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The obestatin/ghrelin system as a novel regulatory mechanism of iris muscle contraction

A Rocha-Sousa1, F Falcão-Reis, A F Leite-Moreira

  • 1Laboratory of Physiology, Faculty of Medicine, University of Porto, Portugal. arsousa@med.up.pt

Current Eye Research
|January 25, 2008
PubMed
Abstract

Insights

Obestatin enhances iris sphincter muscle contraction and relaxes iris dilator muscles. Ghrelin, however, reduced basal tension in the iris sphincter and electrical field stimulation-elicited contractions.

Area of Science:

  • Ophthalmology
  • Endocrinology
  • Pharmacology

Background:

  • Obestatin and ghrelin are peptide hormones with diverse physiological roles.
  • Their specific effects on ocular tissues, particularly iris muscles, remain largely unexplored.

Purpose of the Study:

  • To investigate the impact of obestatin and ghrelin on iris muscle contractility.
  • To determine the influence of these hormones on basal tension and agonist-induced contractions in rabbit iris sphincter and dilator muscles.

Main Methods:

  • Isolated rabbit iris sphincter and dilator muscles were utilized.
  • Carbachol and epinephrine were used to elicit muscle contractions.
  • Electrical field stimulation (EFS) was employed to assess sphincter muscle response.
  • The effects of obestatin and ghrelin (10⁻⁵ M) on muscle tension were evaluated.

Main Results:

  • Obestatin potentiated carbachol-induced contractions of the iris sphincter by 19.0%.
  • Ghrelin decreased basal tension of the iris sphincter by 21.7% and EFS-elicited contractions by 9.3%.
  • Obestatin decreased basal tension of the iris dilator by 14.1% and did not affect epinephrine-induced contractions.

Conclusions:

  • Obestatin enhances cholinergic contractions in the iris sphincter.
  • Obestatin exhibits a relaxing effect on iris dilator muscles.
  • Ghrelin demonstrates a complex modulatory role on iris sphincter function.

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