gms | German Medical Science

Introduction: Stress may influence a variety of organs via the endocrine, nervous and immune systems. Here, we examined the effect of subacute stress on the auditory system of Wistar rats.

Methods: The animals were exposed for 24 h to a low-intensity and low-frequency sound (1 s, 300 Hz, 15-s-interval, 61–65 dB SPL A) and vibration in cages (Joachim et al. 2003). At different times after finishing stress, we measured the auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In addition, we analyzed the concentrations of corticosterone and selected cytokines in serum. Moreover, the transcriptional expressions of prestin, glucocorticoid receptor, hypoxia-inducible factor-1alpha, nitric oxide synthase, inducible (iNos) and heat shock factor-1 (Hsf1) were measured in the organ of Corti (OC) or spiral ganglion (SG) (real-time RT-PCR, 2–ΔΔCt, reference gene ribosomal subunit 16).

Results: Following stress, the ABR and DPOAE thresholds were significantly reduced as compared to controls. This auditory hypersensitivity was most pronounced at 3–6 hours after stress exposure and still present 24 hours later. One week after stress, the thresholds of stressed animals returned to control levels. We observed an increase of the concentrations of corticosterone and tumor necrosis factor-alpha in serum 3–6 hours after stress and an increase of the transcriptional expression of prestin in the OC. In the SG, expressions of iNos and Hsf1 increased 24 hours after stress.

Conclusion: Subacute stress, which induces modulation in endocrine, nervous and immune systems, results in temporary hypersensitivity of the auditory system.