The effects of repeated intraperitoneal administration of the GABAB receptor agonist baclofen on body weight in rats maintained on a restricted feeding schedule.

It has previously been shown that chronic systemic administration of the GABAB agonist, baclofen, reduces body weight in free feeding rats but has no effect on long-term food intake. The present study was conducted to extend these observations by investigating the effects of baclofen on body weight, food intake and water consumption in rats maintained on a restricted feeding schedule. The rats were allowed free access to food for 3 hours each day and injected intraperitoneally (i.p) once daily over a period of 11 days with baclofen (4 mg / kg; n=8) or saline (Control Group; n=8) immediately after each feeding session. Baclofen treatment produced small decreases in food intake on Days 2, 4 and 5 (P<0.05) compared with control animals but there were no differences between the 2 groups on Days 6 to 11. Baclofen did not affect prandial water intake. However, baclofen significantly decreased body weight gain of the animals (F(1,14) = 22.0, P < 0.01) starting 3 days after the initiation of treatment. During the subsequent 9 days both groups received no treatments. However, the "Baclofen Group" continued displaying significant reductions in body weight gain (F(1,14) = 8.47 p<0.01) but there were no significant differences in food and water consumption between the 2 groups of animals. The results of this study indicate that repeated administration of baclofen to food-restricted rats for 11 days reduces body weight and that the effects persist when the drug is withdrawn. While it is possible that the decrease in food intake during the early period of the experiment may have been partly responsible for the reduction in body weight in the baclofen-treated animals, the observation that these rats displayed reduction in body weight during the latter part of the study when there was no significant differences in food intake between the 2 groups, suggests that the drug decreases body weight independently of its effects on food consumption.