Feeding responses to central administration of several somatostatin analogs in chicks

Somatostatin is well known as an inhibitor of growth hormone release from the anterior pituitary. Its effects are exerted via 5 subtypes of receptors, which are named SSTR1 through 5. We recently reported that intracerebroventricular (ICV) injection of somatostatin stimulates feeding behavior in chicks. However, the specific receptors which mediate this orexigenic effect have not been identified in chicks. Thus, the purpose of the present study was to identify the receptor subtypes involved in somatostatin-induced feeding using 5 somatostatin analogs. Chicks that received vapreotide and octreotide (less than 3nmol), which are agonist of SSTR2 and SSTR5, increased their food intake. Additionally, chicks ICV injected with BIM23056 or L-817,818 (SSTR3 and SSTR5 agonists, respectively) also had increased food intake. However, ICV injection of the SSTR4 agonist L-803,087 did not cause an orexigenic effect, suggesting that SSTR4 might not be important in somatostatin-induced feeding behavior. In summary, results from this study may be interpreted as SSTR2, SSTR3 and SSTR5 are related to somatostatin-associated feeding behavior in chicks.