GnRH systems of Cichlasoma dimerus (Perciformes, Cichlidae) revisited: a localization study with antibodies and riboprobes to GnRH-associated peptides

Abstract

The distribution of cells that express three prepro-gonadotropin-releasing hormones (GnRH), corresponding to salmon GnRH, sea bream GnRH (sbGnRH), and chicken II GnRH, was studied in the brain and pituitary of the South American cichlid fish, Cichlasoma dimerus. Although the ontogeny and distribution of GnRH neuronal systems have previously been examined immunohistochemically with antibodies and antisera against the various GnRH decapeptides, we have used antisera against various perciform GnRH-associated peptides (GAPs) and riboprobes to various perciform GnRH+GAPs. The results demonstrate that: (1) the GnRH neuronal populations in the forebrain (salmon and sea bream GAPs; sGAP and sbGAP, respectively) show an overlapping pattern along the olfactory bulbs, nucleus olfacto-retinalis, ventral telencephalon, and preoptic area; (2) projections with sGAP are mainly located in the forebrain and contribute to the pituitary innervation, with projections containing chicken GAP II being mainly distributed along the mid and hindbrain and not contributing to pituitary innervation, whereas sbGAP projections are restricted to the ventral forebrain, being the most important molecular form in relation to pituitary innervation; (3) sbGnRH (GnRH I) neurons have an olfactory origin; (4) GAP antibodies and GAP riboprobes are valuable tools for the study of various GnRH systems, by avoiding the cross-reactivity problems that occur when using GnRH antibodies and GnRH riboprobes alone.

Identification of immunoreactive FSH and LH cells in the cichlid fish Cichlasoma dimerus during the ontogeny and sexual differentiation

“…Moreover, in the tilapia it was clearly demonstrated the FSH and LH expressing neurons also express AVT, and this neurohypohysial hormone was synthesized in preoptic neurons, which are strongly related with the control of some reproductive behaviors (Demski and Sloan 1985;Foran and Bass 1999;Parhar et al 2003). Interestingly, FSH and LH neurons are expressed in POA regions that also express GnRH1 and GnRH3 in this species (Pandolfi et al 2005). Although this occurs in morphological different neurons, it is possible that some synapsis between GnRH and FSH and/or LH neurons take place.…”

“…Ten pituitaries and two ovaries were homogenized in 1 ml of Tris-HCl buffer 50 mM pH 7.4 with 10 ll of protease inhibitor cocktail (Sigma, Saint Louis, MO). Samples were processed for SDS-PAGE followed by Western blot as was previously described for this species (Pandolfi et al 2005). The primary antisera dilutions were 1:2,000 for anti-Fh (50-60) bFSH and 1:4,000 for anti-Fh (91-106) bLH.…”

Effect of salmon melanin-concentrating hormone and mammalian gonadotrophin-releasing hormone on somatolactin release in pituitary culture of Cichlasoma dimerus

“…Salmon and mostly seabream GnRH fibers innervate the pituitary at the pars intermedia level together with MCH fibers (Pandolfi et al 2003(Pandolfi et al , 2005. We have compared the distributions of GnRH-ir fibers and MCH-ir fibers at the pars intermedia level.…”

“…This finding is consistent with results obtained in the barfin flounder, where chicken GnRH-II-ir fibers lie in close contact with MCH-ir cell bodies in the nucleus lateralis tuberis of the hypothalamus (Amiya et al 2008). In C. dimerus, chicken GnRH-II-ir, salmon GnRH-ir, and seabream GnRHir fibers are widely distributed in the brain, including the nucleus lateralis tuberis (Pandolfi et al 2005). In the barfin flounder, chicken GnRH-II-ir levels in fish adapted to black tanks are higher than in those adapted to white tanks (Amiya et al 2008).…”

“…This cichlid shows a marked color display during stress, mating, and environmental changes. Among other studies, the localization of SL-immunoreactive (ir) cells (Pandolfi et al 2001a, b) and the expression of GnRH, MCH, and alpha-melanocyte-stimulating hormone (α-MSH) cells (Pandolfi et al 2002(Pandolfi et al , 2003(Pandolfi et al , 2005 have been reported for C. dimerus.…”