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Trends in Comparative Biochemistry & Physiology   Volumes    Volume 1  Issue 1
Gonadotropin - releasing hormone structure and the neuroendocrine regulation of reproduction in the cartilaginous fish
David A. Lovejoy
Pages: 509 - 519
Number of pages: 11
Trends in Comparative Biochemistry & Physiology
Volume 1  Issue 1

Copyright © 1993 Research Trends. All rights reserved

The cartilaginous fish are considered to be the phylogenetically oldest jawed vertebrates. In spite of their morphological conservation during 400 million years of evolution, expression of gonadotropin-releasing hormone (GnRH) structural variants in the brain varies profoundly among species. The dominant form of this neuropeptide is [His5Trp7Tyr8]-GnRH (chicken GnRH-II) and may have been the original hypothalamic gonadotropin-releasing factor in jawed vertebrates. Indeed, both this form and the related [His5Trp7Leu8]-GnRH (dogish GnRH), are potent at gonadotropin release in mammalian-based systems. The presence of GnRH-binding substances and high concentrations of chicken GnRH-II in the systemic blood suggest the chondrichthyan system evolved to transport GnRH to the gonadotropes via the systemic circulation.
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