title: Postnatal development of the serotonin signaling system in the mucosa of the guinea pig ileum.
abstract: BACKGROUND
  Serotonin is an important neurohumoral molecule in the gut but its signaling system is not fully developed in the neonatal gastrointestinal (GI) tract. This study aimed to evaluate the postnatal maturation of serotonin signaling in the small intestine.
  
  
  METHODS
  In vitro amperometry for real-time measurement of serotonin at the mucosal surface, immunoblot, immunohistochemistry and high-performance liquid chromatography (HPLC) were used to examine serotonin handling in ileal segments from guinea pigs of different ages.
  
  
  RESULTS
  Extracellular serotonin levels significantly declined over the first three postnatal weeks, after which the levels increased and reached their maximum at 9 weeks postnatally. Serotonin levels were insensitive to the inhibition of the serotonin transporter (SERT) until the animals reached 3 weeks old. Measurement of serotonin and its metabolite 5-hydroxyindole acetic acid (5-HIAA) in the mucosa revealed that the serotonin turnover was significantly lower in neonates. Immunoblot and immunohistochemistry showed that SERT expression was extremely low in the neonatal period. Serotonin staining in cross-section showed that enterochromaffin (EC) cells were preferentially localized in the crypt region in neonates and the number of EC cells was significantly higher in 9-week-old animals.
  
  
  CONCLUSIONS
  SERT expression is low in the neonatal intestine and serotonin signaling matures postnatally. Extracellular serotonin levels decrease during the first three neonatal weeks as SERT expression increases. Extracellular serotonin levels increase after 3 weeks (weaning) possibly due to an increase in EC cell numbers. Postnatal maturation of serotonin signaling coincides with dietary changes in the developing guinea pig.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, MI 24423, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhao
authors.forename: I
authors.initials: I
authors.lastname: Sovadinova
authors.forename: V M
authors.initials: VM
authors.lastname: Swope
authors.forename: G M
authors.initials: GM
authors.lastname: Swain
authors.forename: M M
authors.initials: MM
authors.lastname: Kadrofske
authors.forename: X
authors.initials: X
authors.lastname: Bian
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D002452:Cell Count; D004759:Enterochromaffin Cells / Q000166:cytology / Q000378:metabolism; D006168:Guinea Pigs; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007082:Ileum / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D008839:Microelectrodes; D023421:Models, Animal; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D050486:Serotonin Plasma Membrane Transport Proteins; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid