Reducing effect of a Phaseolus vulgaris dry extract on operant self-administration of a chocolate-flavoured beverage in rats

Extracts from or derivatives of Phaseolus vulgaris beans reduce body weight and food intake, including highly palatable foods and fluids, in multiple rodent models of overeating and obesity. The present study was designed to assess whether a standardised P. vulgaris dry extract was effective in reducing also the operant self-administration of a chocolate-flavoured beverage. To this end, rats were initially trained to lever-press for a chocolate-flavoured beverage under a fixed ratio 10 schedule of reinforcement in daily 60 min sessions. Once lever-responding reached stable levels, the effect of a P. vulgaris dry extract on the number of lever-responses for the chocolate-flavoured beverage was determined. Pretreatment with 50, 200 and 500 mg (intragastric) P. vulgaris dry extract per kg produced an approximate 15, 35 and 40 % reduction, respectively, in lever-responding for the chocolate-flavoured beverage. These results indicate the capacity of a P. vulgaris preparation to reduce the reinforcing properties of a highly palatable fluid in rats.