Figure 1.

Motor Cortex SOM⁺ GABAergic Neurons Innervate the Striatum

(A) Schematic drawing of the injection site and the location of long-range projections in the striatum shown in (B). Viral constructs encoding ChR2-mCherry were injected into the motor cortex of SOM^Cre mice.

(B) Bright-field images of DAB-stained sections showing the injection site in the motor cortex (left) and mCherry-labeled axons in the striatum (center) following AAV DIO ChR2-mCherry injection into the motor cortex of SOM^Cre mice. A higher magnification of the boxed area is shown on the right.

(C and D) Confocal images showing a retrogradely labeled area (C) following injection of the retrograde tracer CTB647 into the striatum and a retrogradely labeled GABAergic SOM⁺ neuron in the motor cortex, visualized via FISH for Sst and Gad1/2 (D).

(E–H) SOM⁺ projecting neurons were identified by retrograde tracing with SADΔG-EGFP(EnvA) rabies virus. TCB was expressed Cre-dependently in the motor cortex of SOM^Cre mice, and rabies virus was injected into the striatum. (E) shows differential interference contrast (DIC) and epifluorescent images of a retrogradely labeled TCB⁺ neuron in the motor cortex with the corresponding firing pattern shown in (F). (G) shows a confocal image of a retrogradely labeled TCB⁺ neuron in M1 immunostained for EGFP and SOM with the corresponding morphological reconstruction shown in (H).

Str, striatum. See also Figure S1 and Tables S1 and S2.