Induction of ovarian growth in the red claw crayfish,Cherax quadricarinatus,by the enkephalinergic antagonist naloxone: in vivo and in vitro studies |
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Authors: | ALEJANDRA V CAHANSKY DANIEL A MEDESANI ENRIQUE M RODRÍGUEZ |
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Institution: | Department of Biodiversity and Experimental Biology, FCEyN , University of Buenos Aires , Ciudad Universitaria, Pab. II. C1428EHA, Buenos Aires, Argentina Fax: E-mail: enrique@bg.fcen.uba.ar |
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Abstract: | Summary The effects of spiperone and domperidone (dopaminergic antagonists), as well as naloxone (enkephalinergic antagonist) on ovarian growth of the crayfish Cherax quadricarinatus, were evaluated during the non-reproductive period. In vivo assays were carried out by administering these compounds by adding them to the crayfish food, and subsequently measuring the oocyte diameter (oocytes in secondary vitellogenesis). Only naloxone produced a significantly (p <0.05) higher oocyte diameter than that of the controls, suggesting that this antagonist was blocking the effects of endogenous enkcephalins on the secretion of one or more neurohormones involved in crustacean reproduction. To test this hypothesis, an in vitro incubation of ovarian pieces with thoracic ganglion (TG), a source of the gonad stimulating hormone (GSH), or eyestalk tissue (ET), the source of the gonad inhibiting hormone (GIH), with or without naloxone added to the incubation medium, was done. A significant increase of ovarian growth was observed when TG was present. Moreover, the addition of naloxone to this preparation was able to further increase the ovarian growth, presumably by preventing enkephalinergic inhibition of GSH secretion. |
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Keywords: | Cherax ovarian growth dopaminergic enkephalinergic crustaceans |
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