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. 2019 Jul 3;103(1):102–117.e5. doi: 10.1016/j.neuron.2019.04.022

Figure 2.

Figure 2

Synaptic Transmission between GRP and GRPR Neurons

(A) Bright field (top) and epifluorescence (bottom) images of ChR2-eYFP- and Grpr-eGFP-positive neurons in a transverse lumbar spinal cord slice of a Grp-ChR2;Grpr::eGFP mouse. Scale bar, 5 μm.

(B) Left: experimental setup. Middle: light-evoked photocurrent (473 nm, 1 s) recorded from an initial burst firing Grp-ChR2 neuron (yellow). Right: single blue light pulse-evoked (473 nm, 4 ms) action potential.

(C) Left: experimental setup. Middle: light-evoked EPSCs before (black) and after 1 μM TTX application (magenta) recorded from a Grpr-eGFP neuron. Right: same as left but before (black) and after 20 μM NBQX (purple). Traces are averages of five consecutive responses.

(D) Left: superposition of twenty consecutive light-evoked action potential traces (gray) recorded from a Grp-ChR2 neuron, average response (black). Light stimulation: 473 nm, 4 ms, 0.1 Hz. Right: latency and jitter of light-evoked action potentials recorded from Grp-ChR2 neurons (n = 9, from 7 animals).

(E) Left: twenty consecutive EPSCs traces recorded from a Grpr-eGFP neuron. Right: failure rate, synaptic latency, and jitter of light-evoked EPSCs recorded from GRPR neurons (n = 23 cells from 14 animals).

(F) Left: sagittal lumbar spinal cord section prepared from a Grp-tdTom;Grpr::eGFP mouse immunostained for tdTomato, eGFP, and vGluT2. Arrowheads indicate two examples of vGluT2-positive Grp-tdTom synaptic terminals contacting a Grpr-eGFP neuron dendrite. Right: single focal planes with the corresponding XZ (bottom) and YZ (right) orthogonal views from the same confocal z stack. All scale bars are 2 μm.

(G) Light-evoked EPSPs recorded from delayed firing GRPRexcit neurons. Left: experimental setup. Middle: superposition of 10 consecutive light-evoked EPSPs. Right: EPSP amplitudes of 15 cells.

(H) Same as (G) but tonic firing GRPRinhib neurons.

(I) Categorical scatterplot showing probabilities of light-evoked action potentials in different GRPR neuron subclasses (n = 30 cells from 28 animals). One-way ANOVA followed by Bonferroni post hoc test. F(2,28) = 9.48. p = 0.0007.

All error bars indicate SEM. Circles denote values of individual cells.