Figure 4.

Low- to high-magnification images showing complex dendritic field in stratum lucidum. (A) CA3pyr dendrites (red overlays) are oriented perpendicular to the cross-fractured MF axons (aqua overlays). Dendrites run parallel to the fracture plane (diagonally from upper left to lower right), and cross-fractured MF axons run perpendicular to the fracture plane. Axons are identified by their high content of cross-fractured neurofilaments, as shown in (B). (B,C) Higher-magnification stereoscopic FRIL images of the boxed area in (A) containing a mixed synapse on a probable large CA3pyr dendritic spine near the center of the field. (C) A single gap junction was detected by the presence of 10 18-nm gold beads (labeling for Cx36) that are tightly clustered around the 56 non-crystalline E-face pits, whose center-to-center spacing is ca. 10 nm. A nearby PSD contains ca. 45 10-nm E-face particles, characteristic of glutamate receptor clusters (Harris and Landis, 1986; Rash et al., 2004, 2005), suggesting that this is a glutamatergic mixed synapse, presumably on a CA3pyr dendritic knob or spine that is postsynaptic to the large MF terminal (purple overlay). Scale bars are 0.1 μm, unless otherwise indicated.