Electrophysiology has enabled detailed views of the biophysics of membrane proteins, such as voltage gated ion channels or neurotransmitter receptors (Hille, 2001). Even the functions of many transporters and pumps have been clarified due to their electrogenic or ohmic properties (Fahlke et al., 2016). In some cases, electrophysiological methods have been skillfully applied to ion channels in intracellular membranes, such as mitochondria or lysosomes (Dong et al., 2008; Keller and Hedrich, 1992). What have remained resistant to this approach are the proteins associated with synaptic vesicles, in particular the vesicular neurotransmitter transporters.