Behavioral, Hormonal, and Serotonergic Responses to Different Restricted Feeding Schedules in Rats

To determine the effect of long-term restricted feeding schedules on behavior. serotonergic responses, and neuro-endocrine functions, metabolism of serotonin (5-HT) in the striatum, expression of serotonin-1A (5-HT1A) auto-receptor in the raphe nuclei and circulating levels of leptin and corticosterone were determined in female Wistar rats kept on excessive food restriction schedule. Due to a role of dietary deficiency of tryptophan (Trp) in influencing serotonergic neurotransmission. circulating levels of Trp were also determined. Estimations were done in 2 different restricted feeding models: time-restricted feeding (TRF) and diet restricted (DR). TRF animals were given access to food ad libitum only for 2hours/day. The DR animals were given a small calculated amount of food each day. We found that chronic food restriction for 5 weeks cause a significant decrease in the body weight and produced hyperactivity in both. TRF and DR animals. Levels of Trp were declined in circulation and in the striatum. Similarly, the levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIM) were decreased in the striatum. Also, the expression of 5-HT1A auto-receptor was declined in the raphe nuclei. These changes in 5-HT metabolism and 5-HT1A auto-receptor expression were more profound in DR animals as compare to TRF animals. Similarly. hypoleptinemia and increased corticosterone found in both models was higher in DR animals. Effect of dietary deficiency of Trp in the modulation of striatal 5-HT metabolism and its consequences on circulating leptin and corticosterone are discussed.

Automated summary

This study investigated the effects of long-term restricted feeding schedules on behavior, serotonergic responses, and neuro-endocrine functions in female Wistar rats. The results showed that chronic food restriction led to decreased body weight and increased hyperactivity in both time-restricted feeding and diet restricted animals. Levels of tryptophan (Trp), serotonin (5-HT), and its metabolite 5-hydroxyindoleacetic acid (5-HIM) were decreased in the circulation and striatum. The expression of serotonin-1A (5-HT1A) auto-receptor in the raphe nuclei was also decreased. These changes were more significant in the diet restricted animals. Hypoleptinemia and increased corticosterone levels were observed in both models, with greater effects in the diet restricted animals. The study highlights the importance of dietary deficiency of Trp in modulating 5-HT metabolism and its impact on circulating leptin and corticosterone.