Distribution of substance P-immunoreactive and calcitonin gene-related peptide-immunoreactive nerves in normal human lungs.

The distribution of substance P (SP)-immunoreactive (IR) and calcitonin gene-related peptide (CGRP)-IR nerves in normal human lungs was immunohistochemically investigated. SP-IR and CGRP-IR nerves were found in lamina propria and adjacent to blood vessels, and also in some of the ganglia and nerve bundles in the submucosal area. Comparison of serial consecutive sections revealed that SP-IR and CGRP-IR nerves represented similar distribution patterns. CGRP-IR nerves were scarce in bronchial smooth muscles, whereas SP-IR nerves were always present therein. Neither SP-IR nor CGRP-IR nerves were found, however, among submucosal glands or in alveolar septa. These localization patterns were closely related to the functions of SP and CGRP in normal lungs.