Dual role of dietary tryptophan on memory regulation in male albino wistar rats - synergistic modulation of serotonergic signaling and kynurenine pathway.

OBJECTIVE

This study investigates the impact of tryptophan metabolism on synaptic plasticity, neurogenesis, and memory consolidation using a combined biochemical and behavioral approach.

METHODS

We treated male Albino Wistar rats with different doses of tryptophan for 4 weeks followed by weekly assessment of memory performance through Morris Water Maze (MWM) and Novel Object Recognition (NOR) tests. High-performance liquid chromatography (HPLC) was used to quantify serotonin and metabolites in hippocampus, while kynurenine in plasma samples.

RESULTS

Our findings reveal that low dose of tryptophan improved learning and memory in rats while high dose significantly impaired spatial and recognition memory, correlating with reduced serotonin and increased kynurenic acid levels. Conversely, tryptophan supplementation at high dose was also accompanied by increased Interleukin-6 (IL-6), Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) expression in brain.

DISCUSSION: These results highlight the dual role of tryptophan in memory regulation - through serotonergic signaling and kynurenine pathway modulation - providing potential therapeutic targets for memory-related disorders such as Alzheimer's and Parkinson's-related dementia.