circuit. Therefore, to determine if DPM activation has an inhibitory effect on MBs, we used P2X2 receptors
to activate the DPMs and expressed the fluorescent intracellular chloride sensor SuperClomeleon
(Grimley et al., 2013) in the MBs. We found that DPM activation evoked an increase in chloride in the
MBs which could be almost completely blocked by bath-application of picrotoxin (Figure 5A). To
determine if these results could be caused by DPM GABA release, we bath-applied GABA and
observed similar MB SuperClomeleon responses in the presence of TTX, which could be completely
blocked by picrotoxin (Figure 5B). These results demonstrate that DPM neurons inhibit the MBs via
activation of GABAA receptors.