Foraging enrichment modulates open field response to monosodium glutamate in mice

BACKGROUND Environmental enrichment can enhance expression of species-specific behaviour. While foraging enrichment is encouraged in laboratory animals, its impact on novelty induced behaviour remain largely unknown. PURPOSE Here, we studied behavioural response of mice to acute and subchronic oral monosodium glutamate (MSG) in an open field with /without foraging enrichment. METHODS Adult male mice, assigned to five groups were administered vehicle (distilled water), or one of four selected doses of MSG (10, 20, 40 and 80 mg/kg) for 21 days. Open field novelty induced behaviours i.e. horizontal locomotion, rearing and grooming were assessed after the first and last doses of MSG. Results were analysed using MANOVA followed by Tukey HSD multiple comparison test and expressed as mean ± S.E.M. RESULTS Following acute MSG administration without enrichment, locomotor activity reduced, grooming increased, while rearing activity reduced at lower doses and increased at higher doses. Subchronic administration without enrichment was associated with increased locomotor activity and reduction in grooming, rearing activity however still showed a biphasic response. Addition of enrichment with acute administration resulted in sustained reduction in locomotor and rearing activities with a biphasic grooming response. Subchronically, there was reduction in horizontal locomotion, biphasic rearing response and sustained increase in grooming activity. CONCLUSION Behavioural response to varying doses of MSG as observed in the open field is affected by modifications such as foraging enrichment, which can reverse or dampen the central effects seen irrespective of duration of administration.