Study on Ginsenoside Rb1 and Depression

Depression is a mental illness that is currently receiving a lot of attention. Its core symptoms are obvious moodiness, loss of pleasure, and abnormal eating and sleeping habits. It is generally believed to be caused by a combination of biological, genetic, environmental, and psychological factors. According to the World Health Organization, depression has become one of the most burdensome diseases worldwide due to the increasing number of physical or mental disabilities in patients with depression [1]. The resulting stress not only causes suffering for patients and their families, but also has a negative impact on social development from a macro perspective. Currently, clinical treatments for depression usually include medication and psychotherapy. From the perspective of drug therapy, commonly used antidepressants such as monoamine oxidase inhibitors and tricyclic antidepressants generally have disadvantages such as poor patient compliance, a single target, and many adverse reactions [2].

There is a wealth of experience in the treatment of depression with traditional Chinese medicine, as documented in numerous ancient medical texts. Due to the complexity of the chemical composition of traditional Chinese medicine and the diversity of pharmacological targets, combined with the unique theoretical guidance and dialectical thinking of traditional Chinese medicine, the antidepressant effects of natural medicines and traditional Chinese medicine formulas have attracted increasing attention. Ginseng has been known since ancient times in China as the “king of herbs” and is a supreme Chinese herbal medicine with the functions of nourishing yin and replenishing life, strengthening the vital energy and consolidating the foundations. The Shennong Bencao Jing (the Divine Husbandman's Classic of the Materia Medica) states that ginseng “mainly nourishes the five internal organs, calms the mind, settles the soul and spirit, stops palpitations, improves eyesight, and invigorates the mind and intellect”.

Its biological activities include increased vitality, improved stress resistance, anti-ageing properties and immunomodulatory activity. In addition, ginseng has a wide range of neurotrophic and neuroprotective effects, including the prevention of ischaemia/reperfusion injury, Alzheimer's disease and antidepressant effects. Its primary active ingredient is ginsenosides. Many scholars have found through animal models and behavioral experiments that ginsenosides, ginsenosides Rg1, Rb1, Re, Rg3, etc., and their metabolites protopanaxadiol [20(S)-protopanaxadiol] all have certain antidepressant effects. The mechanism of action involves the hypothalamic-pituitary-adrenal (HPA) axis and monoamine neurotransmitter (MA) regulation.

1 The mechanism of action of ginsenosides in the treatment of depression

The causes of depression are currently unclear, and there are many theories about this. Most of the research has focused on the neuroendocrine system, neuroimmune system, neurotransmitter system and neurotrophic substances. These hypotheses are related to dysfunction of the HPA axis, impaired regulation of monoamine neurotransmitters and their receptors, impaired regulation of neuronal plasticity and neuronal regeneration, and increased release of inflammatory factors. It has been reported in the literature that the anti-depressant mechanism of ginsenosides is mainly related to improving the dysregulation of the HPA axis, increasing the levels of brain-derived neurotrophic factor and monoamine neurotransmitters, and reducing the abnormal expression of cytokines (Figure 1).

1.1 By regulating the function of the HPA axis, it increases brain-derived neurotrophic factor

In recent years, a large number of studies have shown that the HPA axis is involved in the pathophysiology of a variety of emotional and cognitive disorders. Neuroendocrine studies have found that the HPA axis is hyperactive in patients with major depression, and there is a certain relationship between the incidence of depression and HPA axis dysfunction [3]. Stress triggers hyperactivity of the HPA axis, which increases the release of glucocorticoids from the adrenal cortex. Some scholars have described and summarized the pharmacological effects of two types of ingredients, ginsenosides and saponins, from the perspective of regulating the HPA axis. Depression is mainly caused by damage to the negative feedback regulatory mechanism of the HPA axis, and nerve cells are damaged by excessive glucocorticoid release [4]. In addition, studies have shown that the plasma brain derived neurotrophic factor (BDNF) levels of depressed patients are decreased, and the BDNF mRNA content of peripheral monocytes in depressed patients with suicidal thoughts is significantly lower than that of normal people. It has also been found that as the severity of depression deepens, the greater the decrease in BDNF mRNA content, confirming that BDNF plays an important role in the pathogenesis of depression [5].

