Figure 2.

Characteristics of infected interneurons in SST, VIP, and PV-Cre mice. A, SST-expressing interneurons are known to heavily innervate the distal dendrites of cortical pyramidal cells. This is evidenced by the high density of projections in superficial layers, including high axon density in layer 1. The distal dendrites of some retrogradely infected pyramidal cells are also visible extending into layer 1. RV, magenta; DAPI, cyan. This is consistent for all panels. Scale bar, 50 μm. B, Rabies-infected VIP-expressing interneurons are largely bipolar in nature, with a primary neurite extending into layer 1, and the other projecting to deeper layers of cortex. The cell bodies of these neurons are primarily found in superficial cortical layers. Scale bar, 50 μm. C, As expected from the properties of PV+ interneurons, very few projections are detected in layer 1 of PV-Cre mice following AAV and RV infection. However, there is heavy innervation of deeper cortical layers. Scale bar, 50 μm. D, Fluorescently labeled basket-type synapses are prevalent in PV-Cre mice, ringing neuronal somata in deeper layers of cortex. This is consistent with efficient targeting to PV-expressing basket cells in this mouse line. Scale bar, 25 μm.