Studies on the mode of action of NPY on maturational gonadotropin (GtH) from perifused rainbow trout pituitary glands

International audienceThe action of neuropeptide Y (NPY) and gonadotropin releasing hormone (s-GnRH) have been compared on the release of gonadotropin (GtH) by perifused rainbow trout pituitary glands sampled from freshly ovulated female rainbow trout. We have already demonstrated that NPY stimulated the secretion of GtH in vitro. The pituitary responses to s-GnRH and NPY were similar either after repeated 10 min infusions or a one hour prolonged application. In both cases, after the first application, the pituitary did not responded to subsequent secretagogues stimulations, and appeared to be desensitized. The stimulatory action of s-GnRH was partly inhibited (60%) by LH-RH antagonist (DpGlu1, DPhe2, DTrp3-6) LH-RH, which completely inhibited the response to NPY in perifused pituitary glands sampled from freshly ovulated females, but did not modify the response of pituitaries taken from vitellogenic animals in which NPY induced a transient inhibition of the GtH secretion. These results may indicate that the mode of action of NPY would differ between vitellogenic and matured animals. NPY also stimulated the GtH secretion from perifused pituitary dispersed cells prepared from pituitaries taken from freshly ovulated rainbow trout, indicating that NPY may act directly on the pituitary gonadotropic cells to stimulate GtH secretion

Effect of osmotic pressure on prolactin release in rainbow trout: in vitro studies

International audienceTo investigate a possible effect of osmotic pressure on prolactin (PRL) release in rainbow trout, we developed a technique for in vitro perifusion of trout pituitaries. Changes in osmotic pressure similar to those observed in fish plasma during transfer experiments did not induce significant modifications of PRL release. In contrast, high-amplitude variation of osmotic pressure resulted in clear modifications of PRL secretion: hyperosmotic medium caused a reduction in PRL release, while infusion of hyposmotic medium induced a transitory increase in PRL release. By using different concentrations of mannitol, we found that the modifications of prolactin secretion could not be ascribed to alterations of the ionic composition of the medium but actually resulted from variations in the osmotic pressure of the incubation medium. In further experiments osmotic pressure was decreased from 300 to 220 mOsm/kg or from 400 to 300 mOsm/kg; a similar transitory increase in PRL release was observed. Measurement of gonadotropin (GtH) in the perifusion effluent medium showed that PRL and GtH secretion followed similar patterns. Thus, our results suggest a possible mechanical effect of wide changes in osmotic pressure on pituitary cell membranes. These data indicate that the rainbow trout differs notably from nonsalmonid teleost species thus far studied in the lack of sensitivity of its PRL cells to osmotic pressure

Localization characterization and neuroendocrine action of NPY in the trout brain

International audienc

KP10, the shortest peptide of the kisspeptin family, is a very minor form in the sheep hypothalamus: an immunological study

International audienc

Neuropeptide Y in the brain and pituitary of the trout: localization, characterization, and action on GTH secretion

International audienc

Characterization of the Kiss/KissR systems in a teleost fish. Potential interactions with the GnRH systems and leptin receptors in the brain of zebrafish

National audienc

Molecular forms of kisspeptin present in the sheep hypothalamus: a semi-quantitative study

National audienc

Expression de l'EM66, un nouveau peptide dérivé de la sécrétogranine II, dans l'hypothalamus de la gerboise et du rat: effet de la privation de nourriture

National audienc

VIP and PACAP induce selective neuronal differentiation of mouse embryonic stem cells

International audienc

Biochemical characterization and immunocytochemical localization of EM66, a novel peptide derived from secretogranin II, in the rat pituitary and adrenal glands

International audienc