Cholecystokinin satiety and orosensory feedback

Cholecystokinin octapeptide (1.5 μg/kg CCK) was effective in reducing the number of bar-press responses for food reward. However, during the extinction session when a food pellet did not follow the bar-press, CCK was not effective in reducing the number of responses. Since the number of bar-presses during extinction is known to be positively related to the duration of food deprivation we concluded that CCK by itself did not reduce the hunger drive or the state of arousal related to food deprivation. The orosensory feedback from food intake was regarded to be a crucial element in the effect of CCK to promote satiety. It might be that food intake was needed to test the new state of satiety induced by CCK and thus without food intake during the extinction session the effect of CCK was not shown. We think that CCK may be characterized as a satiety inducer but probably not a hunger reducer. An attempt to introduce a limited amount of orosensory feedback during the extinction session was not successful in restoring the effect of CCK to suppress the food related operant response probably due to lack of proper temporal relationship between the CCK injection and the limited orosensory stimulation introduced.