title: Susceptibility of the endocochlear potential to pH and osmolarity changes in the perilymph of the cochlea in the guinea pig.
abstract: The effects of artificial perilymph at various pH levels and osmolarities on the endocochlear potential (EP) were investigated in a guinea pig model. In 47 ears, the mean EP was 74.5 +/- 0.5 mV in the second turn of the cochlea before perilymphatic perfusion. The artificial perilymph with a pH ranging from 5 to 9 and tonicity less than 1.25 (osmolarity, 345 mosmol/l) did not alter the EP when testings were recorded for at least 1 h. However, after the start of a perfusion with a pH less than 4, the EP declined gradually but recovered to the pre-perfusion level rapidly when the perfusion was stopped. The artificial perilymph with a pH over 10 decreased the EP considerably but showed no recovery, even after cessation of the perfusion. Tonicity more than 1.35 (osmolarity, 372.6 mosmol/l) also decreased the EP, with this decrease paralleling further increases in the tonicity used. From these data, we have concluded that a perilymph perfusate with a pH from 5 to 9 and an osmolarity less than 350 mosmol/l can be used in animal testing without any noxious effects on the EP.
authors.affiliation: Department of Otorhinolaryngology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Wakizono
authors.forename: S
authors.initials: S
authors.lastname: Komune
authors.forename: T
authors.initials: T
authors.lastname: Uemura
mesh_terms: D000818:Animals; D003055:Cochlear Microphonic Potentials; D005072:Evoked Potentials, Auditory; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007552:Isotonic Solutions; D007761:Labyrinthine Fluids / Q000502:physiology*; D009994:Osmolar Concentration; D010477:Perfusion; D010498:Perilymph / Q000502:physiology*; D000077331:Ringer's Solution
chemical_list: D007552:Isotonic Solutions; D000077331:Ringer's Solution