Effects of Hyperosmotic Solutions on Fluid Pressure and DC Potential in the Guinea Pig Cochlea

Abstract

Effects of glycerol, urea and mannitol on hydrostatic pressure of labyrinthine fluids and DC potential were studied in the guinea pig cochlea with a servo-controlled micropipet system. Each osmotic agent produced substantial pressure reduction in both endo- and perilymph with a maximum reduction during 20-30 min after the administration. Difference in pattern of the pressure changes between the inner ear fluids and CSF indicates a possible dehydration effect in the labyrinth for glyceral and urea, but an ambiguous effect for mannitol. These three agents diminished the endocochlear DC potential with a maximum diminution at five minutes. Difference in time course between the pressure and the DC potential reduction suggests the DC potential may not be diminished by the osmotic dehydration effect. Metabolic effect of these osmotic agents on the stria vascularis is considered to be a possible cause of the DC potential change.