CHOLECYSTOKININ CHANGES THE DURATION BUT NOT THE RATE OF LICKING IN VAGOTOMIZED RATS

Abdominal vagotomy markedly reduces or abolishes the inhibitory effect of cholecystokinin (CCK-8) on meal size. To investigate the rate and microstructure of licking underlying this phenomenon, licking was meas ured throughout a meal of milk in intact and vagotomized rats after in traperitoneal injections of isotonic saline or CCK-8. CCK-8 increased the slope of the decay of licking, decreased the efficiency of licking , and decreased the duration of licking in intact rats but had no effe ct on either the slope of the decay of licking or the efficiency of li cking, but it increased the duration of licking in vagotomized rats. T hese results demonstrate that abdominal vagal nerves are necessary for CCK-8 to increase the rate of decay of licking, but nonvagal mechanis ms mediate the effect of CCK-8 on duration of licking.