Figure 3. Quantitative difference in fascicle size and number of E16.5 CB₁R KO thalamocortical axons.

(A–B) Sample images show L1-NCAM (L1) and CTFL double labeling with coronal brain sections taken from the rostral forebrain areas (as indicated in Figures 1) of control (A) and E16.5 CB₁R KO mice (B). Aberrant axonal fascicles were detected by both L1 and CTFL immunoreactivity at the PSPB (B1–B3; arrows heads indicate large fascicles and arrows indicate misrouted axons; two misrouted axons were high-lighted with dashed green lines placed slightly below the fibers observed). The color of single channel fluorescence images was inverted to provide better illustrations. (C–H) The diameter and number of CTFL-positive TCA fascicles were quantified in a 400×100 µm² area located in the striatum (white dashed rectangles in C, D, panels 1–2) and 100 µm away from the PSPB (yellow dashed lines in C, D). These measurements were conducted in 3–5 different PSPB areas per animal and 3 animals per genotype. (E–H) Both the diameter and number of TCA fascicles are significantly different between CB₁R KO and control mice. There was a shift towards larger fascicles in the distribution of thalamocortical axon fascicle size in CB₁R KO mice (E, F). The number of fascicles per area measured was significantly reduced (G), while the mean fascicle size was significantly increased (H) in CB₁R KO mice compared to control. * Student’s t-test, p <0.05.