Liu et al. [6] investigated the mechanism of the antidepressant effect of ginsenosides by measuring the levels of corticosterone (CORT), glucocorticoid receptor (GR), mineralocorticoid receptor (MR) and BDNF mRNA in rat serum and brain tissue. The results showed that rats after 6 weeks of chronic unpredictable stress exhibited significantly decreased sucrose preference index and significantly increased immobility time in the forced swimming test (FST), which are depressive behaviors. Subsequent biochemical tests found that the CORT level in the serum of rats with depressive-like behaviors increased, and the mRNA levels of GR in the hippocampus, BDNF in the hippocampus and cerebral cortex were also significantly decreased. In addition, when a depression model was prepared and three doses of ginsenosides (12.5, 25, and 50 mg·kg-1) were given for 6 weeks, it was found that ginsenosides could significantly improve the depressive-like behavior and biochemical changes in rats caused by chronic stress, and the effect became more obvious with increasing dose. This suggests that the mechanism of ginsenoside's antidepressant effect may be related to regulating the function of the HPA axis and increasing BDNF mRNA levels in the hippocampus and cerebral cortex.

1.2 Antidepressant effect by regulating cytokines and changing the number of astrocytes

The activation of the immune system in the context of depression has also received a great deal of attention from researchers. The main feature is an increase in the patient's plasma levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). These abnormally expressed cytokines in the body can activate the downstream signal molecule pathway of nuclear transcription factor-κB (nuclear factor-κB, NF-κB), transmit signals through the blood-brain barrier to the central nervous system, and affect the balance of central neuron activity, thereby accelerating the development of depressive symptoms. Patients with significantly improved depressive symptoms have significantly lower IL-6 levels [7], thus indicating that depression can be treated by reducing cytokine secretion.

Astrocytes (AS) are one of the main components of the central nervous system (CNS) and are closely linked to CNS diseases. They contain neurotrophic factors that have the effect of long-term nutritional support for neurons. In studies of antidepressants, it is often found that their antidepressant effects may be related to mechanisms such as neuroprotection, promotion of neuronal regeneration and protection of astrocytes. Astrocytes, which supply energy in the form of glucose, are involved in glutamate transport and metabolism, regulate the activity of N-methyl-D-aspartate receptors, and adjust imbalances in inflammatory responses. Dysfunction of astrocytes is one of the factors contributing to the development of depression.

An et al. [8] used a neuroinflammatory depression model induced by lipopolysaccharide (LPS) to evaluate the antidepressant effect of ginseng total saponins (GTS). The results showed that the recovery of LPS-induced depressive behavior by GTS was paralleled by a decrease in the levels of IL-1β, IL-6, and TNF-α in the hippocampus of mice with the depressive model. and found that GTS can significantly inhibit the production of various pro-inflammatory factors in mice stimulated by LPS. Chen et al. [9] found through experiments that the administration of GTS can significantly counteract the depression-like behavior caused by administration of corticosterone. High doses of GTS can reverse the decrease in the number of glial fibrillary acidic protein-positive (GFAP+) astrocytes and hippocampal volume induced by corticosterone, and a significant improvement could be detected in the reduction of GFAP+ cell protrusion length and cytoplasmic volume in the GTS-administered group. This demonstrates the antidepressant effect of ginseng from the perspective of structural plasticity of hippocampal astrocytes. 

1.3 Increasing the content of monoamine neurotransmitters in the brain

Mechanism of depression The monoamine neurotransmitter theory of depression involves abnormalities in the function of the dopaminergic and adrenergic nervous systems, which are reflected in a decrease in the release of MA such as serotonin (5-hydroxytryptamine, 5-HT), accompanied by abnormal changes in its related transporters, receptors and enzymes. He et al. [10] used high performance liquid chromatography to measured the levels of blood monoamine neurotransmitters and their metabolites in depression and depression with comorbid anxiety disorders. The results showed that the serum concentrations of norepinephrine and epinephrine in patients with depression were significantly lower than those in the control group. This experiment confirmed the hypothesis that depression is caused by a decrease in monoamine neurotransmitters.

Jiang et al. [11] gave dammarane sapogenin (DS), a ginseng active ingredient, to mice in the chronic unpredictable mild stress (CUMS) model and found that oral administration of DS significantly improved depressive behavior compared to mice in the depression model. Biochemical analysis of brain tissue and serum showed that DS treatment restored the decline in the concentrations of hippocampal neurotransmitters caused by CUMS, including serotonin, dopamine (DA), norepinephrine (NE), and amino butyric acid. This confirmed that ginseng can exert an antidepressant effect by increasing the content of monoamine neurotransmitters in the brain.

2  The active component of ginseng that has antidepressant effects

Ginseng is the root of the plant Panax ginseng C.A. Mey, which belongs to the Araliaceae family. Saponins are considered to be the main active ingredients of ginseng. Ginseng saponins can be divided into protoginseng diol, protoginseng triol and oleanolic acid groups according to their structure. The main protopanaxadiols are Rb1, Rc, Rd, and Rg3; the main protopanaxatriols are Re, Rf, Rg1, Rg2, and Rh1; and the oleanolic acid is Ro. So far, there have been extensive studies on the antidepressant effects and mechanisms of action of ginsenosides and ginsenoside monomers or aglycones.

2.1 Ginseng saponins

In studies of the antidepressant effects of ginsenosides, ginseng saponins have mostly been shown to have antidepressant effects in animal experiments. Chen et al. [12] found that giving GTS to mice for 22 consecutive days, which was induced by subcutaneous injection of corticosterone, relieved the depressive-like behavior of the mice without changing the elevated serum corticosterone levels. In terms of mechanism research, Dang et al. [13] used two classic animal models, the FST and chronic mild stress (CMS), to explore the antidepressant effect of GTS. It was observed that GTS significantly shortened the resting time of mice in the FST, and also reversed the CMS rats' sugar water preference index in a starvation environment, as well as the reduction in locomotor activity and the prolongation of the latency to feed. In addition, GTS almost completely reversed the decrease in the concentration of monoamine neurotransmitters and BDNF expression in the hippocampus induced by CMS, indicating that its antidepressant mechanism may be mediated by increasing the concentration of monoamine neurotransmitters and BDNF expression in the hippocampus.

2.2 Ginseng saponin Rg1

Ginseng saponin Rg1 is a representative component of ginseng that possesses many of the biological activities of ginseng. Huang et al. [14] gave mice different doses of Rg1 and found that all three dose groups significantly reduced immobility time in the FST in the acute stress experiment. After chronic stress, all three doses of Rg1 significantly reduced the immobility time of rats in the FST, increased the percentage of sugar water consumed in the sugar water preference test, and prolonged the sleep time of the animals. Zhu et al. [15] found that ginsenoside Rg1 significantly improved the depressive-like behavior of rats in a depression model after long-term administration, as measured by sucrose preference and forced swimming. It was also found that ginsenoside Rg1 exerts an antidepressant effect by mediating the phosphorylation level of the response element binding protein (CAMP-response element binding protein, CREB) to increase the expression of neurotrophic factors in the prefrontal cortex.

Mou et al. [16] used the mouse CUMS model and the gonadectomy model to further verify and analyze the antidepressant effect of Rg1. The results showed that Rg1 significantly reduced the immobility time of mice in the forced swimming and tail suspension experiments, reduced the serum corticosterone level of mice, increased the serum testosterone level, and the GR protein level in the prefrontal cortex and hippocampus, which confirmed that ginsenoside Rg1 can exhibit antidepressant activity by regulating the HPA and hypothalamic-pituitary-gonadal (HPG) axes. The mechanism by which Rg1 can significantly reduce depressive-like behavior in rats has also been explained as follows: long-term Rg1 treatment can improve the ultrastructure of the gap junctions in astrocytes in the prefrontal cortex, which has a positive effect on the functional activity of gap junctions in the brain, indicating that Rg1 may exert an antidepressant effect by protecting the function of astrocyte gap junctions in the prefrontal cortex [17, 18].

Some scholars used transmission electron microscopy to observe the synapses of neurons in the basolateral amygdala (BLA) and detect synaptic plasticity-related proteins CREB and BDNF. The results suggest that ginsenoside Rg1 may have neuroprotective and antidepressant effects by activating the CREB-BDNF system in the BLA. Its improvement of depressive-like behavior may involve the regulation of the synaptic-related factor miR-134 in the basolateral amygdala [19]. In addition, Fan et al. [20] found that chronic pretreatment with ginsenoside Rg1 can significantly inhibit the activity of inflammatory pathways by reducing the overexpression of pro-inflammatory factors and the activation of microglia and astrocytes, thereby reducing the depressive behavior of rats in the CUMS model.

2.3 Ginseng saponin Rb1

Wang et al. [21] found that in the CUMS depression model, after ginseng saponin Rb1 was administered for 21 consecutive days, the levels of monoamine neurotransmitters such as NE, 5-HT, and DA and their metabolites, 5-hydroxyindoleacetic acid, were significantly upregulated in rats, thereby exerting an antidepressant effect. Liu et al. [22] found that rats subjected to chronic stress showed reduced locomotor activity in the open field test, and that the percentage of sucrose preference and the biochemical detection of hippocampal-amygdala microtubule-associated protein 2 (MAP-2) levels were also lower than those of the control group. However, in rats treated with ginsenoside Rb1, all of the above indicators were lower than the control group, but higher than the model group, indicating that ginsenoside Rb1 may produce an antidepressant effect by affecting the expression of MAP-2 in the hippocampus and amygdala.

Recent studies have shown that in the CUMS combined with LPS-prepared depressive C57BL/6J mouse model, the immobility time of mice treated with Rb1 was significantly shortened in the forced swimming and tail suspension experiments, and there was a significant decrease in serum corticotropin and CORT levels. In addition, high doses of Rb1 successfully reversed the elevated TNF-α inflammatory factor and decreased BDNF expression in the hippocampus of mice in the depression model [23]. Therefore, it is considered that ginsenoside Rb1 may be involved in regulating the HPA axis, inflammatory pathways and BNDF to exert an antidepressant effect.

2.4 Other

pharmacological studies have shown that after rats orally ingest 20(S)-protopanaxadiol [20(S)-PPD], the antidepressant effects produced by the TST, FST and olfactory bulbectomy experiments are comparable to those of fluoxetine. In addition, the 20(S)-PPD-treated olfactory bulbectomy animals had higher levels of MA in the brain compared to the animals that did not receive the drug, does not significantly reduce the oxidative stress capacity of brain tissue in olfactory bulbectomy depression model animals as fluoxetine does, and can inhibit the increase in cortisol concentration in the serum of animals undergoing olfactory bulbectomy surgery, interfering with the normal function of the animal's central nervous system, suggesting that 20(S)-PPD can be used as an alternative component in the development of antidepressant drugs [24].

Ginsenoside Rg3 is the main component of red ginseng, and has neuroprotective, neurotoxic resistance, and antidepressant effects on the central nervous system. Some scholars have found that in the FST and TST, the immobility time of mice given ginsenoside Rg3 was significantly lower than that of the blank control group, and that Rg3 completely reversed the downregulation of the hippocampal BDNF signaling pathway induced by chronic social defeat stress, and that the antidepressant effect of Rg3 could be blocked by BDNF signaling pathway inhibitors.

It can be seen that the antidepressant effect of ginsenoside Rg3 is related to the upregulation of the hippocampal BDNF signaling pathway [25]. From an immunomodulatory perspective, Rg3 has a significant ameliorating effect on LPS-induced depressive-like behavior in mice, improves the metabolic disorders of tryptophan and serotonin in the hippocampus, and simultaneously reduces the levels of pro-inflammatory cytokines and tumor necrosis factor, suggesting that Rg3 can effectively improve depressive-like behavior caused by immune activation [26]. In addition, ginsenoside Re can significantly overcome stress-induced behavioral defects by regulating the central noradrenergic system in rats [27]. Ginsenosides Rg2 and Rg5 can produce an antidepressant-like effect in mice, which is partly mediated by promoting hippocampal BDNF signaling pathways [28,29].

