The nervous control of rat glucagon secretion in vivo

In order to study the efferent pathways of the nervous regulation of rat A and B cells, portal blood samples were obtained in vivo without interruption of the blood flow. Glucagon, insulin and catecholamines were determined and hepatic blood flow (EHBF) was estimated by a Brome-Sulfone-Phtaleine extraction method. Carotid blood pressure was monitored and a normal volaemia was maintained. Stimulation of the right vagus nerve increased EHBF and the releases of glucagon and insulin. Stimulation of splanchnic nerve increased the glucagon and catecholamine secretions and decreased that of insulin. Acute hypovolaemia as induced by blood withdrawal, caused hormonal consequences similar to those of splanchnic stimulation. It is suggested that the nervous control of pancreatic islets plays an important role in the rat species. Assessment of the haemodynamic status is critical for the valid interpretation of pancreatic hormone concentrations in experimental conditions. A sympathetic stimulation can account for the high glucagon and relatively low insulin secretions which characterize the hormonal pattern of stress.