusion of artificial cerebrospinal fluid into the subarachnoid space resulted in an increase in the endolymphatic pressure, but no pressure difference between the endolymph and the perilymph was evident, regardless of the patency of the vestibular aqueduct. The authors conclude that the endolymphatic pressure is dependent on the perilymphatic pressure and there is no pressure difference between them.