Obesity affects about 42% of adults in the United States. Most states report obesity in 30% of adults (the State of Obesity 2022: Better Policies for a Healthier America), with health-related costs estimated around $150 billion (Zamosky, 2013). As multimodal therapies are most effective in reducing obesity’s effects, this study seeks to determine if cholecystokinin (CCK), a hormone released upon food consumption that reduces meal size and duration, affects the discriminative stimulus effects of 22-hrs food deprivation. Sprague-Dawley rats (24 females, 24 males) were trained to press the left lever after 22-hr food deprivation. Fifteen responses earned a 45 mg food pellet, and 15 right lever presses resulted in 8 seconds of darkness. Contingencies reversed under 2-hr food deprivation. After acquiring discrimination (males: M=76, SEM 7, females: M=83, SEM 7 sessions to criteria), subjects were injected with saline (1 ml/kg body weight) or CCK (1 to 10 mg/kg, i.p.) 15 minutes before a 5-minute test session. Food intake was then measured. CCK did not alter "hunger"-like responses nor affect lever pressing rates or food intake. In food tests under 22-hr deprivation, male rats ate more grams of food, while female rats ate similarly in both deprivation conditions.
