Involvement of apolipoprotein A-IV and cholecystokinin₁ receptors in exogenous peptide YY_3-36-induced stimulation of intestinal feedback

Peptide YY (PYY)_3-36, released by intestinal lipid elicits functional effects that comprise the intestinal feedback response to luminal nutrients, but the pathway of action is not fully characterized. The aim of the present study was to determine the role of the apolipoprotein (apo) A-IV-cholecystokinin (CCK)₁ receptor (CCK₁R) pathway in exogenous PYY_3-36-induced activation of the gut-brain axis and inhibition of gastric emptying and food intake. PYY_3-36 (5 μg/100 g ip) significantly inhibited gastric emptying of a chow meal in wild-type but not A-IV^-/- mice andCCK₁R receptor blockade with devazepide (10 μg/100 g), abolished PYY_3-36-induced inhibition of gastric emptying. PYY_3-36-induced inhibition of food intake in both ad libitum-fed and 16-h fasted mice was unaltered in A-IV^-/- mice, compared with wild-type controls, or by CCK₁R receptor blockade with devazepide. PYY_3-36 activated neurons in the midregion of the nucleus of the solitary tract (bregma -7.32 to -7.76 mm) in A-IV^+/+ mice; this was measured by immunohistochemical localization of Fos protein. PYY _3-36-induced Fos expression was significantly reduced by 65% in A-IV^+/+ mice pretreated systemically with the sensory neurotoxin capsaicin (5 mg/100 g), 78% by the CCK₁R antagonist, devazepide (10 μg/100 g), and 39% by the Y2R antagonist, BIIE0246 (200 and 600 μg/100 g) and decreased by 67% in apo A-IV^-/- mice, compared with A-IV ^+/+ controls. The data suggest a role for apo A-IV and the CCK ₁Rin PYY_3-36-induced activation of the vagal afferent pathway and inhibition of gastric emptying, but this is likely not the pathway mediating the effects of PYY_3-36 on food intake.