Figure 1.

BDNF expression within the DRG and spinal dorsal horn. (a and c) Under normal circumstances, modest BDNF immunoreactivity is observed within lumbar DRG and superficial dorsal horn. (e, bold arrow) Constitutively expressed BDNF colocalizes with the neuropeptide calcitonin-gene-related peptide (CGRP) and is present mainly within small-diameter sensory neurons. These neurons mostly do not express trkB. BDNF expression is regulated by NGF. (b and d) After systemic NGF treatment, BDNF immunoreactivity is enhanced within lumbar ganglia and dorsal horn. (e, light arrow) After NGF treatment, ≈80–90% of trkA-expressing sensory neurons contain BDNF immunoreactivity. These neurons coexpress CGRP.