Evidence for increased nitric oxide production in the auditory brain stem of the aged dwarf hamster (Phodopus sungorus): an NADPH-diaphorase histochemical study
S. Reuss et al., Evidence for increased nitric oxide production in the auditory brain stem of the aged dwarf hamster (Phodopus sungorus): an NADPH-diaphorase histochemical study, MECH AGE D, 112(2), 2000, pp. 125-134
Age-related changes of the auditory system such as presbyacusis are believe
d to be due, at least in part, to alterations of central structures. The su
perior olivary complex (SOC), a group of interrelated brain stem nuclei, pr
ojects to a variety of neuronal structures including the cochlea and the in
ferior colliculus (IC). The soluble gas nitric oxide (NO), believed to func
tion as a neuroactive substance within the SOC and cochlea, is thought to b
e involved in ageing processes. Since it is unknown whether NO-production i
s altered in the ageing auditory system, the present study was conducted to
investigate whether the number of NO-producing cells in the SOC is changed
with increasing age. The histochemical detection of NADPH-diaphorase activ
ity (NADPH-d), a marker for neurons containing NOS, was utilized to investi
gate the numbers of NO-producing cells in the SOC of adult and senile Djung
arian dwarf hamsters (Phodopus sungorus). Our results demonstrate that the
number of stained neurons was almost doubled in the SOC of senile hamsters.
The most distinct changes were observed in the medial nucleus of the trape
zoid body. In contrast, NO-producing preganglionic sympathetic neurons of t
he spinal intermediolateral nucleus, which was studied for comparison, did
not exhibit significant differences between adult and senile animals. It is
concluded that the increase of NO-production in the ageing auditory brain
stem, as revealed by our data, may be related to hearing impairments with i
ncreasing age. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.