Evidence for visceral hypersensitivity in high-anxiety rats.

In patients with irritable bowel syndrome, anxiety is often associated with visceral pain. Based on this information we hypothesized that rats genetically predisposed to anxiety have an increased visceral sensitivity. To test this hypothesis, visceromotor reflex recordings in response to colorectal distention were used to estimate the level of visceral stimulation in high; moderate-, and low-anxiety rats. We compared the effect of innocuous colorectal distension in rats with and without sensitized colons. In nonsensitized rats visceromotor responses were increased by colorectal distention with the greatest response in the high-anxiety Wistar-Kyoto strain. Sensitization of the colon significantly increased visceromotor responses to colorectal distention in all rat strains. In summary, our data suggested that a manifestation of a genetically determined anxiety level appeared to be abnormal neural responsiveness of the gastrointestinal tract leading to visceral hypersensitivity in high-anxiety animals.