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Age and segmental differences in 5-hydroxytryptamine-induced hypersecretion in the pig small intestine
M L Grøndahl1, M B Hansen, I E Larsen
1Department of Anatomy and Physiology, Royal Veterinary and Agricultral University, Frederiksberg, Denmark.
Summary
The secretory response to 5-hydroxytryptamine in pig small intestine diminishes with age and as it moves down the intestine. This age-related and directional decrease may explain reduced cholera toxin responses.
Area of Science:
- Gastroenterology
- Physiology
- Pharmacology
Background:
- 5-Hydroxytryptamine (serotonin) is a key mediator in cholera toxin-induced intestinal hypersecretion.
- Understanding age- and segment-dependent responses to secretagogues is crucial for pediatric and adult gastroenterology.
Purpose of the Study:
- To investigate the hypothesis that 5-hydroxytryptamine-induced hypersecretion in the pig small intestine decreases with increasing age and in an aboral direction.
- To correlate in vivo and in vitro findings regarding 5-hydroxytryptamine's secretory efficacy.
Main Methods:
- In vivo studies using ligated intestinal loops in pigs (neonates, young, adults) to measure fluid accumulation.
- In vitro studies using Ussing chambers to measure short-circuit current in intestinal segments from pigs of different ages.
- Segmental analysis in young pigs to assess in vivo and in vitro responses along the jejunum and ileum.
Main Results:
- In vivo, 5-hydroxytryptamine efficacy significantly decreased with age (23% in young, 63% in adults vs. neonates) and aborally (22% mid-gut, 56% distal vs. proximal).
- In vitro, efficacy also decreased with age (30% young, 57% adults vs. neonates) but showed an unexpected increase in the distal segment (56% vs. proximal).
- In vivo and in vitro results indicate a general trend of reduced secretory response to 5-hydroxytryptamine with increasing age and aboral progression.
Conclusions:
- The secretory response to 5-hydroxytryptamine in the pig small intestine declines with age and in the aboral direction, primarily based on in vivo data.
- This age- and directional decrease in sensitivity to 5-hydroxytryptamine likely contributes to the reduced secretory response observed with cholera toxin in older pigs and more distal segments.