3 Conclusion

Depression is an affective disorder. Even though its incidence has been on the rise in recent years, there is still no consensus on its pathogenesis. The use of biochemical indicators to evaluate the efficacy of antidepressants is not perfect. To date, synthetic drug therapy remains the classic weapon against depression, but antidepressant drugs generally have the problems of taking a long time to take effect, causing relapses easily, and having many adverse reactions. Research from the perspective of traditional Chinese medicine or natural products has provided new ideas for more and more scholars exploring and developing more ideal antidepressants. Ginseng is a traditional Chinese medicine with the effects of tonifying the vital energy, nourishing the spleen and lungs, generating body fluids, calming the mind and improving intelligence. A large number of studies have proven that ginsenosides have significant efficacy in the treatment of depression. Ginsenoside Rg1 is currently the most researched ingredient, and there are various explanations for the mechanism by which it mediates its antidepressant effect. However, there is still room for further exploration of the mechanisms and pathways by which many other active ingredients, such as Re, Rg2 and Rg5, exert their effects, and there is a lack of comparative studies on the efficacy of different ginsenosides.

The non-saponin components of ginseng can also be explored for their antidepressant effects. In addition, a literature review found that in the past decade, there has been a wealth of basic research on the antidepressant activity of individual ginsenosides. On this basis, researchers have begun to turn their attention to preclinical studies of ginseng-related Chinese herbal formulas or drug pairs. For example, a modified Chinese herbal formula PAPZ, which uses ginseng, angelica, polygonatum, and prickly pear as raw materials, has recently been shown to have a therapeutic effect on the corticosterone-induced depression model in mice by increasing BDNF protein expression and enhancing brain antioxidant capacity [30]. Zhu Shuwei et al. [31] proposed the concept of antidepressant pairs in the hope of breaking through the bottleneck of modern research on the complex compatibility rules of traditional Chinese medicine prescriptions. At the same time, it was mentioned that there has been very little research on ginseng-related pairs, such as ginseng-angelica. Given that most current clinical antidepressants target a specific site, the diversity of ginsenoside antidepressant mechanisms highlights a significant advantage. Therefore, with further research into the antidepressant effects of ginsenosides, and based on the research into the efficacy of ginsenoside monomers, attempts can be made to develop new antidepressant-related drugs from traditional Chinese medicine, with the aim of ginseng playing a greater role in the treatment of depression and other related emotional disorders.

References

[ 1]Smith K. Mental health: a world of depression [J]. Nature, 2014, 515: 181.

[2]Zhang F, Qin XM, Du GH, et al. Progress in study of antidepres- sants metabolism in vivo [J]. Acta Pharm Sin, 2017, 52: 1791-1800.

[3]Keller J, Gomez R, Williams G, et al. HPA axis in major depres- sion:  cortisol,  clinical  symptomatology  and  genetic  variation predict cognition [J]. Mol Psychiatry, 2017, 22: 527-536.

[4]Li  H,  Liu  SY,  Wang  B.  Progress  of  the  regulation  effect  of ginsenosides on HPA axis [J]. Acta Pharm Sin, 2014, 49: 569-575.

[5]Lee BH, Kim YK. BDNF mRNA expression of peripheral blood mononuclear cells was decreased in depressive patients who had or had not recently attempted suicide [J]. J Affect Disord, 2010, 125: 369-373.

[6]Liu LQ, Luo Y, Zhang RR, et al. Effects of ginsenosides on hypo- thalamic-pituitary-adrenalfunction andbrain-derivedneurotrophic factor in rats  exposed to  chronic unpredictable mild  stress  [J]. China J Chin Mater Med, 2011, 36: 1342-1347.

[7]Lou JS, Yang XC, Fang J, et al. The mediation of immune activa- tion on serotonin and glutamate systems in pathological process of depression [J]. Chin Pharmacol Bull, 2009, 25: 1555-1558.

