Effects of intraperitoneal administration of the GABAB receptor agonist baclofen on food intake in CFLP mice

Ivor S. Ebenezer & Monika Prabhaker. Neuropharmacology Research Group, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, PO1 2DT, U.K.

We have shown that systemic administration of the GABAB receptor agonist baclofen increases food intake in non-deprived rats (Ebenezer et al., 1992) by a central mode of action (Ebenezer et al., 2004), and we have also provided evidence that endogenous central GABA, acting at central GABAB receptors, plays a physiological role in the regulation of food intake (Patel et al., 2004). More recently, it has been shown that baclofen increases food intake in non-deprived C57BC6 mice (Ebenezer, 2005). It has been reported that, in some cases, different strains of mice respond differently to the effects of pharmacological agent on food consumption (see Lewis et al., 2006). The present study was therefore undertaken to investigate the effects of baclofen on food intake in CFLP mice to determine if the GABA B receptor agonist has similar effects in another strain of mice.

Male CFLP mice (body weight: 45 - 55 g, n = 14) were divided into two equal groups. During the experimental trials, the mice in the Control Group were injected i.p. with physiological saline and those in the Treatment Group with baclofen (1 - 8 mg kg-1). Food was presented 5 min after injection. The amount of food consumed was measured at 120 min. The mice in the Treatment Group received all doses of baclofen while the mice in the Control Group received saline injections during each trial. Seven days separated successive trials. The data was analysed by two-factor ANOVA with repeated measures on treatment and post-hoc Dunnett’s test. The results are illustrated in Fig. 1 and show that baclofen caused a dose-dependent increase in food intake. Analysis of the data showed significant main effects of group (F(1,14)=7.103, P<0.05) and treatment (F(2,28)=5.683, P<0.01). Post-hoc tests revealed that the 4 and 8 mg kg-1 dose of baclofen significantly increased cumulative food intake in the animals. The 1 mg kg-1 dose was without significant effect. The present results extend previous observations in C57BC6 mice and indicate that systemic administration of baclofen causes increases in food intake in a different strain of mouse. As the mouse can be genetically manipulated, the present results suggest the possibility of using such molecular techniques to further investigate the role of GABA and GABAB receptors in the regulation of feeding.

Fig. 1. Effects of Baclofen (1-8 mg kg ) on food intake in non-deprived CFLP mice.Vertical lines rep. s.e. mean.**P<0.01

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