NEURAL MONITORING-SYSTEM FOR CIRCULATING SOMATOSTATIN IN THE HEPATOPORTAL AREA

If a peptide hormone secreted from the gastroenteropancreatic (GEP) sy stem is monitored by the hepatic vagal nerve, the nerve can signal the central nervous system and thereby exert control on its target organs . In this review, we offer a line of evidence for the hypothesis. When a physiological dose of somatostatin (SS), one of the GEP hormones, w as injected into the rat portal vein, the spike discharge rate in the hepatic afferent vagus increased significantly. This SS-induced activa tion of the vagus was completely abolished by a prior administration o f our monoclonal antibody to SS receptor into the portal vein. We furt her disclosed a morphological basis for this neural reception to SS in the hepatoportal area: the neural bodies, located beneath the endothe lium of the rat portal vein, preferentially bound the exogenous SS inj ected intraportally as revealed immunohistologically. The bodies conta ined a structure of the nerve fiber arborizations resembling those of the afferent apparatus of Krause, on which the presence of SS receptor was confirmed histochemically using the anti-SS receptor antibody. Th ese results provide a new insight into the receptor-mediated neural re ception to GEP hormones in the hepatoportal area, implying the potenti al role of the reception in the GEP physiology. (C) Elsevier Science I nc. 1997.