Fig. 3.

Loss of neural AP-3 preferentially impairs the response of VMAT2⁺ synaptic. vesicles to high-frequency stimulation. Midbrain dopamine neurons expressing VMAT2-pH were stimulated in the presence of 100 nM bafilomycin with 1,000 action potentials at 35 °C (A and C). Dopamine neurons expressing VGLUT2-pH were stimulated without bafilomycin for 20 s at 35 °C (B). The fluorescence intensity was normalized to that in NH₄Cl. (A) Cultures from WT and β3B KO mice were stimulated at different frequencies and the mean initial slope and pool size are shown below (n = 9 to 10 coverslips for WT for β3B KO from three different cultures). (B) Cultures from WT and β3B KO mice were stimulated at different frequencies and the mean initial slope and peak are shown below (n = 9 coverslips from two different cultures). (C) Cultures from WT and Vps41 cKO mice were stimulated at 5 and 25 Hz, the mean pool size and initial slope are shown to the right (n = 9 to 10 coverslips for WT and Vps41 cKO from three different cultures). ***P < 0.001; ****P < 0.0001; ns, nonsignificant by two-way ANOVA with Sidak’s multiple comparisons test. Error bars indicate SEM.