Figure 1. Relationship of astrocyte branches and capillaries to the barrels borders in cortical layer IV at medium and high magnifications.
(A) A dark field illumination image (inverted contrast) of the barrel field (BF) area of a flattened left hemisphere. The barrel borders are evident as dark septa surrounding a lighter core. Barrel rows A–E and arcs 1–5 as well as the medial–lateral and rostral–caudal axes are indicated. (B) Reconstruction of the capillaries (Cp) visualized using fluorescein dextran. Barrel borders (derived from A) marked by yellow lines, were superimposed on the drawing of capillaries. The two images were aligned using penetrating blood vessels as landmarks. (C) Fluorescent micrograph of GFAP immunostaining (CY3 conjugated) of astrocyte processes (As). The image consists of 90 tiles that were assembled together revealing the lateral distribution of the processes. (D) A reconstruction of the astrocyte processes of image C performed by manual drawing of their branches at high magnification. The borders of the barrel field (marked in turquoise) and astrocyte processes were aligned as in B. Green arrowheads indicate three barrel borders shown in enlarged view in E and F. All the images were taken from the same tissue section. (E) Enlarged florescent image of stained astrocyte processes (same as in C) showing further details of the processes. Arrow heads point to a clearly visible gap in the astrocyte distribution at three barrel boundaries. Green corners indicate the enlarged image shown in G. (F) A reconstruction of the astrocyte processes (drawn manually at high magnification) shown in E. (G) An enlarged fluorescent image view of the area bounded by the green box in E, showing the astrocyte distribution relative to the barrel borders (arrows). (H) A high magnification confocal image demonstrates the fine processes of two astrocytes at the border between barrels and septa (green arrowhead) indicated by a yellow line. The astrocyte cell bodies are indicated by yellow arrows and examples of their processes by red ones.