The GnRH system in an southamerican teleost, the pejerrey, Odontesthes bonariensis.

SOMOZA GM; GUILGUR , LG; MIRANDA, LA; LOPEZ, GC

Calgary

Congreso; VI International Symposium on Fish Endocrinology; 2008

ISFE

Until today a total of 14 GnRH structural variants have been isolated and characterized from vertebrate nervous tissue. Fish harbor the highest diversity in GnRHs among vertebrates: 8 of the described GnRH variants have been characterized and/or detected in teleosts and six are exclusive of this lineage. All fish species analyzed to date are known to express two or three different forms of GnRH. The GnRH variant related to the control of pituitary gonadotropes (type I or GnRH-I, first characterized in mammals), and the most conserved form of GnRH (GnRH-II). If a third form is present, this is a fish-specific GnRH variant, so far only described for teleosts (type III or GnRH-III). It is now well accepted that these three forms of GnRH are present not only in late but also in early evolved bony fishes. In these cases, GnRH-II is expressed by midbrain neurons, a species-specific GnRH, GnRH-I, is present mainly in the preoptic area and the hypothalamus, and GnRH-III is mainly localized in the terminal nerve ganglion. The distribution of these forms in different clusters of cell bodies prompted some authors to suggest the existence of three different GnRH systems with distinct physiological functions in fish. However, except for the hypophysiotropic function of the preoptic-hypothalamic GnRH-I, the physiological roles of other GnRHs are poorly known. Furthermore, the expression of these neuropeptides in vertebrates is not restricted to the central nervous system. The present work attempt to summarize the results obtained in the South American teleost, Odontesthes bonariensis, on the characterization of GnRH peptides, their cDNA, neuronatomical localization and expression pattern. The analysis of this information from an evolutionary point of view allowed us to propose different questions and scenarios.