Objective:

2

To determine the effects of

Hydrangeae Dulcis Folium

(EHDF) on physical stress

changes in the whole-body cortisol level and behaviour in zebrafish (

Danio rerio

).

Methods:

2

One hundred and seventy-four fish were randomly divided into 4 [adrenocorticotropin hormone (ACTH) challenge test: 4 fish per group] or 6 groups (behavioural test: 10–12 fish per group

whole-body cortisol: 4 fish per group). Net handling stress (NHS) was used to induce physical stress. Fish were treated with vehicle or EHDF (5–20 mg/L) for 6 min before they were exposed to stress. And then

fish were sacrificed for collecting body fluid from whole-body or conducted behavioural tests

including novel tank test and open field test

and were evaluated to observe anxiety-like behaviours and locomotion. In addition

to elucidate the mode of action of the anti-stress effects of EHDF

ACTH (0.2 IU/g

i.p.) challenge test was performed.

Results:

2

The increased anxiety-like behaviours in novel tank test and open field test under stress were prevented by treatment with EHDF at 5–20 mg/L (

P

<

0.05). Moreover

compared with the unstressed group

which was not treated with NHS

the whole-body cortisol level was significantly increased by treatment with NHS (

P

<

0.05). Compared with the NHS-treated stressed control group

pre-treatment with EHDF at concentrations of 5–20 mg/L for 6 min significantly prevented the NHS-increased whole-body cortisol level (

P

<

0.05). In addition

ACTH challenge test showed that EHDF completely blocked the effects of ACTH on cortisol secretion (

P

<

0.05).

Conclusion:

2

EHDF may be a good antistress candidate and its mechanism of action may be related to its positive effects on cortisol release.