Figure 6. Somatostatin-positive (SST+) interneurons innervate Lpar1-EGFP SPNs during early postnatal life.

(a) Widefield 473 nm blue light stimulation evoked IPSCs in SPNs at both P3–4 (n = 7) and P5–6 (n = 6) following conditional expression of Channelrhodopsin2 (ChR2) in SST+ interneurons. LED indicated by the blue line. (b) Incubation in Sr²⁺-containing ACSF resulted in asynchronous neurotransmitter release. (c) Cumulative probability plot of ChR2-evoked IPSC amplitude for control (black line; n = 13) versus Sr²⁺-containing high-divalent cation (HDC) ACSF (grey; n = 7) across P3–6; asterisk: two-sample Kolmogorov-Smirnov test: p≤0.01. (d) Comparison of early (P3–4; n=3) versus late (P5–6; n=4) IPSC amplitude in the presence of Sr²⁺-containing HDC ACSF. (e) Local and translaminar SST+ interneuron input maps onto SPNs revealed through LSPS uncaging of ATP in conjunction with conditional expression of P2x2 receptor in SST+ interneurons. (f) Local (blue) and translaminar (orange) average layer profiles for SST+ input onto SPNs.