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Figure 7
(A) Schematic of whole-cell recording of downstream neuronal targets of vsx1:Gal4;UAS:CoChR2-tdTomato+ neurons using optical stimulation. (B) Example voltage-clamp traces from a target neuron held at Vhold –80 mV or 0 mV during optical stimulation of the upstream sister neuron pair. Optical stimulation evoked excitatory postsynaptic currents (EPSCs) onto the target neuron (top) but not inhibitory postsynaptic currents (IPSCs) (middle), indicating connectivity from the V2a but not the V2b. Bottom: application of glutamatergic antagonists blocks the evoked EPSCs. (C) As in (B) for another target neuron, this one showing evoked IPSCs but not EPSCs. IPSCs were abolished by application of strychnine (bottom). (D) Example voltage-clamp traces from a target neuron held at Vhold –80 mV or 0 mV. Trace showing a small, slow evoked EPSCs without any fast component. These are presumably due to indirect (polysynaptic) electrical connectivity from the optogenetically activated V2a neuron. (E) Mean evoked amplitude of optogenetically evoked EPSCs and IPSCs in each target neuron. 12/14 synaptically connected targets received only EPSCs or IPSCs, while 2/14 neurons received both EPSCs and IPSCs. (F) Bar graph depicting the number of EPSC only (n = 6), IPSC only (n = 6), both EPSC/IPSC (n = 2), and no responses (n = 75) (black) or only slow presumed polysynaptic (gray) (n = 10) detected across all target neurons recorded. (G) Scatterplot showing the distinction between mean evoked amplitude and 20–80% rise time for fast and slow evoked EPSC responses. (H) Schematic depicting the two presumed types of vsx1 GFP+ sister pairs observed. (I) Summary of circuit integration pattern observed among sister V2a/b pairs. Source data for this figure are given in Figure 7—source data 1.
Sister V2a/b neurons provide asymmetric input onto downstream neurons in spinal cord.