Behavioral studies provide in vivo validation for the pivotal role of TLR4 in mediating alcohol action. For example, C3H/HeJ mice have defective TLR4 function and showed decreased alcohol consumption [3]; although there were no changes reported in alcohol intake and preference in TLR4 knockout mice, the learning and memory deficits observed in wild type mice following ethanol treatment were not observed in TLR4 knockout mice [34]. In addition to preventing cognitive impairments, mice lacking TLR4 were protected against alcohol-induced glial activation and anxiety [34]. Genetic deficiency of either TLR4 or MyD88 reduced acute alcohol-induced sedation and motor impairment in mice, suggesting involvement of the TLR4-MyD88 dependent pathway in the acute behavioral actions of alcohol [28*]. Moreover, deficiency of TLR4 prevents LPS-induced sickness behavior and provides resistance to chronic alcohol consumption [35]. When TLR4 is targeted in rat amygdala using small inhibitory RNAs, self-administration of alcohol is reduced [36*], showing that reduction of TLR4 in a single brain region is sufficient to reduce alcohol administration. Furthermore, knockout mice lacking the TLR4 adaptor protein, CD14, drink less alcohol [26] and are resistant
