Effects of intraperitoneal administration of the GABAB receptor agonist baclofen on food intake in rats measured under different feeding conditions

The effects of intraperitoneal (i.p.) administration of the GABAB receptor agonist baclofen were assessed in rats under different feeding conditions. In Experiment 1, it was observed that baclofen (1-4 mg/kg) significantly (at least, P < 0.05) increased cumulative food intake in non-deprived rats during the 120 min measurement period during the early light phase of the light-dark cycle. By contrast, during the early dark phase of the light-dark cycle in non-deprived rats, the 1 mg/kg doses of baclofen significantly increased cumulative feeding at 30, 60 and 120 min (at least P < 0.05), the 2 mg/kg dose significantly increased feeding at 30 and 60 min (at least P < 0.05) and the 4 mg/kg dose had no effects on feeding. In Experiment 2, baclofen (1-4 mg/kg) was found to produce no significant effects on food intake in rats that were food-deprived for 22 h. In Experiment 3, the effects of baclofen were investigated on food intake in 16 h food-deprived rats that had received an oral preload for 2 h prior to drug administration. Baclofen (1-4 mg/kg) significantly increased cumulative food consumption (at least, P < 0.05) only during the first 30 min after administration in these animals. The results of this study indicate that the effects of baclofen on food intake may be related to the state of hunger or satiety of the animals and the time during the light-dark cycle when the drug is administered.