The involvement of galanin in the reproductive cycle of sea bass

Abstract

In commercial aquaculture systems the sea bass (Dicentrarchus labrax) consistently presents high rates of precocious puberty males, which is correlated with negative aspects to aquaculture production. Preliminary data suggest that galanin (GAL), a neuropeptide associated with increased appetite, is potentially involved in the control of the reproductive cycle. Taking in account that the identification and characterization of regulators of the reproductive cycle in sea bass would be extremely beneficial to commercial aquaculture systems, the aim of the present work was the evaluation of the putative involvement of GAL in the reproductive cycle of sea bass. Dispersed pituitary cells collected from fish in different stages of the reproductive cycle were incubated with GAL and the amount of released gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH) was quantified and compared with that of control cells. In addition, the effects of GAL in cAMP production was also accessed. Our results showed that there was a peak of FSH release in September in two year-old males (pre-pubertal) in response to GAL, while there were no differences relative to control cells in November nor in January (spermiating males). No effects of GAL were induced on pituitary LH release in September and November, while in January there was a significant increase of LH release in all the concentrations tested. Galanin alone had no effect on pituitary cells cAMP production, however in cells previously stimulated with forskolin (an activator of adenylate cyclase) there was an inhibition of cAMP production by GAL, in September and October but not in January. RT-PCR allowed to detect the expression of several subtypes of galanin receptors in pituitaries collected at the analysed time points of the year. These results suggest the involvement of galanin in the reproductive cycle of sea bass.