Photoinactivation of the a1-I subunit of V0 impairs synaptic transmission. (A) Representation of the V0 a1-I subunit with the Flag (blue) and TC tags in the N- or C-terminal position. (B) Micrograph illustrating the experimental configuration with a patch-clamped presynaptic GFP-expressing neuron (stimulated neuron, colorized in green) and a connected untransfected neuron (voltage clamped to measure the postsynaptic response). Bar, 20 µm. (C) Evolution of the postsynaptic current amplitude in response to presynaptic action potentials (stimulation every 30 s) of rat hippocampal neurons expressing GFP alone (open circles) or GFP + V0 TC-tagged a1-I subunit (filled circles). Current amplitudes were expressed in the percentage of their mean amplitude before the photoinactivating flash. Neurons were successively incubated with 1 µM FlAsH-EDT₂ for 10 min and 1 mM BAL without modification of the postsynaptic responses. Photoinactivation was carried for 1 min (gray area). Data shown are from single representative experiments out of three (open circles) or four (filled circles). Typical presynaptic action potentials (Pre) and postsynaptic responses (Post) either before (1) or after (2) the flash are shown. Dotted lines correspond to the mean amplitude of the postsynaptic responses before (top line) or after the photoinactivating flash (bottom line). (D) Averaged effects of V0 a1-I subunit photoinactivation on synaptic transmission. Pooled results include six neuronal pairs, either GABAergic or glutamatergic (paired Student’s t test).