Intracerebroventricular infusion of bombesin modulates GIP secretion in conscious dogs

Glucose-dependent insulinotropic polypeptide (GIP) is an incretin with important role in glucose homeostasis and energy conservation. Thus far, the neural mechanisms involved in the regulation of GIP secretion, have not yet been fully elucidated. The aim of this study was to evaluate a possible effect of intracerebroventricular administration of Bombesin in the regulation of GIP secretion.MethodsThirty-two adult dogs were used in this study. In group 1 the animals received a bolus icv infusion of 200 ng bombesin or an equivalent amount of artificial cerebrospinal fluid (aCSF). In group 2 the animals received a continuous icv infusion of bombesin or aCSF over a 3-h period. In group 3 the experiment of group 2 was repeated with a simultaneous intraduodenal infusion of a glucose load through the Mann–Bollman fistula. Blood samples were taken from cannulation of a hind limb and plasma levels of glucose, insulin and GIP were assayed.ResultsBolus icv infusion of bombesin produced an increase in glucose and GIP levels without a respective increase in plasma insulin levels. Continuous icv infusion and the simultaneous infusion of glucose intraduodenally increased significantly GIP, glucose and insulin levels.ConclusionsIntracerebroventricular levels of bombesin seems to involve in the neural regulation of GIP secretion independently of the presence of nutrients and to potentiate GIP secretion during a glucose load.