Action of opiates on gastrointestinal function.

Area of Science:

• Gastroenterology
• Neuroscience
• Pharmacology

Background:

• Opioid peptides and receptors are present throughout the gastrointestinal (GI) tract.
• Peripheral opioid release suggests a role in modulating GI motor and secretory functions.

Purpose of the Study:

• To investigate the role of opioid peptides and receptors in controlling GI motility and secretions.
• To elucidate the differential effects of various opioid receptor subclasses on gut functions.

Main Methods:

• Review of animal and human studies on opioid effects on GI tract.
• Analysis of receptor subclass involvement (mu, delta, kappa) in opioid actions.
• Examination of central and peripheral mechanisms of opioid influence on gut.

Main Results:

• Mu agonists primarily inhibit gastric motility and delay emptying via central action.
• Opioids affect intestinal transit differently across species, influencing contractions.
• Morphine stimulates colonic motility in humans, affecting tonic contractions and transit.
• Delta and mu receptors stimulate colonic motility, while kappa receptors inhibit it (centrally).
• Opioids reduce pancreatic and intestinal secretions through central and enteric nervous system actions.

Conclusions:

• Opioid peptides play a significant physiological role in regulating gut motility and secretions.
• These actions explain the pharmacological effects of opiates on the digestive system.