Central factors in the control of insulin and glucagon secretion.

A complete system for neural regulation of insulin and glucagon secretion from the ventral hypothalamus to the autonomic cholinergic and adrenergic nerves of the endocrine pancreas is described. Both physiologic and pathophysiologic states of altered metabolism can be partly explained by activation of this neural system. Direct hypothalamic humoral control of the endocrine pancreas has been evaluated by studies of the hypothalamic hormone somatostatin, or somatotrophin release inhibiting factor (SRIF). Somatostatin has been shown to inhibit pancreatic glucagon and insulin secretion when infused into the pancreatic artery of intact dogs in vivo in the absence of a change of systemic glucose concentration. Although less inhibition is observed when the same amount of hormone is infused intraportally, the potency of somatostatin when given directly into the liver suggests extrapancreatic effects as well as direct pancreatic effects on insulin and glucagon secretion.