A Phaseolus vulgaris Extract Reduces Cue-Induced Reinstatement of Chocolate Seeking in Rats

Irene Lorrai, Valentina Piga, Mauro A. M. Carai, Antonella Riva, Paolo Morazzoni, Gian Luigi Gessa, Giancarlo Colombo, Paola Maccioni

Previous evidence has suggested that treatment with a standardized dry extract of Phaseolus vulgaris reduced intake and operant self-administration of highly palatable foods and fluids in rats and mice. The present study was designed to assess whether such extract was also effective in reducing seeking behavior for a highly hedonic chocolate-flavored beverage, using a "reinstatement" procedure adopted from the drug addiction research field and modeling relapse behavior. Rats were initially trained to lever-respond for the chocolate-flavored beverage under the Fixed Ratio (FR) 10 schedule of reinforcement. Subsequently, rats were exposed to an extinction responding phase, during which lever-responding - being unreinforced - diminished progressively up to extinction. Lever-responding was then powerfully reinstated by the non-contingent presentation of a complex of gustatory, olfactory, auditory, and visual stimuli previously associated to the availability of the chocolate-flavored beverage. Acute, intragastric administration of P. vulgaris dry extract (100 and 500 mg/kg) reduced lever-responding by 40-45%, in comparison to vehicle condition. These results indicate the ability of P. vulgaris dry extract to reduce seeking behavior for a highly palatable nourishment in an experimental model of relapse into disordered eating of palatable foods. The unavailability of the chocolate-flavored beverage in the reinstatement session tends to exclude that the observed effect of the P. vulgaris dry extract was secondary to any inhibition of carbohydrate metabolism; conversely, it is the likely consequence on a central action on the rewarding and hedonic properties of food.