The role of somatostatin and serotonin in the beta-adrenoceptor regulation of gastric function. An experimental study in dogs.

CHAPTER 1. The gastric functions are regulated in a complex manner by the autonomic nervous system, sympathetic and parasympathetic, and hormones and moreover by a system of peptide-containing cells and nerves. The sympathetic influence is mediated by alpha- and beta-adrenoceptors, beta-adrenoceptor agonists in general inhibit the gastric functions. The effects of the beta-adrenoceptors are probably mediated indirectly, and the responsible mechanism may be via release of and endogenous mediator--somatostatin or serotonin. The purpose of the present study, described in the survey, is to examine whether somatostatin or serotonin acts as a mediator for the gastric effects in vivo of beta-adrenoceptor agonists. The proposed mediator must present the following characteristics: A. Inhibitory effects of "physiological" doses in vivo. B. Inhibitory characteristics similar to those of the beta-adrenoceptor agonists. C. A beta-adrenoceptor mediated release. CHAPTER 2. In this chapter the known effects of beta-adrenoceptor agonists on gastric functions (acid secretion, pepsin secretion, antral motility and mucosal blood flow) are presented. The possible mechanisms mediating these effects are mentioned, and the effects of somatostatin and serotonin are reviewed. Beta-adrenoceptor agonists inhibit the acid secretion in vivo in several species, but stimulate in vitro. A similar pattern is probable as for the pepsin secretion, but sufficient results are not available in order to draw a certain conclusion. The antral motility is inhibited both in vivo and in vitro. The mucosal blood flow is increased compared to the acid secretion, however the results points to variable effects depending on the circumstances of the experiments. On the basis of the reviewed effects of somatostatin it is concluded that the effects are inhibitory, but the inhibitory characteristics are not known. A beta-adrenoceptor mediated release of somatostatin has been found, but it has not been examined selectively for the stomach. The gastric effects of serotonin has been sparsely examined and it is not possible to determine the effects as parts of a certain characteristic. It is concluded that neither somatostatin nor serotonin have been examined sufficiently to determine which is the proposed mediator. CHAPTER 3. The materials and methods used are reviewed. Dogs were used and various parameters were measured--acid secretion by titration, pepsin secretion by enzymatic process with haemoglobin as substrate, antral motility by registration of intraluminal pressure, mucosal blood flow by the clearance of neutral red, somatostatin by radioimmunoassay.(ABSTRACT TRUNCATED AT 400 WORDS)