Biphasic disruption of fasting equine gut motility by dopamine–a preliminary study.

This study explores the impact of dopamine on the gut motility of fasting horses. The researchers found that dopamine, when administered intravenously, resulted in a two-part disturbance to gut motility, initially inhibiting movement in the stomach and later causing irregular activity in the stomach and small intestine long after the dopamine infusion was interrupted.

Methodology

• The study involved intravenous infusion of dopamine at different dosages (1,5 and 10 micrograms/kg/min) to three fasted ponies for a period of one hour.
• The researchers observed changes in both heart rate and gut motility in order to determine the effects of such dopamine administration.

Results

• The infusion resulted in a dose-dependent increase in heart rate which began and ended quickly at the start and end of the infusions, respectively.
• It also caused dose-dependent changes in gastric and small intestinal motility, manifested in two distinguishable phases.
• During the first phase, there was a significant reduction in the amplitude of gastric contractions.
• The second phase saw an extended period of activity in the stomach and irregular activity in the small intestine.
• The period between successive phase IIIs in the small intestine also increased markedly.
• The left dorsal colon and small colon displayed variable responses to the dopamine infusion.

Conclusion

• This study concludes that Dopamine disrupts the normal fasting motility pattern in horses in a biphasic manner.
• Initially, it inhibits the stomach’s activity, but this is followed by a period of increased activity in both the stomach and small intestine, similar to the motility pattern observed post-meal.
• While the cardiovascular effects of the dopamine were temporary, the alterations in gastrointestinal motility persisted long after the dopamine infusion was terminated.