Central nervous system action of bombesin: mechanism to induce hyperglycemia.

Bombesin acts within the brain to produce a prompt and sustained hyperglycemia, hyperglucagonemia, and relative or absolute hypoinsulinemia. Bombesin does not decrease plasma glucose turnover. Acute adrenalectomy but not hypophysectomy prevents hyperglycemia and hyperglucagonemia after intracisternal administration of bombesin. Administration of bombesin into the lateral ventricle of awake, unrestrained animals results in elevation of plasma glucose, preceded by a significant increase in plasma epinephrine and no increase in plasma norepinephrine or dopamine. Systemic administration of somatostatin prevents bombesin-induced hyperglycemia and hyperglucagonemia. These data support the conclusion that bombesin acts within the brain to increase sympathetic outflow resulting in increased adrenalmedullary epinephrine secretion, followed by depression of plasma insulin and elevation of plasma glucagon and glucose.