Two noise-exposure schedules differentially affect rat behavioral parameters and can be altered by enriched environment rearing

MOLINA, SJ; CAPANI, F; GUELMAN, LR

Río de Janeiro

Congreso; 9th IBRO World Congress on Neuroscience; 2015

International Brain Research Organization (IBRO)

It is know n that noise exposure can induce transient or permanent hearing loss. How ever, few data are available regarding its effects onextra-auditory structures, mainly w ithin developing Central Nervous System.Previous studies of our laboratory show ed that exposure of immature rats (15-days-old) to moderate noise during 2 hours, in differentexposure schedules, can induce hippocampus-related behavioral, biochemical and histological alterations. Moreover, rearing these animalsin an enriched environment (EE) has show n to be an effective protective tool w hich almost fully prevented noise-induced behavioralchanges.Nevertheless, no data on the behavioral effects induced by noise exposure at earlier ages have been obtained yet.Therefore, the aim of the present w ork w as to test the behavioral effects induced in 7-days-old rats after moderate noise exposure usingdifferent schedules, and if EE can prevent them.Rats of 7 days w ere exposed during 2 hours to w hite noise (95-97 dBA), for one day (acute exposure) or five consecutive days (chronicexposure), using an ?ad-hoc? sound camera. After w eaning, groups of 3-4 rats w ere transferred to an enriched cage, consisting of toys, aw heel, tunnels and ramps, w hile other groups w ere placed in standard cages. One w eek later, different behavioral tests w ere performed.Results show that rats exposed to chronic noise had a better performance in associative memory task w hen compared w ith controlanimals, w hereas no significant changes w ere found in rats exposed to acute noise. Interestingly, all the exposed rats that w ere reared inan EE show ed a better performance on this task.On the other hand, no changes in habituation memory w ere observed in rats exposed to noise in either noise schedule. How ever, significantdifferences w ere found in exposed rats reared in an EE. Finally, chronic noise-exposed rats show ed no changes in anxiety-like behaviors,w hereas rearing in an EE induced a decrease in these behavior. Otherw ise, rats exposed to acute noise show ed an increase in anxiety-likebehaviors, and rearing in an EE the difference w as even more pronounced.These findings suggest that different noise exposure schedules (either acute or chronic) at an early developmental age might differentiallyaffect behavioral performances. In addition, rearing in an EE improved the performance in associative memory in both schedules w hencompared w ith standard cages. Conversely, opposite results w ere observed betw een both schedules in anxiety-like behavior. Moreover,although no changes w ere observed in habituation memory after either schedule of noise exposure, opposing changes betw een bothschedules w ere found w hen exposed rats w ere reared in an EE.Therefore, it could be concluded that visual, social and physical stimulation during the peri-adolescence period could interact w ith theeffects induced by an earlier exposure to a physical agent such as noise, generating different emotional and behavioral parameters.