Calcitonin Gene-Related Peptide–Immunoreactive Nerves and Neuroendocrine Cells after Lung Transplantation in the Rat

Bronchial innervation is interrupted at lung transplantation. Nerve fibers with cell bodies above the section, such as sensory C fibers, should degenerate. Using histofluorescence, we evaluated calcitonin gene-related peptide (CGRP) immunoreactivity in syngeneic Lewis rats 1 and 5 mo after unilateral lung transplantation and in controls. CGRP-immunoreactive (IR) neuroendocrine cells were located within the epithelium of large and small bronchi. At 1 mo after transplantation, their number had significantly increased in large bronchi and had normalized 5 mo after transplantation. The density of CGRP-IR fibers in control lungs gradually decreased from large (0.35 ± 0.02 μm/μm basal lamina) to small (0.23 ± 0.02) and peripheral bronchi (0.12 ± 0.01). At 1 mo after lung transplantation, few CGRP-IR fibers were observed in large bronchi (0.17 ± 0.02), fewer in small bronchi (0.04 ± 0.01) (P < 0.01), and none in peripheral bronchi. At 5 mo after lung transplantation, transplanted lungs still had fewer CGRP-IR fi...