Changes in enkephalin and neuropeptide Y-like immunoreactivity in rabbit chromaffin tissues during perinatal development

Neuropeptide Y immunohistochemistry and ultrastructure of developing chromaffin tissue in the cloudy dogfish, Scyliorhinus torazame (Chondrichthyes, Elasmobranchii)

Ontogenetic changes in neuropeptide Y-like immunoreactivity (NPY-LI) were studied in chromaffin tissue of the cloudy dogfish, Scyliorhinus torazame. In adults and post-hatching juveniles, NPY-LI was demonstrated in chromaffin cells, but not in ganglion cells and supporting cells. Immunoreactive fibers were also found in the axillary body (the major chromaffin tissue) of the adult fish. During the embryonic period, NPY-LI was found at first in chromaffin tissue in the 34-mm stage. In this stage, cells in the periphery of the tissue were positive for NPY. Afterwards, changes were not observed in the topography and relative dominance of labelled cells in the tissue. Transmission electron microscopy of chromaffin tissue of the 26-mm stage showed an early phase of histogenesis in rudimental cell clusters composed of agranular cells and a few granular cells, i.e. pheochromoblasts. In the 43-mm stage, differentiation of the chromaffin tissue enabled ultrastructural classification of adrenalin-producing cells, noradrenalin-producing cells, ganglion cells, supporting cells, and unmyelinated nerve fibers. These results suggest that in the dogfish the appearance of NPY-LI in the developing sympathoadrenal system is related to differentiation of chromaffin cells.

Effects of acute stress on the contents of catecholamines and neuropeptides in chromaffin tissues of the newborn rabbit

The neuropeptides enkephalin (ENK), galanin (GAL) and neuropeptide Y (NPY) are abundantly expressed in the paraaortic body (PAB) and adrenal glands of the newborn rabbit. To examine whether these neuropeptides are affected by acute stress, we exposed neonatal rabbits to asphyxia, insulin-induced hypoglycemia, and reserpine. Asphyxia, caused by rebreathing for 60 min in an airtight box, reduced the content of catecholamines (CAs) in the adrenal glands and increased ENK-like immunoreactivity (-LI) in the PAB. Insulin-induced hypoglycemia reduced the content of CAs as well as ENK-LI in the adrenal glands. Reserpine caused a marked depletion of the CAs both in the PAB and in the adrenal glands. In contrast, reserpine did not cause any change in the contents of the neuropeptides in either organ. These data indicate that tissue levels of the neuropeptides GAL-LI and NPY-LI, coexisting with CA in the PAB and the adrenal glands, are not biochemically affected by asphyxia, hypoglycemia or reserpine, whereas tissue levels of ENK-LI are reduced by hypoglycemia and, to some extent, are increased by asphyxia. Furthermore, even the CAs in the PAB were unaffected by asphyxia and hypoglycemia. Also, while reserpine reduces CA content, peptide levels are unaffected.