Although the specific mechanisms whereby GABAAR α4 subunit knockdown in the NAc shell decreased responding for ethanol remains to be delineated, knockdown did not affect instrumental responding for the natural reward, sucrose. These results are consistent with our previous findings in which reducing the expression of GABAAR α4 subunit did not influence sucrose intake or preference in the home cage (Rewal et al. 2009). This further strengthens the hypothesis that α4 subunit-containing receptors within the NAc shell specifically mediate the reinforcing effects of ethanol, and not preferred substances in general. A decrease in the responding for ethanol and not sucrose also suggests that sweet taste, at least, is not altered by reducing the expression of GABAAR α4 subunit.
