Innervation of CGRP-positive sensory neurons in the bone. Bones were fixed, decalcified and cut on a cryostat (30 μm). Sections were then incubated with a guinea pig anti-CGRP (1:2000), followed by an incubation with goat anti-guinea pig IgG (1:500). The immunostained sections were examined under a confocal laser-scanning microscope (LSM510, Ver 3.2, Carl Zeiss). CGRP-positive sensory neurons (black) run through mineralized bone into the bone marrow. CGRP, calcitonin gene-related peptide.