Pharmacological modulation of postprandial colonic motor activity in the pony.

The research article discusses a study on the effect of various drugs on the post-meal activity of the large intestine in horses. Specifically, the study investigated the role of cholinergic stimulation in the gastrocolonic reflex, and the impact of bethanechol and PGF2 alpha on said reflex.

Overview of Research

• The researchers were interested in understanding the activity of the large intestine in horses post meals, which they term as ‘gastrocolonic reflex’.
• They monitored the contractile activity of the large intestine and found a two-phase response to feeding: enhancement of migrating complexes (a specific pattern of contractions) passing through the colon and an increase in smooth muscle cyclic variations in a designated region of the colon (left ventral colon).

Effect of Drugs on Colonic Motor Activity

• The study used the cholinergic agonist, bethanechol (a type of drug that mimics the neurotransmitter, acetylcholine), and found that it induced similar patterns of contractile activity as seen post meals.
• Prostaglandin F2 alpha (PGF2 alpha, a compound involved in muscle contraction), was administered through intra-arterial infusion. This increased the contractile activity during infusion, but did not create distinct patterns of activity.

Role of Cholinergic Stimulation

• The study then involved the use of the drug atropine which could prevent the effects of post-meal, cholinergic and PGF2 alpha stimulation of colonic motility. However, other drugs like indomethacin or flunixin did not show the same effects.
• This implied that the gastrocolonic reflex mainly involved cholinergic stimulation (activation by substances that behave like acetylcholine).
• Thus, the research concluded that cholinergic stimulation of the caecum (beginning of the large intestine) and the replicated colon is critical in the post-meal reflex, including the excitatory effects of prostaglandin F2 alpha.