Prokinetic effects of cisapride, naloxone and parasympathetic stimulation at the equine ileo-caeco-colonic junction.

This study examines the effects of different drugs and chemical compounds on the movement of the ileo-caeco-colonic junction in horses. The results indicate that cisapride and naloxone stimulate productive movements in this area, while the effects of other tested substances vary.

Research Methodology

In this study, the researchers recorded the electromyogram (a record of the electrical activity of muscles) of the terminal ileum, the caecum, and the proximal right ventral colon of fasted, conscious ponies. These horses received equiactive doses of several substances including:

• pilocarpine and carbachol, both analogues of acetylcholine (a neurotransmitter that helps pass signals in the nervous system),
• cisapride and metoclopramide, both stimulants for acetylcholine release from myenteric neurons (nerve cells located in the gastrointestinal tract),
• naloxone, an antagonist of the endogenous inhibitory opioid system (it blocks the opioid receptors and is often used to treat opioid overdoses).

Findings

The study found that cisapride and naloxone induced typical migrating spike bursts (periods of intense muscle activity) in the colon. These were associated with contractions of the body and the base of the horses’ caecum (the first section of the large intestine).

Both pilocarpine and carbachol stimulated the terminal ileum (the final section of the small intestine) but had contrasting effects on the caeco-colonic segment: pilocarpine decreased its activity, while carbachol increased it.

High doses of metoclopramide showed weak and non-specific stimulatory motor effects.

Conclusion

The research concluded that for a true prokinetic effect (that enhances gastrointestinal motility) at the equine ileo-caeco-colonic junction, a motor profile involving coordination between contractions of the body and base of the caecum and migrating spike bursts on the proximal colon is needed.

These changes in the motor profile were notably achieved by cisapride and naloxone. Carbachol promotion was lesser in comparison.
This points to potential courses of treatment for horses dealing with digestive health issues aimed at stimulating productive movement in the ileo-caeco-colonic junction.