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Innervation and control of the adenohypophysis by hypothalamic peptidergic neurons in teleost fishes: EM immunohistochemical evidence
Author(s) -
Batten Trevor F.C.,
Moons Lieve,
Vandesande Frans
Publication year - 1999
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/(sici)1097-0029(19990101)44:1<19::aid-jemt4>3.0.co;2-l
Subject(s) - medicine , biology , endocrinology , somatostatin , galanin , neuropeptide , vasotocin , gonadotropic cell , somatotropic cell , hypothalamic hormones , pituitary gland , hormone , growth hormone–releasing hormone , receptor , growth hormone , pituitary hormones
Previous light microscopic studies have revealed neuropeptide‐immunoreactive neurosecretory fibers in the teleostean neurohypophysis, and ultrastructural work has reported direct innervation of endocrine cells by the terminals of fibers penetrating the adenohypophysis. This paper reviews our recent data from ultrastructural, immunohistochemical, receptor localization, and superfusion studies, which suggest a role for neuropeptides in the control of teleost pituitary secretion. We have used a combination of pre‐ and post‐embedding electron microscopic immunolabeling methods to determine which neuropeptides are present in fibers innervating the pituitaries of three species: Poecilia latipinna, Dicentrarchus labrax, and Clarias gariepinus. Numerous axon profiles with immunoreactivity for the neurosecretory peptides vasotocin and isotocin formed large Herring bodies and terminal‐like boutons in contact with corticotropic, growth hormone, thyrotropic, and pars intermedia cells. Numerous melanin‐concentrating hormone‐immunoreactive fibers and scarcer neurotensin and corticotropin‐releasing factor‐immunoreactive fibers showed similar distributions, terminating close to pars intermedia and corticotropic cells. Somatostatin, cholecystokinin, galanin, substance P, neuropeptide Y, growth hormone‐releasing factor, thyrotropin‐releasing hormone, and gonadotropin‐releasing hormone‐immunoreactivities were found in small calibre fibers penetrating among growth hormone, thyrotropic, and gonadotropic cells. These morphological findings have been supplemented by autoradiographic studies, which showed the distribution of binding sites for vasotocin, isotocin, galanin, and neuropeptide Y ligands over specific groups of pituitary cells, and superfusion studies that showed growth hormone release was stimulated by growth hormone‐releasing factor and thyrotropin‐releasing hormone, but inhibited by somatostatin. The implications of these results for neuropeptidergic control of teleostean pituitary secretions are discussed. Microsc. Res. Tech. 44:19–35, 1999. © 1999 Wiley‐Liss, Inc.