Effects of chronic systemic administration of the GABAB receptor agonist baclofen on food intake and body weight in rats

The effects of daily administration of physiological saline of baclofen (1 and 4 mg/kg, i.p.) for 27 days were investigated on food intake and body weight in non-deprived rats in Experiment 1. Baclofen (1 and 4 mg/kg) significantly increased daily short-term food intake when measured at 30 min (F(2,15) = 11.011, P < 0.01) and 90 min (F(2,15) = 7.3801, P < 0.01) over the 27 day experimental period.. Tolerance did not develop to the short-term hyperphagic effects of baclofen. Baclofen (1 mg/kg) had no significant effects on body weight gain of the rats compared with controls. By contrast, baclofen (4 mg/kg) significantly (P < 0.05) decreased the body weight gain of the animals. In Experiment 2, the effect of daily administration of baclofen (4 mg/kg, i.p.) for 24 days was investigated on 24 h food intake in rats measured after the first, eight, fifteenth and twenty second injections. The 24 h food intake of the animals was not significantly different from those of control rats on any of the measurement days (F(1,14) = 1.602, ns). However, the body weight gain of the rats chronically treated with baclofen (4 mg/kg) was significantly reduced. (F(1,14) = 14.011, P < 0.01). The observations that chronic administration of baclofen (4 mg/kg) stimulates short-term food intake without affecting long term (24 h) feeding, but decreases body weight gain, suggest that baclofen may act through different mechanisms to influence food intake and body weight.