Effect of CCK pretreatment on the CCK sensitivity of rat polymodal gastric vagal afferent in vitro

Abstract

To prevent the blood-borne interference and reflex actions via neighboring organs and the central nervous system, the study was conducted in an in vitro isolated stomach-gastric vagus nerve preparation obtained from overnight-fasted, urethan-anesthetized rats. Afferent unit action potentials were recorded from the gastric branch of the vagus nerve. The left gastric artery was catheterized for intra-arterial injection. In vitro we found that 1) 55/70 gastric vagal afferents (GVAs) were polymodal, responding to CCK-8 and mechanical stimuli, 13 were mechanoreceptive, and 2 were CCK-responsive; 2) sequential or randomized intra-arterial injections of CCK-8 (0.1-200 pmol) dose-dependently increased firing rate and reached the peak rate at 100 pmol; 3) the action was suppressed by CCK-A (Devazepide) but not by CCK-B (L-365,260) receptor antagonist; 4) neither antagonist blocked the mechanosensitivity of GVA fibers. These results are consistent with corresponding in vivo well-documented findings. Histological data indicate that the layered structure of the stomach wall was preserved in vitro for 6-8 h. Based on these results, it seems reasonable to use the in vitro preparation for conducting a study that is usually difficult to be performed in vivo. For instance, because there was no blood supply in vitro, the composition of the interstitial fluid, i.e., the ambient nerve terminals, can be better controlled and influenced by intra-arterial injection of a defined solution. Here we report that acutely changing the ambient CCK level by a conditioning stimulus (a preceding intra-arterial injection of increasing doses of CCK-8) reduced the CCK sensitivity of GVA terminals to a subsequent test stimulus (a constant dose of CCK-8 intra-arterial injection).

A novel preparation to study rat pancreatic spinal and vagal mechanosensitive afferents in vitro

“…The mechanical sensitivity of vagal afferents in the wall of the upper gastrointestinal tract is well documented and classified 1 . In this study, mechanical receptive fields in these organs were commonly identified by manual probing and were generally equivalent to afferent responses previously described in both in vivo and in vitro preparations 20–23 . In the studies reported here, mechanical responses in areas of the gut wall and those associated with blood vessels were readily identifiable by manual probing, however, in the same preparation, there was a complete absence of response from the pancreas and its internal vasculature suggesting a difference in the vagal properties and/or innervation of this organ.…”

Cholecystokinin and Gastrin Receptors

“…Gastric CCK-responsive vagal afferent fibers have been identified on in vitro isolated stomach-vagus nerve preparations (564). A population of CCK1R-immunoreactive fibers, localized in the gastric mucosa, markedly decreased following subdiaphragmatic vagotomy, suggesting a vagal origin (501).…”

The sensitization of peripheral C-fibers to lysophosphatidic acid in bone cancer pain

“…The organ bath used was the same as described in our previous study (Wei and Wang 2000). Rats were anesthetized with urethane (1.5 g/kg).…”