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. Author manuscript; available in PMC: 2021 Mar 15.
Published in final edited form as: Neuropharmacology. 2019 Dec 21;165:107831. doi: 10.1016/j.neuropharm.2019.107831

Figure 1. Circuit tracing of agranular insular cortex (IC) inputs to the substantia nigra (SN).

Figure 1.

(A) Viral-mediated anterograde tracing via injection of AAV-CAMKII-ChR2-mCherry into the IC was used to map long-range projections to the SN. Channelrhodopsin-2 (ChR2)-positive fibers (pseudocolored magenta) from the IC were distributed throughout the GABA-enriched SN pars reticulata (SNpr) and dopamine dense SN pars compacta (SNpc). Nuclei were counterstained with DAPI (blue). (B-C) Injection of the fluorescent retrograde tracer Fluoro-Gold (FG) was used to confirm IC inputs to the SN, and FG-positive neurons (pseudocolored cyan) were distributed in layers 5 and 6 of the IC. Conversely, dynorphin (DYN) cells (pseudocolored magenta) are densely expressed in layer 2/3 of the IC, and do not overlap with layer 5 IC-SN projection neurons (pseudocolored cyan). Roman numerals indicate cortical layers; Cl, claustrum; CP, cerebral peduncle; ml, medial lemniscus; SNl, lateral substantia nigra