Vasotocinergic system versus stress response: effects of cortisol injection in the gilthead sea bream (Sparus aurata)

Abstract

The influence of cortisol treatment on osmoregulation, metabolism and the vasotocinergic system in gilthead sea bream (Sparus aurata) was evaluated. Specimens from control group were injected intraperitoneally with slow release implants of coconut oil alone, while animals from cortisol group were injected with coconut oil containing cortisol (50 ¿g¿g-1 body weight). Plasma cortisol, glucose and lactate levels increased in cortisol-treated fish. An enhanced hypoosmoregulatory capacity of cortisol-implanted fish is suggested by the decrease on osmolality at 12 h post-implant. Specimens from control group increased plasma AVT levels at 12 hours post-implant, while no changes were observed in hypothalamic expression of pro-vasotocin (pro-VT) and pituitary storage of AVT. In cortisol group, hypothalamic pro-VT expression (at 12 hours and 1 day) and AVT pituitary storage (at 3 days) enhanced, while plasma AVT levels decreased (at 3 and 10 days). We showed in this study the relationship between both stress and the vasotocinergic system in S. aurata.