Figure 2. The morphology and density of IGLEs in the stomach (A, C, E) and intestine (B, D, F). The morphology of IGLEs in the stomach was normal in INT-BDNF−/− mice. IGLEs observed in the stomachs of both controls (A) and mutants (C) displayed the characteristic pattern of IGLE innervation, which can be seen as vagal afferent axons giving rise to the leaf-like IGLEs composed of numerous, densely packed, punctate endings. There were no differences in IGLE density between any of the genotypes or between any of the stomach compartments (INT-BDNF−/−, n = 9; INT-BDNF+/−, n = 9; control, n = 12; E). In the intestine, although the general innervation pattern and IGLE structure was similar in controls (B) and INT-BDNF−/− mice (D), the IGLE terminals appeared larger and more numerous in mutants. Furthermore, fiber bundles often appeared to contain more fibers or be larger in diameter in mutants. Quantification of IGLE density in the first 8 cm of the small intestine demonstrated a significant 40% increase in IGLE density in INT-BDNF−/− mice compared with controls (p < 0.05; group sizes were the same as for the stomach; F). This increase in IGLE density was evenly distributed across the 0–4 and 4–8 cm segments of the proximal small intestine. Arrows in A–D indicate IGLEs (double arrow in D indicates a tightly packed group of small IGLEs). Arrowheads in B and D indicate vagal sensory axon bundles. Open arrowhead in D points to a single vagal afferent axon. Scale bars: (in C) A, C, 150 μm; (in D) B, D, 50 μm.