Stress-induced changes in dietary amino acid preferences and 5-HT2A receptor gene expression in acute and chronic...

Deficiencies in neurotransmitter precursors are associated with stress and depression. This study evaluated amino acid preferences in rats subjected to acute and chronic stress, along with the gene expression of the serotonin receptor 5-HT2A (5-HT2AR) in the basolateral amygdala (BLA) of rats to assess the detrimental effects of stress on them.

Seventy adult male Wistar rats were used in behavioral and molecular experiments. The forced swimming test (FST) and chronic unpredictable stress (Cus) protocols were employed to induce acute and chronic stress. For both experiments, the animals were randomly divided into five groups (n = 7): Control, acute stress (As), As + fluoxetine, Cus, and Cus + fluoxetine. Amino acid preferences, including tryptophan, tyrosine, and histidine, were assessed. Moreover, 5-HT2AR expression in the BLA was evaluated using real-time PCR.

Chronic stress produced a pronounced increase in total food intake (approximately two-to-three-fold relative to controls). In contrast, acute stress elicited a strong, and specific preference for tyrosine-enriched food, which accounted for the majority of total intake, while consumption of tryptophan- and histidine-enriched diets was markedly reduced. Administration of fluoxetine greatly reduced overall food intake and altered amino acid preferences in both stress models. Gene expression of 5-HT2AR was markedly elevated in both stress groups, an effect that was completely reversed by fluoxetine treatment. Dietary amino acids preference and 5-HT2AR expression may be involved in the pathophysiology of depression. These findings may inform future preventive or therapeutic interventions.