Change in Distribution and Density of CGRP, PGP 9.5, Serotonin and Chromogranin A Immunoreactivity in the Perinatal Rat Respiratory Tract.

Abstract

Distribution and density of calcitonin gene-related peptide (CGRP), protein gene product (PGP) 9.5, serotonin and chromogranin A immunoreactivity were examined in developing rat respiratory tracts from embryonic day (ED) 15 to postnatal day (PD) 60. On ED 15, the epithelium of the primitive bronchi stained positively for CGRP, PGP 9.5, serotonin and chromogranin A. CGRP, PGP 9.5, serotonin and chromogranin A positive endocrine cells extended distally along the developing bronchial trees. Cell number reached a maximum on ED 19 or ED 17. On ED 21, the clusters of endocrine cells, identified as neuroepithelial bodies (NEBs) stained positively for either CGRP or PGP 9.5 in the bronchioles, and these were observed during all stages examined. CGRP or PGP 9.5 positive nerve fibers appeared during the Perinatal periods and increased in number after birth. However, neither serotonin nor chromogranin A immunoreactivity was observed in NEBs or nerve fibers in the airway at any of the examined developmental stages.