It is well known that a prolonged period of fasting produces, in normal subjects, a “diabetic-like” condition manifested by glucose intolerance and diminished insulin secretion. Administration of the alpha adrenergic blocking agent, phentolamine (Regitine), to healthy fasting subjects caused hyperinsulinemia in response to an intravenous glucose load without amelioration of glucose intolerance. These observations indicate that (1) reversal of hypoinsu-linemia does not acutely alter those factors which cause fasting glucose intolerance, and (2) the increase in sympathetic tone observed during starvation is responsible for the suppression of insulin release. The latter suggests that the autonomic nervous system plays an important physiological role in the regulation of the glucose-insulin axis.

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