Benzodiazepine-induced hyperphagia: a test of the hunger-mimetic model

The 'hunger-mimetic' model is a prominent explanatory account of benzodiazepine-induced hyperphagia. A salient feature of food deprivation (hunger) in laboratory animals is 'finicky' eating, or an enhanced reactivity to the palatability of food. If the hunger-mimetic model is correct, a similar finicky pattern of increased eating should be observed both in hungry (food-deprived) rats and in benzodiazepine-treated, hyperphagic rats. Two groups of rats were matched on measures of ad lib baseline intake of both a highly palatable food (sweetened condensed milk) and a food low in palatability (milk adulterated with 37.5 mg% quinine). Subsequently one group was placed on a moderate food deprivation schedule while the second group was maintained on ad lib food but was injected (IP) with 5 mg/kg chlordiazepoxide (CDP) 30 min prior to food presentation tests. Single-bottle tests indicated that while the food deprived animals exhibited a greater augmentation of eating when given the high-palatability food, the animals pretreated with CDP exhibited an indiscriminate elevation of eating across both foods. Similarly, on two-bottle choice tests the food-deprived rats exhibited an enhanced preference for the high-palatability food, whereas the CDP-treated animals did not change from baseline food preference. These results fail to support the hunger-mimetic model of benzodiazepine-induced hyperphagia. Alternative models based on a perseverative, disinhibitory action of benzodiazepines are discussed.