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We have shown that non-sulfated cholecystokinin-8 (NS CCK-8) reduces food intake in adult male Sprague Dawley rats by activating cholecystokinin-B receptor (CCK-BR). Here, we tested the hypothesis that the vagus nerve and the celiaco-mesenteric ganglia may play a role in this reduction. The hypothesis stems from the following facts. The vagus and the celiaco-mesenteric ganglia contain NS CCK-8, they express and have binding sites for CCK-BR, NS CCK-8 activates CCK-BR on afferent vagal and sympathetic fibers and the two structures link the gastrointestinal tract to central feeding nuclei in the brain, which also contain the peptide and CCK-BR. To test this hypothesis, three groups of free-feeding rats, vagotomy (VGX), celiaco-mesenteric ganglionectomy (CMGX) and sham-operated, received NS CCK-8 (0, 0.5 and 1 nmol/kg) intraperitoneally prior to the onset of the dark cycle and various feeding behaviors were recorded. We found that in sham-operated rats both doses of NS CCK-8 reduced meal size (MS), prolonged the intermeal interval (IMI, time between first and second meal), increased satiety ratio (SR = IMI/MS), reduced 24-h food intake and reduced the number of meals relative to saline control. In the VGX and the CMGX groups, all of the previous responses were attenuated. Consistent with our hypothesis, the findings of the current work suggest a role for the vagus nerve and the celiaco-mesenteric ganglia in the feeding responses evoked by NS CCK-8.

Recently, we reported that non-sulfated cholecystokinin-8 (NS CCK-8) reduces food intake by cholecystokinin-B receptors (CCK-BR). To examine a possible site of action for this peptide, and based on the fact that both NS CCK-8 and CCK-BR are found centrally and peripherally, in the current study we hypothesized that NS CCK-8 increases Fos-like immunoreactivity (Fos-LI, a neuronal activation marker) in the dorsal vagal complex (DVC) of the hindbrain and the myenteric and submucosal plexuses of the small intestine. We found that intraperitoneal NS CCK-8 (0.5 nmol/kg) increases Fos-LI in the DVC, the myenteric and the submucosal plexuses of the duodenum and the myenteric plexus of the jejunum. The findings suggest, but does not prove, a potential role for the DVC and the enteric neurons in the feeding responses evoked by NS CCK-8., (Copyright © 2018 Elsevier B.V. All rights reserved.)