The influence of the vagus nerve on insulin secretion in the dog has been confirmed by studies involving both vagotomy and vagal stimulation. Following vagotomy, a fall in portal vein insulin levels occurs. Following stimulation of both the right and left vagus, insulin levels rise abruptly, peak within five minutes and rapidly return to baseline levels. A small rise in blood glucose, which occurs simultaneously, cannot be blocked by phentolamine, an alpha-adrenergic blocking agent. When given alone, phentolamine stimulates insulin secretion. Atropine inhibits both the glucose and insulin rises following vagal stimulation. Only a portion of releasable insulin appears to be under vagal control. Glucose mediated insulin release and net glucose utilization are not significantly affected by vagotomy.

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