Effect of acute and repeated noise exposure on the behaviour and lipid peroxidation in brain tissue of male and female mice

Authors: GABRIELLA KORSÓS, KINGA FODOR, ANNAMÁRIA KISS, ANNA BLÁZOVICS, SÁNDOR GYÖRGY FEKETE

Abstract: Despite the increasingly obvious sex differences, male animals are still predominantly used to study stress and related disorders. The aim of this study was to evaluate the effects of repeated noise stress in female and male mice. In the experiment, 12 male and 12 and female SPF/VAF 6-week-old Crl:CD1(lcr) mice were used. After 5 days of acclimatization all animals were placed in the open-field for three consecutive days where each mouse spent 10 min daily without any noise treatment in order to get used to the circumstances of the test. On day 9 to record baseline behaviour the animals were placed on an open-field for 3 min and a noise mixture was played to them at 90 dB. Video recordings of the tests were made. After testing the animals were returned to their original cages and from then the noise group received noise treatment for 10 h daily. The noise mixture used for the open-field and for habituation contained similar but not identical noises. The open-field test was repeated on day 16 and day 23. At the end of the experiment the animals were weighed and-after intraperitoneal pentobarbital anaesthesia- were bled out, and their brains were removed under icy conditions. Pathological examination and histopathological sampling (spleen, thymus, adrenal glands, gonads) were performed. Because the state of the lipid peroxidation is a sensible indicator of the brain health, after homogenization the brains were frozen, then redox parameters (induced free radical levels, H-donating ability, and induced lipid peroxidation) were determined by luminometric and spectrophotometric methods. During the design and implementation of the study, we considered the EU Directive 2010/63/EU and the Hungarian Government Decree 40/2013 (14.II.) on Animal Experiments. The studies were approved by the Animal Welfare Body of the University of Veterinary Medicine Budapest under PE/EA/1277-5/2017. In our study noise treatment did not cause significant changes in the animals' behaviour. No histopathological lesions were detectable, and the bodyweight of the animals was not affected. In the control groups males had less free radical formation in the brain than females. However, the number of free radicals in the brains of females was significantly reduced by the noise treatment, whereas in males it was practically unchanged. Our results show that noise habituation and noise exposure in the open-field alone did not induce stress that was manifested in clinical and pathological signs. However, the effects of the treatments were reflected in lipid peroxidation in the brain. Our results also indicate that noise habituation significantly improves noise tolerance in female mice, but not in males.

Keywords: Noise, stress, sex, mice, brain, lipid peroxidation

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