5-HT3 receptor signaling in serotonin transporter-knockout rats: a female sex-specific animal model of visceral hypersensitivity

Am J Physiol Gastrointest Liver Physiol. 2019 Jan 1;316(1):G132-G143. doi: 10.1152/ajpgi.00131.2018. Epub 2018 Oct 25.


The irritable bowel syndrome (IBS) is a functional gastrointestinal motor and visceral sensation disorder that is more common in women than men. Female serotonin transporter (SERT)-gene knockout (KO) rats exhibit hypersensitivity to colorectal balloon distention (CRD) that mimics colonic hypersensitivity occurring in female IBS patients. Alosetron (5-HT3 receptor antagonist) is used to treat diarrhea-predominant IBS in female patients. Other 5-HT3 receptor antagonists are ineffective at treating IBS symptoms. The visceromotor response (VMR) to CRD in SERT-KO and wild-type (WT) rats was measured following subcutaneous (sc), intracerobroventricular (icv), or intrathecal (it) treatment with 5-HT3 receptor antagonists and an agonist. Alosetron (sc) and granisetron (antagonists) caused a paradoxical increase in the VMR to CRD in SERT-KO female rats. Alosetron (sc) increased the VMR to CRD in WT male rats. Alosetron (it) increased the VMR to CRD in SERT-KO female rats only, and the 5-HT3 receptor agonist SR-52772 increased the VMR to CRD in SERT-KO male rats. Depletion of spinal 5-HT using 5,7-dihydroxytryptamine prevented the increase in VMR to CRD in SERT-KO female and male rats treated it with alosetron and SR-52772, respectively. Alosetron (icv) did not affect the VMR to CRD in WT or KO female rats, but it increased the VMR in male SERT-KO but not WT male rats. These data suggest that 5-HT3 receptor signaling at the dorsal spinal cord mediates visceral hypersensitivity in female SERT-KO rats. Such differences could facilitate development of sex-specific drug treatments for visceral pain. NEW & NOTEWORTHY We studied a model of female sex-specific visceral hypersensitivity using rats that had a loss of function of the serotonin transporter (SERT) caused by gene truncation. Female SERT-KO rats exhibited visceral hypersensitivity in response to colorectal balloon distention. We found that increased 5-HT signaling at dorsal spine 5-HT3 receptors was responsible for visceral hypersensitivity in female but not male SERT-KO rats.

Keywords: 5-hydroxytryptamine receptors; irritable bowel syndrome; serotonin transporter; sex differences; visceral pain.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Carbolines / pharmacology*
  • Disease Models, Animal
  • Humans
  • Hyperalgesia / physiopathology
  • Hypersensitivity / drug therapy
  • Hypersensitivity / genetics*
  • Irritable Bowel Syndrome / physiopathology
  • Rats, Transgenic
  • Receptors, Serotonin, 5-HT3 / drug effects*
  • Receptors, Serotonin, 5-HT3 / metabolism
  • Serotonin / metabolism*
  • Serotonin Plasma Membrane Transport Proteins / drug effects
  • Serotonin Plasma Membrane Transport Proteins / genetics
  • Sex Factors*
  • Visceral Pain / physiopathology


  • Carbolines
  • Receptors, Serotonin, 5-HT3
  • Serotonin Plasma Membrane Transport Proteins
  • alosetron
  • Serotonin