To test whether the hydrophobic pocket in GIRK2 is the site for alcohol-mediated activation, we first investigated whether GIRK2 channels are sensitive to MPD modulation. Whereas primary alcohols up to the size of butanol (1-BuOH; four carbons) activate GIRK1/2 channels7,8, the effect of MPD with five backbone carbons was unknown. GIRK2 channels expressed in HEK-293T cells produced a small inwardly rectifying basal K+ current that was inhibited by extracellular Ba++ (Fig. 1e). Bath application of MPD (100 mM) increased the amplitude of the inwardly rectifying current (Fig. 1e), indicating that MPD activates GIRK channels. Note also that MPD appeared to inhibit an endogenous voltage-gated outward current at positive potentials (Fig. 1e, arrow), which is likely a voltage-gated K channel9. All three alcohols activated GIRK2 channels at 10 mM and displayed a steep increase in activation around 100 mM (Fig. 2a). The activation curve for MPD falls between EtOH and 1-PrOH (Fig. 2b) and does not reach a maximum, similar to previous studies7,8. These results show that MPD activates GIRK2 in a similar manner to other small n-alcohols. Interestingly, 1-pentanol (1-PeOH),
