Circadian Regulation of Serotonin in the Gut
Abstract: Circadian oscillators distributed throughout the body regulate the timing of physiological functions, including hormone production and gut motility. Enteric serotonin is one such hormone and is associated with multiple functional bowel disorders such as irritable bowel disease and Crohn’s disease. In the chronobiological literature, daily restricted feeding (DRF) is demonstrated to phase shift gastrointestinal motility, however its effects on enteric serotonin (5-HT) are not well characterized. This study aimed to investigate the effects of DRF on putative 5-HT rhythm.
C57BL/6 mice placed on a progressively restricted feeding regime were compared to a control group placed under ad libitum feeding conditions and were assessed under both LD (12:12 light dark cycle) and conditions of constant darkness (DD) conditions. After the third day of DD, the mice were sacrificed and serum and tissues were harvested. Motility was assessed by counting and weighing fecal samples ELISA was performed on serum samples to assess serotonin (5-HT) levels.
Preliminary results suggest that the progressive restricted feeding regime (PRF) does not entrain the motility of the gut under LD conditions. Whereas the abrupt feeding regime phase shifted the motility rhythm in the RF mice, the progressive regime appeared to disrupt the rhythm but had no effect on the phase In contrast to some reports in the literature, we detected no rhythm of serotonin abundance in serum in any of the experimental groups. However high levels of variability in serotonin levels between samples may necessitate further biological replication in order to detect any such rhythm.
Kimberly J. Baker* and Stephen P. Karaganis
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