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. 2020 Apr 23;14:17. doi: 10.3389/fncir.2020.00017

Figure 1.

Figure 1

Cell type-specific retrograde tracing reveals long-range GABAergic projections to the olfactory bulb (OB). (A) Schematic depicting viral injection a retro2 serotype adeno associated virus expressing Cre-dependent mVenus (rAAV-Ef1α-flex-mVenus) into the OB of Vgat-Cre-expressing mice. Retrograde labeling reveals sources of synaptic input to the OB. (B) GABAergic retrograde labeling in OB with inset showing mVenus expression in the granule cell layer (GCL). (C) GABAergic retrograde labeling in a coronal section including the anterior olfactory nucleus (AON) with inset showing mVenus expression in lateral AON. (D) GABAergic retrograde labeling in a coronal section including the horizontal diagonal band of Broca (HDB) and lateral septum (LS) with insets showing mVenus expression in LS and HDB. (E) CHAT immunolabeling overlaid with GABAergic retrograde labeling in a coronal section including HDB, with inset showing lack of colocalization between CHAT+ and mVenus+ neurons in the HDB. (F) Quantification of CHAT+, mVenus+, and colocalized neurons in the HDB normalized to DAPI from single 40 μm thick sections. Points reflect cell counts from individual animals. N = 10 mice. Error bars are SE. One sample Wilcoxon rank-sum test. *p < 0.05, **p < 0.01. (G) Retrograde labeling in a coronal section including the ventral subiculum (vSUB) with inset showing sparse mVenus expression in vSUB. (H) mVenus+ cell counts by brain region from single 40 μm thick sections normalized to the number of DAPI+ cells in each region. Points reflect cell counts from individual animals. N = 8–14 mice. Error bars are SE. One sample Wilcoxon rank-sum test. *p < 0.05, **p < 0.01, ***p < 0.001. Scale bars are 100 μm unless otherwise specified.