Ribonucleic acid changes in the brain, spiral ganglion, and adrenal cortex of noise-exposed rats

Abstract

Microspectrophotometric determinations of neuronal RNA levels were made in selected brain areas (auditory cortex, optic cortex, and hippocampus), in adrenal cortical cells, and in cochlear receptor elements from adult male albino rats exposed to a 60-min noise (100–120 dB re 0.0002 μbar, 350–20 000 Hz). Control animals were maintained at ambient sound pressure levels (ca. 40 dB). Animals were sacrificed at 1-, 4-, 8-, and 24-hour postexposure intervals. RNA was quantified in azure-B-stained tissue sections which were pretreated with DNase. A transient RNA elevation was evidenced in neurons from the three brain regions analyzed during the 1- to 8-hour postexposure interval. Adrenal cortical cells also exhibited increased RNA levels at corresponding postexposure time intervals, whereas no appreciable stimulation of RNA synthesis was evidenced in spiral ganglion neurons of the cochlea during a 24-hour period following cessation of auditory stimulation. The latency of RNA activation in brain elements, coupled with the similarity in the pattern of adrenal stimulation suggests that nucleic acid responses of brain neurons may be hormonally mediated and not a direct manifestation of excitation via auditory neural pathways. [Research aided by the Office of Environmental Quality Programs and the Center for Air Environment Studies.]