Smooth muscle electromyographic measurements with pigs in a stress model

Stress adversely affects physiological processes in animals, including gastrointestinal motility, potentially reducing digestion efficiency. Electromyography (EMG) is a suitable method for monitoring smooth muscle activity, allowing separate measurements of the heart and digestive organs (stomach, small intestine, large intestine). This study aimed to investigate whether stress alters the smooth muscle activity of the digestive tract using electromyographic measurements. We conducted the experiment on Topigs x Duroc barrows (n = 4), weighing 30 kg. Stress induction was performed with a single intravenous ACTH injection (10 µg/kg), which dose corresponds to a mild stress effect. Electromyographic signals were continuously recorded for 8 hours both in control and stress conditions. The measurements were divided into 30-minute intervals, and the smooth muscle electric potential (mV) was determined for each organ. Statistical comparisons between control and stress-induced states were made using paired Student's t-test. The results revealed a post-stress reduction in smooth muscle activity across all organs. The decrease was statistically significant in the small and large intestine, while in the stomach, reduced activity was observed 5 hours after stress induction. In conclusion, even mild stress decreases the smooth muscle activity of digestive organs, reducing gastrointestinal motility and potentially impairing digestion efficiency.