Figure 4.

LII CB⁺ Neurons Target Multiple Cell Types in LII of the Contralateral MEC

(A) Retrogradely labeled LII and LIII neurons following CTB injection into the contralateral MEC (sagittal section).

(B) Most retrogradely labeled neurons (blue) in LII were CB⁺ (red) and localized in CB⁺ islands (the confines of this island are indicated by a dashed line). The Inset is a higher magnification of the indicated area (white square) and shows a CTB⁺/CB⁺ neuron. Scale bar, 100 μm.

(C) Confocal image of injection site in LII following AAV DIO-ChR2-mCherry injection into the MEC of CB^Cre mice. Scale bar, 100 μm.

(D) Sagittal MEC section showing innervation of LII following AAV DIO-ChR2-mCherry injection into the contralateral MEC of CB^Cre mice. Scale bar, 100 μm.

(E) Synaptic responses and firing pattern of a targeted SC and a FS interneuron. ChR2-mCherry-expressing axons were stimulated by 5-ms laser pulses (blue bar) and EPSCs were recorded. Excitatory and monosynaptic inputs were identified in the presence of the indicated antagonists.

Abbreviations are as follows: L, layer; CTB, cholera toxin subunit B; MEC, medial entorhinal cortex; FS, fast-spiking interneuron; and SC, stellate cell. See also Figure S6 and Table S2.