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. 2019 Nov 4;318(1):G130–G143. doi: 10.1152/ajpgi.00173.2019

Fig. 2.

Fig. 2.

Changes in the enteric nervous system (ENS) and intestinal epithelium in mice with the serotonin reuptake transporter (SERT) Ala56 mutation compared with mice exposed developmentally to fluoxetine. SERT Ala56 mice have a hyperfunctional SERT that enhances the rate of serotonin (5-hydroxytryptamine, 5-HT) reuptake and thus inactivation, leading to a decrease in the amount of 5-HT neurotransmission. This results in a hypoplastic ENS, with deficits in total and late-born neurons, slower ex vivo gastrointestinal (GI) motility, and shorter intestinal villus height when compared with wild-type mice. In contrast, fluoxetine exposure during development results in an increase in 5-HT neurotransmission, a hyperplastic ENS, faster ex vivo GI motility, and taller intestinal villi compared with vehicle-exposed mice. Of note, tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme responsible for 5-HT synthesis in the ENS, whereas TPH1 is the rate-limiting enzyme responsible for 5-HT synthesis in the intestinal epithelium. 5-HIAA, 5-hydroxyindoleacetic acid; 5-HTP, 5-hydroxytryptophan; AADC, amino acid decarboxylase; MAO, monoamine oxidase; SSRI, serotonin reuptake inhibitor; Trp, tryptophan.