Histochemical Study of Chromaffin Cells and Nerve Fibers in the Adrenal Gland of the Flat Snake ( Waglerophis merremii)

Abstract

The distributions of tyrosine hydroxylase (TH), protein gene product (PGP) 9.5, calcitonin gene-related peptide (CGRP), and peptide histidine isoleucine (PHI) have been examined immunohistochemically in the adrenal gland of the snake Waglerophis merremii. The morphology of chromaffin cells and the presence of ganglionic neurons in the gland revealed by means of the glutaraldehyde-silver technique and electron microscopy are also described. Two distinct types of TH-immunoreactive (-IR) cells are present in the dorsal noradrenergic ribbon: small chromaffin cells and a larger type identified as ganglionic neurons. Small, mostly round or fusiform cells often displayed long processes. Ganglionic cells, arranged in patches, had long processes entering the cortex of the gland. Chromaffin adrenergic cells, forming small groups of 4-7 cells, were scattered within the interrenal tissue and had a wide variety of shapes with processes that appeared to contact other chromaffin cells. Bundles of PGP 9.5-IR fibers occurred in the subcapsular zone of the adrenal gland with fibers entering the cortex and dorsal noradrenergic ribbon of the gland. Thick and thin TH-IR fibers were seen. Thick TH-IR fibers were nonvaricose and appeared to originate mainly in ganglionic neurons. Thin TH-IR fibers with small varicosities were numerous in the interrenal tissue and were frequently seen between clusters of adrenergic cells in close apposition to cortical cells and vessels. CGRP-IR fibers were present throughout the entire adrenal gland, whereas PHI-IR fibers had a preferential distribution in the interrenal tissue. Both CGRP- and PHI-IR fibers were closely associated with vessels and cortical cells.