Figure 2.

The vast majority of perisomatic GABAergic inputs onto the principal cells originates from boutons co-expressing parvalbumin (PV) and calbindin (Calb) or CB₁ cannabinoid receptors. (A) Multicolor single plane confocal images taken from immunostaining against Kv2.1 (to delineate the perisomatic region of PCs), VGAT, CB₁, and PV. Far right: the reconstruction of a Kv2.1-immunostained neuron receiving GABAergic inputs. Arrows and dots in magenta point to VGAT/PV-immunostained boutons, an arrowhead, and a triangle in magenta mark an only PV-containing bouton, arrows, and dots in yellow indicate VGAT/CB₁-immunopositive varicosities, arrowheads, and triangles in yellow mark only CB₁-immunoreactive boutons and an arrow and a dot in blue show an only VGAT-immunolabeled bouton forming close appositions with a Kv2.1-immunostained neuron. (B) Ratio of boutons expressing PV, CB₁, and VGAT only on the Kv2.1-immunostained soma and proximal dendrites of neurons. (C) Multicolor single plane confocal images taken from immunostaining against Kv2.1, Calb, CB₁, and PV. White arrows point to boutons co-expressing Calb and PV forming close appositions with a Kv2.1 immunostained soma membrane segment, while a yellow arrow indicates a CB₁-immunoreactive varicosity lacking Calb immunolabeling. (D) Ratio of PV- or CB₁-expressing boutons immunoreactive for Calb on soma or proximal dendrites. Numbers of boutons evaluated are indicated for each column. Scale bars, 10 μm in (A), 1 μm in (C).