Slowing of intestinal transit by PYY depends on an adrenergic pathway

Abstract

BACKGROUND: Intestinal transit is slowed by peptide YY (PYY) (Gut 28:166,1987). Although reflex inhibition of intestinal motility is known to depend on an adrenergic efferent pathway from the prevertebral ganglia (J Neurophysiol 7:163,1944), it is unknown whether the slowing of intestinal transit by PYY also involves this pathway. To test the hypothesis that the slowing of intestinal transit by PYY depends on an adrenergic pathway, we compared intestinal transit during buffer perfusion of the proximal and distal gut in the absence and presence of the beta-adrenergic blocker, propranolol. METHODS: Four dogs were equipped with duodenal (10 cm from the pylorus) and midgut (160 cm from the pylorus) fistulas. Using occluding Foley catheters, the small intestine was compartmentalized into the proximal (between fistulas) and distal (beyond midgut fistula) one-half of gut. Buffer (pH 7.0) was perfused into both the proximal and distal gut at 2 ml/min for 90 min. PYY was delivered intravenously at 0.8 pg/ kg/h over 90 min, while 50 pg/kg/h propranolol (Prop) or 0.15 M NaCI was delivered intravenously. Intestinal transit across the proximal gut (mean _+ SE) was measured by the recovery of 99m-Tc-DTPA in the output of the midgnt fistula during the last 30 rain of the 90 min experiment. The cumulative % marker (mean -+ SE) recovered was compared using 1-way ANOVA with additional analysis by paired t-tast. RESULTS: 1.Intestinal transit depended on test conditions (p < 0.0005). 2.Intestinal transit was slowed by PYY so that marker recovery was reduced from 74.9 _+ 4.4% (control)to 15.3 _+ 6.3% (PYY)(p < 0.0005). 3.Tho slowing of intestinal transit by PYY was reversed by propranolol, so that marker recovery increased from 15.3 _+ 6.3% (PYY) to 72.2 + 4.8% (PYY + Prop) (p < 0.005). CONCLUSION: The slowing of intestinal transit by PYY depends on a propranolol-sensitive, adranergic pathway.