Figure 1.

PD-1 is Required for GABAergic Signaling in SDH Neurons in Spinal Cord Slices

(A–C) GABA-induced currents in SDH lamina II neurons of WT and Pd1^−/− mice. (A) Left: experimental setup for local perfusion of GABA (1 mM) in spinal cord slices. Right: representative traces of currents evoked by transient GABA perfusion.

(B) Quantification of GABA-induced unit currents from WT and Pd1^−/− mice. n = 13 and 16 neurons from 4 animals.

(C) Dose-response curve plotting the average amplitude of GABA-induced currents. The curves were drawn according to the Hill equation. Values in parentheses denote the number of recorded neurons per group, each taken from 3–4 animals per group.

(D and E) GABA-induced currents in lamina II neurons of spinal cord slices from SST^td−Tomato reporter mice (D) and vGAT^td−Tomato reporter mice (E). Left top: experimental setup for GABA perfusion, as in (A). Left bottom: epifluorescence image of a spinal lamina II SST⁺ neuron or vGAT⁺ neuron with a recording pipette. Middle: traces of GABA (1 mM)-induced currents after incubation with IgG or Nivo (300 ng/mL, 2 h). Right: quantification of GABA-evoked unit currents. n = 11 (IgG, 6 mice, D); n = 7 (Nivo, 3 mice, D); n = 12 (IgG, 5 mice, E); n = 9 (Nivo, 4 mice, E).

(F–H) Blue-light-induced currents in spinal cord slices of vGAT^Ai32 mice. (F) Schematic of experimental setup. vGAT⁺ neurons were stimulated with blue light (473 nm, 4 ms) to evoke endogenous GABA release, and postsynaptic currents were recorded from vGAT⁻ neurons in lamina II (G) and lamina I (H) neurons. (G) Left: representative traces of light-induced currents from vGAT⁻ neurons in spinal lamina II after incubation with IgG or Nivo (300 ng/mL, 2 h). Right: unit currents of light-evoked currents (n = 8 and 12 neurons from 3 animals/group). (H) Identical setup as in (G) but performed in spinal lamina I (n = 11 and 14 from 3 animals/group).

(I and J) Dorsal root stimulation evoked currents in spinal cord slices from WT and Pd1^−/− mice. (I) Left: experimental setup. An electrical stimulus was applied to the spinal dorsal root to evoke GABA-evoked IPSCs. Right: representative traces of evoked IPSCs from WT and Pd1^−/− mice. (J) Quantification of the amplitude of the evoked IPSCs from WT and Pd1^−/− mice. n = 8 and 13 neurons recorded from 4 and 3 animals, respectively.

(K–L) Same setup as in (A and B), but using the GABA_AR selective agonist THIP (1 mM; n = 11 neurons per group from 3 animals per group).

Gray arrowheads indicate the application of GABA or THIP. Blue arrowheads indicate the blue light stimulus. V_H = 0 mV. Unpaired two-tailed t test. Each graph indicates the mean ± SEM.