Evidence for increased NADPH-diaphorase-positive neurons in the central auditory system of the aged rat.

CONCLUSIONS

The age-related increase in the production of nitric oxide (NO) suggests that this increase was related to neuron aging. Additional studies may provide information regarding aging-related changes in the central auditory system.

OBJECTIVES

Although NO has been associated with aging, it is unclear whether specific areas of the central auditory system are involved. We therefore assayed aging-related changes in NADPH-diaphorase (NADPH-d), a selective histochemical marker for NO, in the neurons of the central auditory system and other brain regions.

MATERIALS AND METHODS

The numbers of NADPH-d-stained neurons and the area and staining density of cell bodies were examined in aged (24 months old) and younger (4 months old) Wistar rats.

RESULTS

The number of NADPH-d-positive neurons in the inferior colliculus was significantly increased in aged rats (p<0.05), whereas the area of NADPH-d-positive neurons in all areas did not differ significantly between aged and younger rats (p>0.05). The staining densities of NADPH-d-positive neurons in the inferior colliculus, the auditory cortex, and the visual cortex were significantly greater in aged compared with younger rats (p<0.05).