Eag1 voltage-gated potassium channels enter and leave synapses by lateral diffusion.
(A) Left, histogram showing the changes of Di values over time for Eag1 channels in hippocampal neuronal cultures. Right, consecutive frames of a representative recording showing diffusion of Eag1 channels inside a presynaptic terminal (Panel 1) and between different presynaptic terminals (Panel 2 and 3; scale bar: 1µm). (B) Di values were fitted to MSD plots generated from either extrasynaptic or synaptic trajectories composed of at least 10 consecutive frames. After binning with a step size of 0.025 µm2/s the number of trajectories was plotted over Di values. Insets, examples of synaptic and extrasynaptic trajectories (scale bar: 200 nm). (C) Median diffusion (±25–75% interquartile range) values for Eag1 channels in extrasynaptic and synaptic trajectories based on data from (B). (D) MSD plots versus time for Eag1 channels inside a synapse (upper graph, consecutive panels from a1 to a3) and outside a synapse (lower graph, consecutive panels from a4 to a6; scale bar: 1µm).