Ab111912

For immunohistochemistry, tissue samples corresponding to precise electrode locations were fixed with 4% paraformaldehyde, cryoprotected in 30% sucrose and embedded in OCT (TissueTek) before mounting as described previously.^{30 (link)} The 20 µm sections were prepared and stored frozen until use. Immunohistochemistry was performed using VECTASTAIN® Elite® ABC Universal PLUS Kit (#PK-8200, Vector Labs). Tissue samples were probed with the following antibodies: NeuN (1:4000, #MAB337, Millipore), Iba-1 (1:1000, #019-019741, Wako), calbindin (CB) (1:800, #131767, Cell Signaling Technologies), somatostatin (SST) (1:50, #ab111912, Abcam) and parvalbumin (PV) (1:4000, #ab11427, Abcam).

Tissue sections were washed in TBS and placed in blocking solution (0.05% Triton X-100, 5% goat or horse serum in TBS) for 1 h. Endogenous peroxidases were quenched with two 30 min incubations in a peroxide–sodium azide solution (0.1% sodium azide, 0.3% H₂O₂ in TBS). Tissue was placed in primary antibody (Iba-1: 1:750, #019-019741, Wako; CB: 1:150, #131767, Cell Signaling Technologies; SST: 1:50, #ab111912, Abcam; PV: 1: 4000, #ab11427, Abcam; NeuN: 1:4000, #MAB337, Millipore; GFAP: 1:800, #MAB360, Millipore) overnight at 4°C. Immunohistochemistry was performed using VECTASTAIN Elite ABC-HRP Kit [1:250, goat anti-rabbit (#PK-6101) or horse anti-mouse (#PK-6102)]. Images were acquired with an Aperio AT2 microscope (Leica) and exported in a .tif format for subsequent analysis in ImageJ.