Effect of dexfenfluramine on body weight set-point: study in the rat with hoarding behaviour

The food hoarding behaviour paradigm (HB) was used to evaluate the modification of the set-point of body weight (BW) regulation induced by dexfenfluramine (D-FF) in rats fed with chow or previously made obese by a cafeteria diet for 51 days. Daily injections of D-FF at a dose of 7 mg/kg (i.p.) induced a 58.5 g shift-down of the BW set-point in a group of chow fed rats submitted to HB measurement, and induced an equivalent weight reducing effect in a control-BW group always fed with chow ad libitum. In the rats fed ad libitum with the cafeteria diet, the BW reducing effect of D-FF(7 mg/kg/day) was about twice as great as in the lean rats. The HB measurement indicates that the vehicle-injected/cafeteria-obese rats had a BW set-point 54.6 g lower than the BW they reached when fed ad libitum with the cafeteria diet. It was concluded that the hyperphagia induced by the cafeteria diet was above that needed for BW regulation, and that D-FF may suppress this unregulated weight increase. In the cafeteria-obese rats submitted to HB measurement and D-FF injections a BW set-point 110.7 g lower than their initial ad libitum BW was observed. It is concluded that D-FF has induced a double effect in these rats: (1) a shift-down of the BW set-point and (2) the suppression of the unregulated weight increase induced by the cafeteria diet.