EFFECTS OF PHARMACOLOGICAL LESION OF ADRENERGIC-INNERVATION OF THE DORSAL VAGAL NUCLEUS ON PANCREATIC INSULIN-SECRETION IN NORMAL AND VAGOTOMIZED RATS

Previous morphological and physiological studies have suggested that t he adrenergic innervation of the dorsal motor nucleus of the vagus ner ve (dmnX) is involved in direct synaptic inhibition of parasympathetic preganglionic neurones of the vagus that control secretion of pancrea tic insulin. We investigated the effects of bilateral 6-hydroxydopamin e (6-OHDA) lesions of adrenergic innervation of the dmnX on pancreatic insulin secretion and glycaemia in normal and vagotomized rats. After two weeks the 6-OHDA lesions produced a marked increase in circulatin g insulin levels, but no change in glycaemia. Hyperinsulinaemia after adrenergic denervation of the dmnX was more pronounced when a glucose bolus was injected intraarterially. Bilateral subdiaphragmatic vagotom y reversed the observed hyperinsulinaemia. This targeted pharmacologic al lesion of the adrenergic innervation of dmnX thus causes hypersecre tion by pancreatic B cells, an effect which requires an intact vagus n erve.