SCANNING-INTEGRATING MICRODENSITOMETRIC ANALYSIS OF AGE-RELATED-CHANGES IN RNA-CONTENT OF CEREBROCORTICAL NEURONS IN MICE SUBJECTED TO AUDITORY-STIMULATION

Cytophotometric analyses were made of auditory cortical RNA changes in 10-week and 40-week-old mice subjected to a 30-min interval of continuous noise stimulation (100 dB re 2 × 10-5 N/m2, 0.35 to 20 kHz). Treatment groups consisted of young and old noise-exposed mice killed at 0-, 1-, and 4-h intervals after cessation of noise stimulation. Corresponding groups of control mice were not subjected to noise stimulation. Quantification of neuronal RNA changes was made on an individual cell basis using scanning-integrating microdensitometry of azure B-stained brain sections. In the noise-stimulated groups we found that auditory cortical neurons from older mice synthesized and accumulated RNA to the same extent if not more than those of younger mice. The similarity in the pattern and extent of neuronal RNA augmentation in old and young mice after sensory stimulation suggests there is no marked age-related impairment in the capacity of cerebrocortical cells to synthesize RNA. Prior to stimulation we found that older mice had appreciably more neurons with very low RNA values compared to younger mice; older mice also exhibited a more rapid restoration of brain RNA toward control values at the 4-h postexposure interval. © 1979.