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. 2020 Mar 31;7(2):ENEURO.0084-20.2020. doi: 10.1523/ENEURO.0084-20.2020

Figure 2.

Figure 2.

Selective targeting of CA2 for Gi-DREADD expression and CA1 for recording. Amigo2-icreERT2 mice were infused bilaterally with AAV-hSyn-DIO-hM4Di-mCherry, treated with tamoxifen, and implanted with NeuroNexus A1x32 silicone probes. A, Co-expression of Cre-dependent hM4Di-mCherry and RGS14, a marker for CA2 pyramidal cells, in the hippocampus. B, High magnification image showing the expression pattern of (i) hM4Di-mCherry in CA2, (ii) RGS14 in CA2, and (iii) merged images. No evidence of hM4Di-mCherry expression was found outside of the RGS14-expressing region. C, Expression of Cre-dependent hM4Di-mCherry and WFS1, a marker for CA1 pyramidal cells, across the hippocampus. D, High-magnification image showing the expression pattern of (i) hM4Di-mCherry in CA2, (ii) lack of WFS1 in CA2, and (iii) merged images. No evidence of mCherry colocalization with WFS1 was observed. E, Expression pattern of hM4Di-mCherry across the rostral to caudal extent of CA2. F, Schematic diagram of NeuroNexus A1x32 probe detailing probe dimensions. G, Ripple-filtered (100–300 Hz) LFPs across the CA1 layers. The channel with the maximal amplitude of putative ripples was designated as located in the pyramidal cell layer. H, At the end of experiments, an electrolytic lesion was made on the bottom channel of the electrode and sections were processed by IHC to highlight IBA1, a marker for activated microglia. Representative recording locations in CA1 were reconstructed based on IBA1 staining and putative ripple oscillations. Scale bars = 200 μm (A, C, H), 50 μm (B, D), and 1 mm (E).