Abstract
Noise is an inarticulate stimulus that threatens health and well-being. It compromises audition and induces a strong stress response that activates the brain at several levels. In the present study, we expose male and female rats to environmental noise in order to investigate if acute or chronic stimulation produces differential brain activation patterns. The animals were exposed to a rat’s audiogram-fitted adaptation of a noisy environment and later sacrificed to quantify the expression of the brain activity marker c-fos. Additionally, the serum corticosterone (CORT) levels were measured to elucidate possible the stress-related effects of noise. It was found that environmental noise differentially increased the serum CORT levels in male and female rats. We identified 17 brain regions outside the classical auditory circuits with a high expression of c-fos, including the hypothalamus, prefrontal cortex, habenular complex, septum, cingulate cortex, nucleus accumbens, insular cortex, amygdala, and hippocampus. Overall, we evidenced that females exhibit less intense c-fos expression in most of the examined areas. We concluded that females might be less affected by the changes produced by environmental noise.
Highlights
Noise is one of the most important pollutants in the modern world [1]
The time of exposure significantly altered the CORT levels (main effect of time, F(4, 110) = 5.738, p = 0.0003). This effect differed between the males and females (sex × time interaction, F(4, 110) = 5.488, p = 0.0003)
Differences were significant at 2 h when exposed females outpointed exposed males (p < 0.01)
Summary
Noise is one of the most important pollutants in the modern world [1]. Undesired sounds are everywhere. While the effects of noise on auditory organs have been well attended, changes in brain circuitries outside audition remain less understood. It is known that the brain is the most adaptable organ in the body, and a major target for environmental threats. It integrates information and coordinates complex responses to ensure adaptation. The auditory system is a clear example of this It obtains information about the environment from complex sound waves reaching the ears [4]. Sounds follow the classical auditory pathway that connects inputs from the auditory nerve with serial stations in the brainstem (cochlear nucleus, inferior colliculus, geniculate body, and superior olivary complex) and the auditory cortex [5]. Stress hormones (i.e., corticosterone) may exert numerous effects in the central nervous system, since many brain areas possess receptors to these hormones
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