Development of endocochlear potential and compound action potential in the rat.
The present study was designed to investigate the developmental changes of the endocochlear potential and compound action potential simultaneously from rat pups of various ages. Animals were anesthetized with ketamine/xylazine, and the endocochlear potential was measured with a glass microelectrode. At the same time, a wire electrode was placed on the round window to record the click-evoked compound action potential. The endocochlear potential was found to be very low during the first few days of postnatal life. A rapid increase in the value of the endocochlear potential was noted between eleven and thirteen days of age, and adult-like values were recorded by seventeen days of age. Compound action potential responses were recorded at thirteen days of age to high intensity clicks, followed by a progressive improvement of thresholds and reduction of latencies. The development of the endocochlear potential and compound action potential was found to be reciprocally related - as the magnitude of the endocochlear potential increased, the compound action potential threshold declined with increasing age. The development of the endocochlear potential was found to closely approximate the development of enzymatic activity of sodium, potassium-ATPase in the stria vascularis reported by Kuijpers (1974).
Rybak
L P
LP
Department of Surgery, Southern Illinois University School of Medicine, Springfield 62794-9230.
Whitworth
C
C
Scott
V
V
D000200:Action Potentials / Q000502:physiology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000375:Aging; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000502:physiology*; D003055:Cochlear Microphonic Potentials; D005072:Evoked Potentials, Auditory; D008839:Microelectrodes; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013316:Stria Vascularis / Q000201:enzymology
D000262:Adenylyl Cyclases; D000254:Sodium-Potassium-Exchanging ATPase