LPS treatment alters some behaviors, which potentially may modify the alcohol consumption. Acutely, LPS decreases preference for saccharin, increases intake of quinine and reduces fluid intake (Aubert and Dantzer, 2005). However, it does not change sucrose palatability (Cross-Mellor et al., 1999). Cross-Mellor et al. (2009) showed that LPS-induced immune system activation significantly impairs the rapid acquisition of a conditioned taste aversion to LiCl–sucrose mixture in taste reactivity tests. In contrast, Larson (2006), using a CPP procedure, showed that LPS and IL-1β decreased sucrose intake (sucrose used as a primary reinforcer) but had no effect on the expression of a sucrose-induced place preference (sucrose-paired environment as a conditioned reinforcer), indicating a differential effect of immune system activation on appetitive behaviors maintained by primary and conditioned reinforcers (Larson, 2006). It is important to note that all of these studies explored the immediate effect of LPS injection and are thus studies of the acute “sickness” behavior. In contrast, in all of our experiments mice were allowed to recover from these effects of LPS injection before testing.
