AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 3 493-R498, Copyright © 1986 by American Physiological Society
Development of mammalian endocochlear potential: normal ontogeny and effects of anoxia
N. K. Woolf, A. F. Ryan and J. P. Harris
The development of the positive endocochlear potential (EP), the negative
anoxic EP, and the organ of Corti potential were measured at various
postnatal ages in the Mongolian gerbil, beginning at 8 days after birth
(DAB). The organ of Corti potential (OCP) was present at 8 DAB but averaged
21% less than the adult value. OCP increased regularly with age, reaching
adult values of -90 mV by 14 DAB. The positive EP was first observed at 10
DAB, at which age it averaged only 2-3 mV. This potential increased
monotonically between 10 and 20 DAB, by which time it had reached the adult
value of 75 mV. Anoxia did not result in a negative EP until 12 DAB, at
which age this potential averaged -7 mV. The negative anoxic EP matured
more rapidly than the positive EP, achieving the adult value of 40 mV by 18
DAB. During development the positive EP appeared to closely parallel the
maturation of glucose metabolism in the stria vascularis. The negative
anoxic EP was more closely related temporally to the development of
cochlear microphonic potential (CM) thresholds. It is hypothesized that
changes which occur between 10 and 16 DAB in the apical membranes of the
cochlear hair cells contribute to the maturation of both CM and the
negative anoxic EP.
