The sodium channel loop Na_vII-III targets ChR2 to the AIS.

A) Example images (left) of neurons expressing ChR2-YFP-Na_vII-III (top, note background fluorescence revealing the soma of a non-transfected neuron in the YFP channel, with this cell's AIS also clear in the βIV-spectrin channel), or ChR2-YFP (bottom), co-stained for βIV-spectrin. Scalebar, 25 µm. Plots (right) show normalised YFP and βIV-spectrin fluorescence along the axon, with associated AIS localisation indices. Grey box shows AIS location. B, C) Mean correlation r (B) between YFP and βIV-spectrin fluorescence, and mean AISi (C; see text) showing AIS localisation of ChR2-YFP-Na_vII-III. Numbers in bars show n for each group; error bars show SEM; p values report results of t-tests.