Aversive phototaxic suppression (APS) assay is a behavioral assay in which photopositive fruit flies (Drosophila melanogaster) are trained to avoid light using quinine as an aversive stimulus. This conditioned behavior is found to be impaired by sleep deprivation in D. melanogaster. This study tested whether supplementation with Bacopa monnieri can counter this impairment. Three sublethal and effective concentrations of B. monnieri supplement (4.62 × 10−4 g/ ml, 4.62 × 10−3 g/ml, and 4.62 × 10−2 g/ml) were given to test groups of non-sleep-deprived (slp+) and sleep-deprived (slp−) flies subjected to the APS assay. The extent of learning and short-term memory (STM) retention was based on average pass rates (APRs) defined as the number of trials that each fly exhibited a photonegative response before and after conditioning. B. monnieri supplement improved the APR of both slp+ and slp− flies as compared to the unsupplemented flies. These effects were found to be dose-dependent from the low- to the mid-level (4.62 × 10−4 g/ml to 4.62 × 10−3 g/ml) concentrations of the supplement on D. melanogaster learning and STM retention. Supplementing fly food with B. monnieri improved learning and STM of slp− flies with learning and STM deficits caused by sleep deprivation. The slp− flies given B. monnieri supplementation had higher learning rates and longer STM retention than slp+ flies without B. monnieri supplementation. Unexpectedly, slp− flies given B. monnieri supplementation had the same learning and STM retention levels as slp+ flies also given B. monnieri supplementation. Bacopa monnieri supplementation enhances both the learning capacities and the STM retention of both non-sleep-deprived and sleep-deprived fruit flies. Advantageous effects were dose-dependent for both learning and STM retention.
Key words: aversive phototaxic suppression, Drosophila melanogaster, Bacopa monnieri, short-term memory, sleep deprivation
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