VAGAL AFFERENT AND EFFERENT CONTRIBUTIONS TO THE INHIBITION OF FOOD-INTAKE BY CHOLECYSTOKININ

To assess the role of subdiaphragmatic vagal afferent and efferent fib ers in the mediation of the inhibition of food intake by cholecystokin in (CCK), we compared the ability of a dose range (1-16 mu g/kg) of CC K to affect 30-min liquid glucose (0.125 g/ml) intake in rats with eit her total subdiaphragmatic vagotomy, selective subdiaphragmatic vagal deafferentation, selective subdiaphragmatic vagal deefferentation, or sham surgery. Selective vagal deafferentation and deefferentations wer e produced by combinations of unilateral subdiaphragmatic vagotomy and contralateral afferent or efferent rootlet transection as fibers ente r the caudal medulla. CCK produced a dose-related suppression of gluco se intake in sham animals, and this action was eliminated in rats with total subdiaphragmatic vagotomy CCK suppression of intake was attenua ted in rats with vagal deafferentation, such that there was a loss of sensitivity to CCK. Vagal deefferentation resulted in lower levels of baseline intake and a truncation of the feeding-inhibitory actions of CCK. These data demonstrate that CCK's suppression of intake depends o n actions of both vagal afferent and efferent fibers. We interpret the se data as suggesting that 1) the actions of low doses of CCK depend o n activation of vagal afferent CCK receptors and 2) the greater effica cy of higher CCK doses is the result of the potentiation of these vaga l afferent actions due to local physiological gastrointestinal effects of the peptide that rely on vagal efferent input.