Ac. Suryadevara et al., Auditory nerve fibers in young and quiet-aged gerbils: morphometric correlations with endocochlear potential, HEARING RES, 161(1-2), 2001, pp. 45-53
The number, size and distribution of myelinated nerve Fibers were analyzed
in the osseous spiral lamina (OSL) of young and old gerbils raised in a qui
et environment. Because decreased endocochlear potentials (EPs) play a sign
ificant role in age-related hearing loss in the gerbil, we correlated morph
ometric and topographical data for nerve Fibers with EP measurements in the
same ear. Fibers were analyzed at the 2 and 10 kHz locations. The number o
f fibers at the 2 kHz location ranged from 12 to 47% greater than at the 10
kHz place in both young and aged specimens. No significant correlation was
found between the number of fibers and the EP. Nerve fibers in gerbil tend
to be distributed vertically by size within the OSL [Slepecky et al. (2000
) Hear. Res. 144, 124-134], a result also found in cats and guinea pigs. Sm
aller fibers are more often found towards the scala vestibuli side of the O
SL, whereas larger fibers are concentrated towards the scala tympani. The p
resent data confirmed this distribution in young gerbils; however. in aged
cars the distribution often became more uniform. Moreover. fiber distributi
on and ganglion cell size were highly correlated with EP. As EP declined. t
he fiber size distribution in the OSL became more uniform and the mean cros
s-sectional area of spiral ganglion cells and fiber diameter decreased. Thu
s, for whatever reason, certain indices of auditory nerve fiber morphometri
cs appear to be associated with the EP. (C) 2001 Elsevier Science B.V. All
rights reserved.