INVESTIGADORES
CANOSA luis fabian
congresos y reuniones científicas
Título:
Role of GnRH variants in the LH secretion in the goldfish
Autor/es:
CANOSA LF; STACEY N; PETER RE
Lugar:
Calgary
Reunión:
Simposio; 6TH International Symposium on Fish Endocrinology; 2008
Resumen:
As many as three gonadotropin-releasing hormone (GnRH) systems can co-exist in the vertebrate brain. The GnRH-I system, present in forebrain, controls LH secretion and can have different GnRH peptides in different species. The GnRH-II system, invariably represented by chicken GnRH-II (cGnRH-II), is present in midbrain and can be involved in sexual behavior. Several teleosts also have a GnRH-III system, invariably represented by salmon GnRH (sGnRH), and also present in forebrain. Although the brain of goldfish (Carassius auratus) contains both cGnRH-II and sGnRH, the cGnRH-II is found not only in midbrain (the site of the GnRH-II system) but also in forebrain. This apparent deviation from the typical vertebrate pattern raises the question of whether forebrain sGnRH or cGnRH-II represents the GnRH-I (LH regulating) system of goldfish. To answer this, we first monitored GnRH gene expression in female goldfish brain during ovulation and spawning that was induced naturally by manipulating temperature and spawning substrate (vegetation). Forebrain sGnRH mRNA levels increased coincident with onset of the preovulatory LH surge (approximately 8 hours prior to spawning), whereas cGnRH-II mRNA levels, both in forebrain and midbrain, increased during spawning. To further distinguish between the GnRH changes associated with LH increase and the GnRH changes associated with behavior, we next monitored GnRH gene expression during spawning behavior induced by injecting nonovulated females with prostaglandin F2a (PG), the endogenous postovulatory trigger for female spawning behavior. As was seen in natural spawning, forebrain and midbrain cGnRH-II mRNA levels increased during PG-induced spawning, whereas forebrain sGnRH-II mRNA levels did not. The simplest interpretation of these results is that, in goldfish, forebrain sGnRH represents the GnRH-I (LH regulating) system whereas forebrain and midbrain cGnRH-II represents the GnRH-II (reproductive behavior) system. Acknowledgements: Supported by: NSERC Canada operating grants to REP. LFC was the recipient of an International Post-doctoral fellowship from CONICET, Argentina.