Effect of thyrotropin-releasing hormone and atropine on the gastric motility stimulated by insulin-induced hypoglycemia.

The effects of thyrotropin-releasing hormone (TRH) and atropine on the gastric motility after stimulation by insulin-induced hypoglycemia were studied by the intragastric balloon technique. Four healthy young men were examined in two different ways on different days. In one experiment the effect of 50 micrograms TRH, 500 micrograms atropine, and 10 micrograms TRH, all intravenously injected, and in the other 500 micrograms atropine and 50 micrograms TRH were analyzed in this specific sequence. In two subjects the effect of intravenously injected TRH, 200 micrograms, and atropine, 500 micrograms, on the carbacholine-stimulated gastric motility was tested. The hypoglycemic stimulation of the gastric motility was immediately and completely blocked for a period of 9.3 +/- 0.7 min after 50 micrograms TRH and for 3.4 +/- 0.1 min after 10 micrograms TRH. The intragastric basal pressure was immediately reduced in all after TRH injection (-2.5 +/- 0.48 cm H2O pressure). Atropine had no significant effect on the gastric motility after hypoglycemic stimulation. The inhibiting effect of TRH on the carbacholine-stimulated gastric motility was similar to the effect of TRH on the hypoglycemia-stimulated gastric motility. These results demonstrate that TRH effectively inhibits the atropine-resistant stimulation of the gastric motility after insulin-induced hypoglycemia and also has potent relaxing effects on the muscular tonus of the gastric wall.