Evaluation of short-term memory in monosodium glutamate-fed fruit flies (Drosophila melanogaster) using adverse phototaxic suppression.

Abstract

Aversive phototaxic suppression (APS) is a behavioral assay in which fruit flies (Drosophila melanogaster) are repeatedly trained to avoid light by associating it with an aversive stimulus (quinine). In this study, the assay was used to test the effect of increasing food medium concentration of monosodium glutamate (MSG) on short-term memory (STM) formation in adult flies. To assess potential MSG impact on STM retention as well, three extension protocols were evaluated based on their capacity to measure one-hour memory performance. Results indicate that MSG adversely affected STM in a dosedependent manner, and its formation (at threshold dose between 0.5 mM and 5 mM) was more hampered than its retention (at threshold dose between 5 mM and 50 mM). The negative effect of the compound in Drosophila cognition observably occurs only upon reaching minimum effective concentration levels, suggesting that such disruption may be avoided through MSG intake dose regulation.