Cholecystokinin receptor antagonism of stimulated pancreatic and gastric secretion

Nesfatin-1 inhibits gastric acid secretion via a central vagal mechanism in rats

Nesfatin-1, a novel hypothalamic peptide, inhibits nocturnal feeding behavior and gastrointestinal motility in rodents. The effects of nesfatin-1 on gastrointestinal secretory function, including gastric acid production, have not been evaluated. Nesfatin-1 was injected into the fourth intracerebral ventricle (4V) of chronically cannulated rats to identify a nesfatin dose sufficient to inhibit food intake. Nesfatin-1 (2 μg) inhibited dark-phase food intake, in a dose-dependent fashion, for >3 h. Gastric acid production was evaluated in urethane-anesthetized rats. Nesfatin-1 (2 μg) was introduced via the 4V following endocrine stimulation of gastric acid secretion by pentagastrin (2 μg·kg(-1)·h(-1) iv), vagal stimulation with 2-deoxy-D-glucose (200 mg/kg sc), or no stimulus. Gastric secretions were collected via gastric cannula and neutralized by titration to determine acid content. Nesfatin-1 did not affect basal and pentagastrin-stimulated gastric acid secretion, whereas 2-deoxy-D-glucose-stimulated gastric acid production was inhibited by nesfatin-1 in a dose-dependent manner. c-Fos immunofluorescence in brain sections was used to evaluate in vivo neuronal activation by nesfatin-1 administered via the 4V. Nesfatin-1 caused activation of efferent vagal neurons, as evidenced by a 16-fold increase in the mean number of c-Fos-positive neurons in the dorsal motor nucleus of the vagus (DMNV) in nesfatin-1-treated animals vs. controls (P < 0.01). Finally, nesfatin-induced Ca(2+) signaling was evaluated in primary cultured DMNV neurons from neonatal rats. Nesfatin-1 caused dose-dependent Ca(2+) increments in 95% of cultured DMNV neurons. These studies demonstrate that central administration of nesfatin-1, at doses sufficient to inhibit food intake, results in inhibition of vagally stimulated secretion of gastric acid. Nesfatin-1 activates DMNV efferent vagal neurons in vivo and triggers Ca(2+) signaling in cultured DMNV neurons.

Effect of CCK receptor antagonist on growth of pancreatic adenocarcinoma

Cholecystokinin (CCK) exerts an influential effect on the growth of normal pancreas. It is postulated that carcinoma arising from the pancreas may retain some normal pancreatic properties as far as hormone dependency is concerned. In an effort to examine the effect of CCK on the growth of pancreatic cancer, we evaluated the effect of CCK receptor antagonist on the growth of a transplantable adenocarcinoma of the pancreas. For this study we utilized three groups of hamsters with adenocarcinoma of the pancreas transplanted subcutaneously on the right flank. Group I (n = 15) served as control. Group II (n = 15) received CCK receptor antagonist (L-364,718), 0.1 mg/100 g body wt subcutaneously BID. Group III received CCK receptor antagonist in the same dose but treatment was started after tumors became palpable. All animals were examined daily. Latency for tumor growth, tumor size, and body weight were recorded. Animals were sacrificed after 3 weeks and final tumor volume and weight were measured. CCK receptor antagonist (L-364,718) significantly reduced pancreatic carcinoma growth when given immediately after transplantation and also in animals with established tumor. However, this inhibitory effect of L-364,718 was only partial and effective only for a brief time. This finding suggests CCK may have only a minimal influence on the biologic behavior of exocrine pancreatic cancer.

Is the CCK-8 induced relaxation of the feline sphincter of Oddi mediated by VIP neurons?

The regional, intraarterial, injection of CCK-8 elicits reciprocal effects on the motility of the extrahepatic biliary tree in the cat: the contraction of the gallbladder and a relaxation of the sphincter of Oddi as well as of the duodenal wall. After neural blockade with tetrodotoxin the responses of the sphincter to CCK-8 were blocked, and the responses of the gallbladder were markedly reduced. After the regional administration of a VIP antiserum the sphincter relaxation in response to CCK-8 was blocked. Immunocytochemically it was demonstrated that the feline sphincter contains a rich VIP-ergic innervation, while CCK-like immunoreactivity was found only in mucosal endocrine cells. The results indicate that CCK-8 selectively activates inhibitory VIP neurons innervating the sphincter. After the administration of a nonpeptide CCK-receptor antagonist, the CCK-8 induced motor responses of both the sphincter and the gallbladder were markedly reduced. This indicates that blockade of CCK-8 receptors involves muscular as well as neural CCK-receptors.