DEVELOPMENT OF ENDOCOCHLEAR POTENTIAL AND ITS NEGATIVE COMPONENT IN MOUSE COCHLEA

The chronological developmental processes of endocochlear potential (E P) and negative endocochlear potential (-EP) were investigated as a fu nction of age from birth in the basal and second cochlear turns in nor mal ICR-strain mice. The EP of the basal turn developed between 5 and 17 days after birth (DAB). The -EP of the basal turn attained to its m ature level on 11 DAB and it increased its absolute value further betw een 12 and 16 DAB and then, recovered to its mature level again on 20 DAB. The developmental processes of EP and -EP of the second turn foll owed similar courses to these of the basal turn although they were sev eral millivolts different on each day in detail. The results suggest t hat the developmental processes of the + EP and the -EP are different. The time of reaching minimum -EP during anoxia were measured and the rate of EP decline were calculated on each animal. The rate of EP decl ine increased rapidly on 10 DAB, almost coinciding the day which EP be gan to increase abruptly. Although the rate of EP decline is influence d by several processes, this result showed one of the possibility that the sensitivity of the stria vascularis to hypoxia may develop parall el to the development of the EP.