Reflex hypoglycemia initiated by insulin.

The injection of a bolus of insulin (40 millimicrons) in the coeliac trunk in anesthetized rabbits elicits an immediate rapid rise of arterial IRI. Inferior vena cava and jugular glucose levels drop precipitously 2 min after insulin injection, increasing the A-V glucose difference. The same amount of insulin injected via the coeliac trunk in abdominal-vagotomized rabbits, failed to induce any significant changes in venous glucose concentration and A-V glucose, although there was a similar rise of IRI concentration in arterial plasma. Electrical stimulation of the central stump of the abdominal vagi does not alter the IRI levels in arterial plasma, however, arterial blood glucose increases suddenly, venous blood glucose drops in the first 2 min of stimulation and the A-V glucose difference increases; there are no significant changes in blood flow, arterial pressure and oxygen saturation in cephalic circulation. These data suggest that small amounts of insulin injected or secreted in a zone irrigated by the coeliac trunk, trigger a hypoglycemic reflex. Evidence is provided to suggest that this is by causing a rapid increase in glucose both by the brain and leg muscle mass.