Immunohistochemical localization of peptide-containing nerves in human airways: age-related changes.

Bronchial reactivity changes during childhood, indicating possible changes in neural control. Nerves supplying the intrapulmonary airways were therefore studied in autopsy tissue from 14 normal infants (0 to 3.5 yr), 3 children (8.3 to 10.75 yr), and 4 adults (17 to 24 yr). An indirect immunofluorescence technique was used to study the distribution and relative number of nerve fibers containing the general neuronal markers protein gene product 9.5 and synaptophysin. Nerve subpopulations were identified using antisera to neuropeptide tyrosine, vasoactive intestine polypeptide, somatostatin, substance P, calcitonin gene-related peptide, and the enzyme tyrosine hydroxylase. Between birth and 3 yr, the distribution and relative number of immunoreactive nerves shown by both the general neuronal markers and specific antisera did not change. Neuropeptide tyrosine-immunoreactive nerves were the most common peptide-containing nerve subpopulation identified in the human lung, supplying bronchial smooth muscle, submucosal glands, cartilage, and submucosa. Other peptide-containing nerves exhibited distinct distribution patterns. Two differences in the airway innervation were identified between cases aged 0 to 3.5 yr and the older age groups. Relatively fewer peptide-containing nerves occurred in the adult bronchioli and respiratory unit, but the relative number of vasoactive intestinal polypeptide-containing nerves supplying the bronchial and bronchiolar smooth muscle was greater in the two older age groups. Given these apparent age-related differences in the number of peptide-containing nerves supplying the human airway, studies on the development of peptide receptors are indicated.