Xiao Yao San Improves Depressive-Like Behaviors in Rats with Chronic Immobilization Stress through Modulation of Locus Coeruleus-Norepinephrine System

Abstract

Most research focuses on the hypothalamic-pituitary-adrenal (HPA) axis, hypothalamus-pituitary-thyroid (HPT) axis, and hypothalamus-pituitary-gonadal (HPGA) axis systems of abnormalities of emotions and behaviors induced by stress, while no studies of Chinese herbal medicine such as Xiao Yao San (XYS) on the mechanisms of locus coeruleus-norepinephrine (LC-NE) system have been reported. Therefore, experiments were carried out to observe mechanism of LC-NE system in response to chronic immobilization stress (CIS) and explore the antidepressant effect of XYS. Rat model was established by CIS. LC morphology in rat was conducted. The serum norepinephrine (NE) concentrations and NE biosynthesis such as tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DBH), and corticotrophin-releasing-factor (CRF) in LC were determined. Results showed that there were no discernible alterations in LC in rats. The serum NE concentrations, positive neurons, mean optical density (MOD), and protein levels of TH, DBH, and CRF in model group were significantly increased compared to the control group. But XYS-treated group displayed a significantly decreased in NE levels and expressions of TH, DBH, and CRF compared to the model group. In conclusion, CIS can activate LC-NE system to release NE and then result in a significant decrease in rats. XYS treatment can effectively improve depressive-like behaviors in rats through inhibition of LC-NE neurons activity.

Figure 1

Effect of XYS on depressive-like behaviors of rats with CIS. (a) Actions and furs were observed in rats with CIS. (b) Rat body weight was recorded once a week during 21 d-CIS period. (c) Sucrose preference test was conducted once a week during 21 d-CIS period. Data were expressed as mean ± SD, n = 12 per group. ^△△ P < 0.01, ^△ P < 0.05 versus control, ^** P < 0.01, ^* P < 0.05 versus model.

Figure 2

Effect of XYS on serum NE of rats with CIS. Data were expressed as mean ± SD, n = 12 per group. ^△ P < 0.01 versus control, ^* P < 0.01 versus model.

Figure 3

LC morphology in rats with CIS (H&E staining). (a) Morphology and site of LC in rat. (b) Morphology of LC in rats after modeling for 21 d CIS among four groups. n = 6 per group.

Figure 4

Effect of XYS on the expressions of TH, DBH, and CRF in LC of rats with CIS. ((a), (b), and (c)) The number of positive cells and mean density (SD) of TH, DBH, and CRF in LC of rats were determined by immunohistochemical staining. Data are expressed as mean ± SD, n = 6 per group. ^* P < 0.05, ^** P < 0.01 versus control, ^△ P < 0.01 versus model. (d) The protein expressions of TH, DBH and CRF in LC of rats were measured by Western blotting. Data were expressed as mean ± SD, n = 6 per group. ^** P < 0.01 versus control, ^△ P < 0.05, ^△△ P < 0.01 versus model.