Involvement of the hypothalamic-pituitary-interrenal axis in the antistress activities of Tenebrio molitor Larvae in zebrafish

In this study, the antistress effects of the water extract of Tenebrio molitor larvae (WTML) were investigated. To determine the effects of WTML on fish stress, changes in whole-body cortisol levels and behaviour were monitored in zebrafish (Danio rerio). To induce physical stress, we used net handling stress (NHS). Fish were treated with WTML for 6 min before exposure to stress. Then, the fish were used for evaluation via behavioural tests, including novel tank tests and open field tests, or sacrificed for collection of the whole body fluid. Increased anxiety-like behaviours in the novel tank test and open field test under stress were significantly and concentration-dependently recovered after treatment with WTML (p < 0.05). Moreover, compared with the normal group, which was not induced by NHS, the whole-body cortisol levels of the control group were significantly increased after induction by NHS. Compared with the control group, pretreatment with WTML at concentrations of 25, 50 and 100 mg/L for 6 min significantly prevented the increase in whole-body cortisol levels induced by NHS (p < 0.05). In addition, challenge studies showed that WTML completely blocked the effects of intraperitoneally-injected adrenocorticotropin hormone (ACTH; 0.2 IU/g) on cortisol secretion. These results suggest that WTML may be a good antistress candidate, and that its mechanism of action may be related to its positive effects on cortisol release.