Myoelectrical and mechanical activity of stomach and intestine in hypothyroid dogs.

Myoelectrical activity was studied in normothyroid and hypothyroid Labrador dogs in the resting state, following injection of pentagastrin, bethanechol chloride, and after feeding. Hypothyroidism was produced by total thyroidectomy and chronic treatment with thiouracil. Electrodes were surgically implanted over the serosa of the stomach, duodenum, jejunum, and ileum and used for repeated recording of myoelectrical activity of gastrointestinal muscles. A strain gauge was implanted over the gastric antrum and served to record mechanical activity of the stomach. As compared with control dogs, hypothyroid animals showed (a) decreased frequency of electrical control activity of the stomach and jejunum, (b) decreased occurrence of electrical response activity (spike potentials) following stimulation, and (c) decreased mechanical response to the same stimulants, ie, pentagastrin, bethanechol chloride, and food.