Gastric relaxatory response to insulin before and after vagotomy

Experiments were performed on 4 non-anaesthetized dogs with chronic gastric fistulae, Gastric tonus was studied by volume recording at low pressure head. 0.5 IE insulin/kg bodyweight intravenously was followed by an immediate gastric relaxation, obvious before any marked decrease of blood glucose or plasma potassium occurred, and furthermore not affected by administration of glucose or potassium. This initial relaxation was still present after vagotomy and might be due to transmembraneal metabolic changes upon insulin administration or to direct effect of insulin on gastric smooth smooth muscles. During hypoglycaemia, a second relaxatory phase occurred, and glucose given during this phase temporarily increased gastric tonus, indicating this relaxation to be due to hypoglycaemia. The hypoglycaemic relaxation was markedly reduced but not abolished by vagotomy, indicating also extravagal factors in this response.