Effects of Camellia Sinensis Extract on Repeated Restraint Stress-Induced Ovariectomized Female Rats

Abstract

The mortality of individuals suffering from depression has been increasing, noticeably of postmenopausal women; consequently, their care and treatment are significant to retain a high quality of life. The aim of this study was to examine the effect of Camellia sinensis (CS) on repeated stress-induced changes of the depression related function on the tail suspension test (TST), forced swimming test (FST) in ovariectomized female rats. After behavioral test, we evaluated the changes in the neurotransmitter by measuring the level of dopamine in the nucleus accumbens (NaC) and the serum levels of estrogen and oxytocin. We used 18F-2-fluoro-deoxy-D-glucose positron emission tomography (18F-FDG-PET) to examine the effects of CS on glucose metabolism in ovariectomized rats. Female rats were randomly segregated into three groups. Nor group was considered as nonoperated and nonstressed group, while the control was the ovariectomized and stressed group (OVX+ST), and CS was the ovariectomized, stressed and CS treated group. The rats were exposed to immobilization stress (IMO) for 14 d (2 h/d), and CS (300 mg/kg, i.p.) was treated 30 min before IMO stress. Significant reduction of immobility in the TST and FST was indicated in rats treatment with CS compared to the control group (OVX+ST). The levels of estrogen in the serum of the Nor and CS groups were significantly elevated compared to the OVX+ST group. Also, CS activated brain glucose metabolism in the cortex. The present findings suggested that CS had antidepressant effectiveness in a menopausal depression animal model. These findings suggest evidence that CS plays a crucial role in stressful situation, providing that CS might be a dependable antidepressant medicine to treat menopausal depression.

Figure 1

Experimental schedule of OVX-induced depression-like behaviors and treatment with CS in rats.

Figure 2

HPLC chromatogram of the ethanol-soluble extract of high temperature processed-green tea extract (HTP). Peaks 1: caffeine, 2: (−)-epigallocatechin 3-O-gallate, 3: (−)-gallocatechin 3-O-gallate, and 4: (−)-epicatechin 3-O-gallate, 5: (+)-catechin 3-O-gallate.

Figure 3

Effects of CS to reduce spent immobility time in the TST and FST. (a) Effect of CS treatment on immobility time in the tail suspension test after restraint stress for 14 consecutive days. (b) Effect of CS treatment on immobility time in the forced swimming test after restraint stress for 14 consecutive days. The data were represented as mean ± standard errors of the mean (SEM). Statistical analysis was conducted using a one-way analysis of variance, followed by post hoc Tukey's test where appropriate, ∗∗∗, P<0.001; ∗∗, P<0.01 vs. Nor group, #, P<0.05; ###, P<0.001 vs. OVX+ST group.

Figure 4

Effects of CS on the alteration of the dopamine level in the NaC. The data were expressed as mean ± standard errors of the mean (SEM). Statistical analysis was conducted using a one-way analysis of variance, followed by post hoc Tukey's test where appropriate, ∗p<0.01 vs. Nor group.

Figure 5

Effect of CS on immobilization-induced change of estrogen and oxytocin concentrations in the serum. The data were expressed as mean ± standard errors of the mean (SEM). Statistical analysis was conducted using a one-way analysis of variance, followed by post hoc Tukey's test where appropriate, #p<0.05 vs. OVX+ST group.

Figure 6

CS changes glucose uptake in the brain. Voxel-wise comparisons between Nor and OVX+ST datasets, (a) OVX+ST and (b) OVX+ST+ CS.