Calcitonin gene-related peptide, enkephalin and serotonin coexist in neuroepithelial bodies of the respiratory tract of the red-eared turtle, Pseudemys scripta elegans. An immunocytochemical study.

The lungs of the red-eared turtle, Pseudemys scripta elegans, have been investigated by light-microscopical immunocytochemistry for serotonin (5-HT) and the neuropeptides calcitonin gene-related peptide (CGRP), enkephalin (ENK), bombesin, somatostatin, calcitonin and cholecystokinin. CGRP- or 5-HT-like immunoreactivity (LI) was demonstrated in neuroepithelial bodies (NEBs) and solitary neuroepithelial endocrine cells lying between the ciliated epithelial cells of the intrapulmonary bronchi, and of the primary, secondary and tertiary trabeculae. Furthermore, ENK-LI NEBs were found between the trabecular ciliated epithelial cells. No reaction was observed with antisera against bombesin, somatostatin, calcitonin, and cholecystokinin. Using consecutive sections, CGRP-LI appears to be colocalized with 5-HT-LI in NEB cells. In addition, it was demonstrated that all the ENK-LI NEBs also contain CGRP-LI, whereas only a part of the CGRP-LI NEBs reveal ENK-LI. To our knowledge this is the first demonstration of CGRP- and/or ENK-LI in pulmonary NEBs of a lower vertebrate.