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Atypical beta-adrenoceptors mediating relaxation in the human colon: functional evidence for beta3-rather than

F de Ponti1, C Modini, G Gibelli

  • 1Department of Internal Medicine and Therapeutics, University of Pavia, Piazza Botta, Pavia, I-27100, Italy.

Pharmacological Research
|May 18, 1999
PubMed

Insights

This study investigated beta3-adrenoceptors in the human colon, finding functional evidence for their presence. The results do not support an atypical beta-adrenoceptor distinct from the beta3-subtype.

Area of Science:

  • Pharmacology
  • Gastroenterology
  • Adrenergic Receptor Research

Background:

  • Recent findings suggest a fourth beta-adrenoceptor subtype in adipose and heart tissue.
  • The role of beta3-adrenoceptors in human colonic smooth muscle requires further functional elucidation.
  • Investigating atypical beta-adrenoceptor roles is crucial for understanding receptor pharmacology.

Purpose of the Study:

  • To functionally assess the role of beta3-adrenoceptors in the human distal colon.
  • To investigate the pharmacological profile of beta3-adrenoceptor agonists and antagonists.
  • To determine if an atypical beta-adrenoceptor distinct from beta3 exists in the human colon.

Main Methods:

  • Functional assessment using circular muscle strips of human distal colon.
  • Concentration-effect relationships of beta3-adrenoceptor agonists (CGP12177A, SR59104A) were studied.
  • Effects were examined alone and in the presence of selective beta1/beta2-adrenoceptor antagonists (CGP20712A, ICI118551) and a beta3-antagonist (SR59230A).

Main Results:

  • CGP12177A and SR59104A concentration-dependently relaxed human colonic muscle strips.
  • The relaxant effect of CGP12177A was antagonized by SR59230A, confirming beta3-adrenoceptor involvement.
  • The effects of the agonists were not significantly altered by beta1/beta2-adrenoceptor blockade, and results did not support an atypical beta-adrenoceptor.

Conclusions:

  • Functional beta3-adrenoceptors are present in the human colon.
  • The study provides evidence supporting the beta3-subtype as the primary functional receptor in this tissue.
  • The existence of an atypical beta-adrenoceptor distinct from beta3 in the human colon is not supported by these findings.

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