Figure 3: Parkin mutants display depolarisation of the muscle resting membrane potential coupled with reduced EJP amplitudes. (a) Spontaneous excitatory junction potentials (EJPs) were recorded from muscle 6 or 7. The mean resting potential and amplitude of the EJPs in the parkin mutant (parkZ3678/parkin25) were ~12 mV more positive than in wild-type (CS/w1118). In this recording both the Is and Ib EJPs are visible: both were reduced in the parkin mutant. (b) The spontaneous miniature EJPs (mEJPs) are smaller in the parkin mutant, as shown by these two recordings made at the same RMP. (c) Quantification of the change in resting membrane potential (RMP) in the parkin mutant, and the rescue by expression of Drosophila wild-type parkin in the muscle (G14 GAL4), but not the nerve (elav3e1 GAL4). (d) The plot of the size of Is EJP as a function of RMP shows that the more negative the RMP, the larger the EJP. However, at any chosen RMP, the wild-type EJP is bigger than those recorded from the parkin mutant. Note that all the green data points lie above the red regression line plotted through the parkin data. Expressing parkin in the nerves leads to data points that significantly lie above the red regression line, , , showing effective rescue of the phenotype. parkin expression in the muscle leads to data distributed symmetrically about the regression line, no rescue. Data from [23] with (d) showing some data reanalyzed.