INFLUENCE OF INTRACISTERNAL INJECTION OF SOMATOSTATIN ANALOG RECEPTOR SUBTYPE-2, SUBTYPE-3 AND SUBTYPE-5 ON GASTRIC-ACID SECRETION IN CONSCIOUS RATS

Somatostatin (SST) and its analogs injected into the CSF induce different gastric acid response patterns. Five SST receptors have been characterized (SSTR-1 to -5), We studied the influence of selective SSTR-2, -3 and -5 ligands on basal gastric acid secretion after intracisternal (i,c,) injection in conscious rats equipped with chronic gastric and i.c. cannulae. Compared with pre-injection level, the SSTR-3 agonist, BIM-23056 (1 mu g) increased acid secretion by 274 +/- 43% while the SSTR-2 agonist, DC 32-87 (1 mu g) inhibited acid secretion by 50.7 +/- 13.3%. SST-14 (1 mu g), the SSTR-5 agonist, BIM-23052, (0.5-1 mu g), SSTR-3 (0.5 mu g) and -2 (0.5 mu g) or vehicle injected i.c. did not modify basal acid secretion. These results show that the activation of brainstem SSTR-3 receptors stimulate and SSTR-2 inhibit basal gastric acid secretion in conscious rats with chronic gastric fistulae.