Adrenergic innervation of the dorsal vagal motor nucleus: possible involvement in inhibitory control of gastric acid and pancreatic insulin secretion |
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Authors: | P. Siaud R. Puech I. Assenmacher G. Alonso |
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Affiliation: | (1) Laboratoire de Neurobiologie Endocrinologique, URA 1197 CNRS, Université de Montpellier II, Montpellier, France;(2) Laboratoire de Pharmacologie et Pharmacodynamie, URA 85 CNRS, Université de Montpellier I, Montpellier, France;(3) Laboratoire de Neurobiologie Endocrinologique, Université des Sciences et techniques du Languedoc, Place E. Bataillon, F-34060 Montpellier cedex, France |
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Abstract: | Summary Morphological and physiological approaches were used to investigate the possible role of an adrenergic innervation of the dorsal vagal complex in the control of basal gastric acid and pancreatic insulin secretion in the rat. The use of retrograde-tracing methods with injections of True Blue or of wheat-germ agglutinin into the stomach or pancreas first confirmed that most vagal preganglionic neurons innervating these two viscera are localized in the dorsal motor nucleus of the vagus, a number of them connected to both viscera. Light- and electron-microscopic investigation of the organization of adrenergic neuronal structures immunoreactive to phenylethanolamine-N-methyltransferase within this medullary nucleus further revealed: (i) that adrenergic axons establish profuse synaptic connections of the symmetrical type with perikarya and dendrites of this nucleus, and (ii) that several of these adrenergic fibers are connected with retrogradely labeled neurons innervating the stomach and/or pancreas. Lastly, measurements of basal gastric acid output and plasma insulin clearly indicated that both visceral secretions are rapidly and conspicuously decreased by local infusion of 2 nM adrenaline within the dorsal vagal complex. Taken together, these data strongly suggest that the adrenergic innervation of the dorsal medulla oblongata is involved in direct synaptic inhibition of the parasympathetic preganglionic neurons of the vagus that control secretion of gastric acid and pancreatic insulin. |
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Keywords: | Adrenaline Medulla oblongata Parasympathetic nervous system Rat (Sprague-Dawley) |
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