Neuronal organization of the melanin-concentrating hormone system in primitive actinopterygians: Evolutionary changes leading to teleosts

Baker, B. I. and Bird, D. J. (2001) Neuronal organization of the melanin-concentrating hormone system in primitive actinopterygians: Evolutionary changes leading to teleosts. The Journal of Comparative Neurology, 442 (2). pp. 99-114. ISSN 0021-9967

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Publisher's URL: http://dx.doi.org/10.1002/cne.10074

Abstract

Hypothalamic melanin-concentrating hormone (MCH) neurones occur in all vertebrates and have an apparent neuromodulatory role. In teleost fish, however, MCH is used also as a neurohypophysial hormone, controlling skin color, and as a hypophysiotrophic peptide. This work describes the central location of immunoreactive MCH perikarya and their projections to the pituitary in a range of ancestral fish to determine the phylogenetic stage when the peptide adopted these roles. In all actinopterygians examined, including polypteriformes, chondrosteans, holosteans, and teleosts, immunoreactive fibers were abundant in the median eminence or, in the case of teleosts, within the pars distalis itself, suggesting MCH acquired a hypophysial regulatory role early in vertebrate evolution. MCH fibers appeared to be absent from the posterior neurohypophysis of the polypteriform Calamoichthys but were evident in this region in the chondrostean Acipensor, the holosteans Lepisosteus and Amia, and all teleosts, suggesting its use as a neurohypophysial hormone. The ability of MCH to induce skin pallor seems to have arisen at a later stage, probably in the preholosteans. This hormonal role coincides with the migration of MCH perikarya away from the ventricular surface and their enlargement into magnocellular neurones. In the higher teleosts, magnocellular hypothalamo-neurohypophysial neurones predominate in size and number, whereas smaller periventricular MCH neurones associated with the paraventricular organ, that are prominent in lampreys, early actinopterygians and tetrapods, are reduced in teleosts. The data suggest that, in teleost fish, earlier functions of the peptide may have become subordinate to its novel pigmentary role.

Item Type:Article
Additional Information:Equal co-author. Review of Baker and Bird's 6 year collaboration following Baker's discovery of a new fish hormone. Article plots distribution of cells that produce the hormone in selected fish species representative of stages in vertebrate evolution. This hormone has been found in humans with implications for stress and appetite.
Uncontrolled Keywords:neurohypophysial hormone, hypophysiotrophic peptide
Faculty/Department:Faculty of Health and Applied Sciences > Department of Biological, Biomedical and Analytical Sciences
ID Code:7011
Deposited By: H. Hammond
Deposited On:10 Aug 2010 07:35
Last Modified:12 Aug 2013 07:59

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