The effects of the GABAB receptor agonist baclofen on the consumption of normal chow and palatable food in fasted rats

We have previously demonstrated that the GABAB receptor agonist baclofen increases acute food intake in a number of animal species (1).The aim of the present study was to investigate the effect of baclofen on the consumption of normal and palatable foods in hungry rats when simultaneously presented.Male Wistar rats (n=16, body weight: 278 – 323g) were fasted for 18 h each day and allowed 6 h access to their normal rat chow, palatable food (shortbread), and tap water in individual experimental cages. Following an acclimatisation period, during which baseline consumption was measured, the rats were given daily ip injections of either baclofen (8 mg/kg; n=8 rats) or saline (n=8 rats) and placed in the experimental cages immediately after injection for 6 h each day for 14 days. Consumption of normal and palatable food was measured at the end of each session, as described previously (1). During days 15 to 19, all the animals were given saline injections; during days 20 to 23, the rats were injected with either saline or baclofen, according to their original groupings. The food intake data were analysed by ANOVA with repeated measures on days and the post-hoc Tukey test.The results are shown in Figure 1. Both groups of animals consumed more of the palatable food compared with their normal chow during the acclimatisation period. Day 0 in Figure 1A and B shows the baseline food consumption during the last acclimatisation trial. Rats injected daily with physiological saline continued to display a preference for the palatable food over their normal chow. By contrast, rats that were injected with baclofen exhibited a reversed preference; they consumed significantly (P<0.01) more of their normal chow and significantly (P<0.01) reduced their intake of the palatable food over the 14 day measurement period. However, when these animals were injected with saline during days 15 to 19, they reverted to a preference for the palatable food. This was significantly (P<0.01) reversed again when the baclofen injections were reinstated during days 20 to 23 (see Figure 1 A and B).The results of this study indicate that baclofen produces a reduction in the preference for palatable food but increases the preference for normal rat chow. This phenomenon can be readily reversed by withdrawal of the drug, and reinstated by reintroducing the drug. These finding suggest that a GABAB receptor mediated mechanism may play a role in the control of food preference. Figure 1. Effects of saline and baclofen on consumption of (A) normal rat chow, and (B) palatable chow.
(1) Ebenezer IS (2012). Eur J Pharmacol 690: 115-118