Autonomic nervous control of the endocrine secretion from the isolated, perfused pig pancreas

Abstract

The effect of electrical stimulation of the splanchnic and the vagus nerve supply to isolated, perfused pig pancreas on the secretion of insulin, glucagon and pancreatic polypeptide (PP) was investigated. Functional integrity of the autonomic nerve supply was assessed by the effect of nerve stimulation on vascular resistance and exocrine secretion. Splanchnic nerve stimulation increased glucagon and PP output (2 to 3-fold) and inhibited insulin output (by 42%). Propranolol abolished the effect on PP and glucagon secretion, but did not affect the inhibition of insulin secretion. Phenoxybenzamine abolished the inhibition of insulin secretion, reduced the effect on glucagon secretion and enhanced the effect on pancreatic polypeptide secretion. Combined α- and β-adrenergic blockade abolished all effects of splanchnic nerve stimulation. Vagus nerve stimulation increased the secretion of all 3 hormones (PP: up to 30-fold, insulin and glucagon: 3 to 5-fold). The effect on insulin and PP-secretion was mimicked by acetylcholine at 10 −7−10 −6 M, whereas glucagon secretion was inhibited. The effect of vagus nerve stimulation on insulin and PP secretion was augmented by physostigmine, and inhibited (but not abolished) by atropine at 10 −7−10 −6 M. The effect on glucagon secretion was inhibited by physostigmine and unaffected by atropine. It is concluded that all of the effects of splanchnic nerve stimulation on insulin and PP secretion can be explained by interactions of norepinephrine with excitatory β-receptors on PP-cells and inhibitory receptors on the insulin cells. Both cell types are also stimulated via muscarinic cholinoceptors, but the partial atropine resistance suggests that other transmitters participate in vagal activation. The nervous regulation of glucagon secretion is complex and may involve the peptidergic innervation of the pancreatic islets.