Integration of vagal afferent responses to duodenal loads and exogenous CCK in rats.

The neurophysiological responses to 0.1 ml duodenal balloon inflation, 0.5 ml duodenal loads of normal saline, and 100 pmol close celiac arterial infusions of cholecystokinin (CCK) were obtained from 14 left cervical vagal afferent fibers in 14 rats. Duodenal, but not gastric, loads increased discharge rates in these slowly adapting fibers. CCK alone excited these fibers, and CCK pretreatment amplified subsequent duodenal load responses. Furthermore, duodenal loads generated greater responses when combined with CCK infusions. The small (< 3 mm) receptive fields of these fibers were localized to the ventral wall of the proximal duodenum, with C fiber conduction velocities (< 2 m/s). These results demonstrate for the first time rat duodenal load-sensitive vagal afferents. They can integrate signals arising from CCK and duodenal loads, and may mediate aspects of the role of CCK in the inhibition of gastric emptying and the control of food intake.