Figure 2.

VIP-positive interneurons at the PYR/RAD border target O–LM interneurons. (A) Maximal projection of a two-photon z-stack acquired in the CA1 region of the hippocampus of a VIP-eGFP mouse, showing bipolarly oriented VIP-positive cell bodies located at the PYR/RAD border and a dense axonal arborization in the O/A. (B) Immunofluorescence images of neurons located in PYR positive for calretinin (top) and VIP (middle) as well as their superimposition (bottom). Scale bar: 20 μ m. (C) Reconstruction of a bipolarly oriented VIP-positive cell, showing anatomical features of IS-IIIs (soma and dendrites are shown in black and axon is shown in red) and its irregularly spiking firing pattern typical for these cells. (D) Neurolucida reconstruction of a connected pair of interneurons: presynaptic IS-III (soma and dendrites are in black and axon is in red) and postsynaptic O–LM (soma and dendrites are in green, axon is in blue) and examples of unitary IPSCs evoked by two-photon glutamate uncaging (bottom left) and presynaptic spikes during paired recordings (bottom right). Black arrows indicate three putative contact sites onto O–LM dendrites. Modified from Chamberland et al. (2010).