Figure 3.

Labeling and analysis of the axodendritic interface. A, Low-magnification (5× objective) confocal image of a horizontal section (30 μm) from a prism-adapted owl. Small iontophoretic injections of anterograde tracer had been placed in vitro at map locations representing ∼c10° (contralateral) [Texas methyl rhodamine (TMR)] and c40° (micro-ruby). The labeled axons, which are not easily visible at this magnification, terminate primarily in ICX. Immunoreactivity for CaMKII is shown in green. The spatial density of CaMKII+ dendrites is highest in ICX. The white boxes indicate the locations of high-magnification image fields (63× objective) used for quantitative analysis. For more detailed images, see Rodriguez-Contreras et al. (2005). Scale bar, 500 μm. B, E, Representative quadrants from two separate image fields (single optical sections). CaMKII+ dendrites are shown in green, and tracer-labeled axons are shown in red. Scale bar: (in B) B–G, 5 μm. C, F, Three-dimensional reconstruction of axodendritic contacts within these quadrants. CaMKII+ dendrites (white) are contacted by one (C; purple) or three (F; blue, purple, and orange) axons. Contacts along the dendrite are indicated by yellow arrowheads. D, G, Two-dimensional optical section through dendrites and contacts from C and F. Contacts often contained several nearly abutting volume overlap objects, each of which are indicated by small numbered boxes. Each aggregate of overlap objects that occurred within 2 μm of one other was treated as a single contact (see Materials and Methods). The ICD is indicated for the most distal contacts. D, ICD, 6 μm. G, ICD, 20 μm.