Fig 1.
Experimental design and time-dependent changes in the physical and biochemical parameters in restraint stressed rats.
(A) Timeline diagram shows restraint stress induction protocol and behavioral tests. All rats were acclimatized for 1 week prior to 1-, 4-, or 8-week stress induction (black). One- and 4-week groups, were subjected to preceding stress-free period of 7 and 4 weeks (gray), respectively. Behavioral tests, i.e., elevated plus-maze (EPM), elevated T-maze (ETM), novel object recognition (NOR), Morris water maze (MWM), and forced swimming test (FST), were performed at the end of stress session. (B) Baseline body, (C) final body weight, (D) weight gain, (E) daily food intake, (F) dry weight of adrenal gland, and (G) dry adrenal gland weight normalized by body weight (BW) in 1-, 4-, and 8-week restraint stressed rats. (H) Glucocorticoid receptor (GR) protein expression normalized by β-actin in control and 1-week stressed rats. Inset: representative electrophoresis bands of GR and β-actin. (I–J) Serum and urinary corticosterone levels in 4-week stressed rats. Numbers of animals are noted in parentheses. *p < 0.05, **p < 0.01, ***p < 0.001 stress vs. control.
Fig 2.
Time-dependent changes in the stress-induced anxiety-like behaviors in rats as determined by EPM and ETM.
(A) Percent open arm entry, (B) percent open arm time, (C) percent closed arm entry, (D) percent closed arm time, and (E) total number of entries in 1-, 4-, and 8-week stressed male rats, as determined by elevated plus-maze (EPM). (F) One-way escape latency, (G) baseline time, (H) avoidance 1, and (I) avoidance 2 in stressed rats, as determined by elevated T-maze (ETM). Numbers of animals are noted in parentheses. *p < 0.05, **p < 0.01, ***p < 0.001 stress vs. control.
Fig 3.
Time-dependent changes in the stress-induced anxiety-like behaviors in rats as determined by OFT.
(A) Inner zone time, (B) outer zone time, (C) number of lines crossed in the first 30 seconds, and (D) total lines crossed in 1-, 4-, and 8-week stressed male rats, as determined by open field test (OFT). Numbers of animals are noted in parentheses. *p < 0.05 stress vs. control.
Fig 4.
Time-dependent changes in the stress-induced depression-like behaviors and memory impairment in rats.
(A) Swimming duration, (B) climbing duration, and (C) immobility duration in 1-, 4-, and 8-week stressed male rats, as determined by forced swimming test (FST). (D) Escape latency, (E) correct quadrant time, and (F) discrimination ratio in stressed rats, as determined by Morris water maze (MWM) and novel object recognition (NOR) tests. Numbers of animals are noted in parentheses. *p < 0.05, **p < 0.01, ***p < 0.001 stress vs. control.
Fig 5.
Experimental design and the effects of pharmacological treatments and voluntary wheel running on physical and biochemical parameters in stressed rats.
(A) Timeline diagram shows voluntary wheel running and pharmacological treatment protocols. After 1-week acclimatization, rats were divided into one control (vehicle-treated (Veh)/sedentary) and three experimental groups, i.e., agomelatine-treated (Ago), venlafaxine-treated (Vlx), and running (Ex) groups. Drug administration and exercise intervention were given for 4 weeks (pre-treatment), followed by 4-week stress exposure (stress induction), during which rats received neither drug treatment nor exercise intervention. Behavioral tests were performed at the end of stress induction period. (B) Running distance per day in control and stressed groups. Body weight gain and daily food intake, after pre-treatment (C–D, respectively) and after stress induction period (E–F, respectively). (G) Dry adrenal gland weight normalized by BW, (H) dry heart weight, and (I) dry heart weight normalized by body weight (BW) in sedentary and running rats. The control group was stress-free, whereas the stress group was exposed to 4-week restraint stress. (J) Serum corticosterone levels in stressed rats subjected to each treatment. Pre-Ex, pre-exercise period. Numbers of animals are noted in parentheses. *p < 0.05, **p < 0.01, ***p < 0.001 exercise group vs. control (Veh/sedentary) group. †p < 0.05, ††p < 0.01, †††p < 0.001 each experimental group vs. stressed (Veh/sedentary) group. ##p < 0.01 stressed sedentary group vs. sedentary control group.
Fig 6.
Effects of pharmacological treatments and voluntary wheel running on anxiety-like behaviors in stressed rats.
(A) Percent open arm entry, (B) percent open arm time, (C) percent closed arm entry, (D) percent closed arm time, and (E) total arm entries in stressed rats subjected to agomelatine (Ago) or venlafaxine (Vlx) treatment or voluntary wheel running (Ex), as determined by elevated plus-maze (EPM). (F) One-way escape latency, (G) baseline, (H) avoidance 1, and (I) avoidance 2 in stressed rats as determined by elevated T-maze (ETM). Numbers of animals are noted in parentheses. †p < 0.05, †††p < 0.001 compared with vehicle (Veh)-treated group.
Fig 7.
Effects of pharmacological treatments and voluntary wheel running on anxiety-like behaviors in stressed rats.
(A) Inner zone time, (B) outer zone time, (C) number of lines crossed in the first 30 seconds, and (D) total lines crossed in stressed rats subjected to agomelatine (Ago) or venlafaxine (Vlx) treatment or voluntary wheel running (Ex), as determined by open field test (OFT). Numbers of animals are noted in parentheses. *p < 0.05 compared to vehicle (Veh)-treated group.
Fig 8.
Effects of pharmacological treatments and voluntary wheel running on the prevention of depression-like behavior in stressed rats.
(A) Swimming duration, (B) climbing duration, and (C) immobility duration in stressed rats subjected to agomelatine (Ago) or venlafaxine (Vlx) treatment or voluntary wheel running (Ex), as determined by forced swimming test (FST). Numbers of animals are noted in parentheses. ††p < 0.01, †††p < 0.001 compared with vehicle (Veh)-treated group.
Fig 9.
Effects of pharmacological treatments and voluntary wheel running on memory impairment in stressed rats.
(A) Escape latency and (B) correct quadrant time in stressed rats subjected to agomelatine (Ago) or venlafaxine (Vlx) treatment or voluntary wheel running (Ex), as determined by Morris water maze (MWM). (C) Discrimination ratio for novel object recognition (NOR) in stressed rats. Numbers of animals are noted in parentheses. †p < 0.05, ††p < 0.01, †††p < 0.001 compared with vehicle (Veh)-treated group.
Fig 10.
Expression of brain-derived neurotrophic factor (BDNF) in stressed rats pre-treated with drugs and exercise.
Hippocampal BDNF protein expression normalized by β-actin in 4-week stressed rats subjected to agomelatine (Ago) or venlafaxine (Vlx) treatment or voluntary wheel running (Ex) as determined by Western blot analysis. Inset: representative electrophoresis bands of BDNF and β-actin. Numbers of animals are noted in parentheses. †p < 0.05, †††p < 0.001 compared with vehicle (Veh)-treated group.