DUODENAL NUTRIENT EXPOSURE ELICITS NUTRIENT-SPECIFIC GUT MOTILITY ANDVAGAL EFFERENT SIGNALS IN RAT

Volume and chemical characteristics of meals in the gut have been prop osed to generate vagal afferent signals that mediate the negative feed back control of ingestion and gastric emptying. Furthermore, duodenal nutrients elicit changes in gastrointestinal motility that may stimula te mechanosensitive vagal afferents. The degree to which the activity of an individual vagal afferent fiber can be modified by both mechanic al and nutrient properties in the gut remains unclear. The present stu dies evaluated the relationships between distal antral and proximal du odenal load-sensitive vagal afferent activity and gastroduodenal motil ity in response to duodenal nutrient exposure in ketamine-xylazine-ane sthetized rats. Duodenal carbohydrate (glucose) and amino acid (pepton e) infusions (0.2 ml/min, 0.2-0.5 kcal/ml) stimulated concentration-de pendent increases in 1) antroduodenal contractions and 2) antral and d uodenal vagal afferent activity beyond those attributable to osmolarit y alone. In addition, duodenal peptone was more effective than equical oric glucose in eliciting this vagal activity. These data demonstrate that the proximal duodenum can discriminate its nutrient chemical cont ents and that gastroduodenal load-sensitive vagal afferents indirectly transduce nutrient chemical information.