Effects of dexfenfluramine on glucose drinking and glucose-conditioned flavour preferences in rats: taste versus post-ingestive conditioning.

A comparison was made of the effects of dexfenfluramine (DF, 3-10 mg kg-1) on intake of and conditioning with glucose solutions varying in orostimulant properties (taste) and post-ingestive actions (calories), in rats. First, sham-feeding, using gastric-fistulated rats, was performed to assess the orostimulant properties of the solutions. Then, two experiments were done. In the first experiment, we examined the effects of DF, given at doses of 13 and 10 mg kg-1, on the intake of two glucose solutions having different orostimulant properties and different caloric values. The solutions were a mix of 1% glucose plus 0.125% saccharin (low caloric, more orostimulant), and 4% glucose (high caloric, less orostimulant). At doses of 10 mg kg-1, DF administration markedly reduced intake of both solutions (P < 0.05 vs Control Group, respectively). In second experiment, we examined the effects of DF (10 mg kg-1) on flavour preference conditioning in two parts. In the first part of the experiment, rats consumed two distinctively flavoured solutions having equal orostimulant properties but different caloric value for a conditioning period of 16 days. The solutions were a mix of 1% glucose plus 0.125% saccharin (low caloric), and 6.1% glucose (high caloric). At the end of the conditioning period, the flavour paired with ingestion of more calories was subsequently preferred (P < 0.05 vs low caloric glucose-saccharin mix). DF, when given during and after the conditioning period, attenuated this flavour-calorie conditioning (P < 0.05 vs Control Group). In the second part of the experiment, rats were conditioned with flavours associated with a mix of 20% glucose plus 0.4% citric acid and 20% glucose solutions. These solutions were equally caloric but differed in orostimulant properties. The flavour paired with better orostimulant properties was subsequently preferred (P < 0.05 vs less orostimulant glucose-citric acid mix). DF, when given during and after the conditioning period, also attenuated this flavour-flavour conditioning (P < 0.05 vs Control Group). These results suggest that DF may impair flavour preference learning.