[8]An K, Hao H, Xiao Z, et al. Peripheral anti-inflammatory effects explain the ginsenosides paradox between poor brain distribution and  anti-depression  efficacy  [J].  J  Neuroinflammation,  2011, 8: 100.

[9]Chen  L,  Wang X, Lin ZX, et al. Preventive effects of ginseng total   saponins  on  chronic  corticosterone-induced  impairment in  astrocyte  structural  plasticity  and  hippocampal  atrophy  [J]. Phytother Res, 2017, 31 : 1341-1348.

[ 10]He  YC,  Zhang  B,  Zhai  W,  et  al.  Value  of serum  monoamine neurotransmitters and their metabolites in diagnosis of comorbid anxiety and depression and major depressive disorder [J]. J Third Mil Medi Univ, 2014, 36: 806-810.

[ 11]Jiang N,  Zhang  BY, Dong LM, et al. Antidepressant effects of dammarane  sapogenins  in  chronic  unpredictable  mild   stress- induced depressive mice [J]. Phytother Res, 2018, 32: 1023-1029.

[ 12]Chen  L,  Dai  J,  Wang  Z,  et  al.  The  antidepressant  effects  of ginseng  total  saponins  in  male  C57BL/6N  mice  by  enhancing hippocampal inhibitory phosphorylation of GSK-3β [J]. Phytother Res, 2014, 28: 1102-1106.

[ 13]Dang H, Chen Y, Liu X, et al. Antidepressant effects of ginseng total  saponins  in  the  forced  swimming  test  and  chronic  mild stress  models  of  depression   [J].  Prog  Neuropsychopharmacol Biol Psychiatry, 2009, 33: 1417-1424.

[ 14]Huang  Q, Chu  SF, Lian XY, et al. Antidepressive-like effect of ginsenoside Rg1 and its mechanism [J]. Acta Neuropharm, 2013, 3: 1-11.

[ 15]Zhu  X,  Gao  R, Liu Z,  et  al.  Ginsenoside Rg1 reverses  stress- induced  depression-like  behaviours  and  brain-derived  neuro- trophic factor expression within the prefrontal cortex  [J]. Eur J Neurosci, 2016, 44: 1878-1885.

[ 16]Mou  Z, Huang Q, Chu  SF, et al. Antidepressive effects of gin- senoside Rg1 via regulation of HPA and HPG axis  [J]. Biomed Pharmacother, 2017, 92: 962-971.

[ 17]Jin C, Wang ZZ, Zhou H, et al. Ginsenoside Rg1-induced antide- pressant effects involve the protection of astrocyte gap junctions within  the  prefrontal  cortex   [J].  Prog  Neuropsychopharmacol Biol Psychiatry, 2017, 75: 183-191.

[ 18]Ren Q, Xia CY, Wang ZZ, et al. Protective effects of ginsenoside Rg1 against corticosterone-induced primary astrocytes injury [J]. Acta Pharm Sin, 2017, 52: 1410-1415.

[ 19]Yu  H, Fan C, Yang L, et al. Ginsenoside Rg1 prevents chronic stress-induced depression-like behaviors and neuronal structural plasticity in rats [J]. Cell Physiol Biochem, 2018, 48: 2470-2482.

[20]Fan C, Song Q, Wang P, et al. Neuroprotective effects of ginsen- oside-Rg1   against   depression-like  behaviors   via   suppressing glial activation, synaptic deficits, and neuronal apoptosis in rats [J]. Front Immunol, 2018, 9: 2889.

[21]Wang GL, He ZM, Zhu HY, et al. Involvement of serotonergic, noradrenergic and dopaminergic systems in the antidepressant-like effect  of ginsenoside Rb1,  a major  active  ingredient  of Panax ginseng C.A. Meyer [J]. J Ethnopharmacol, 2017, 204: 118-124.

[22]Liu  J, Zang W, Yuan Y, et al. Influence of ginsenoside Rb1 on expression   of  phosphorylated   MAP-2   in   hippocampus   and amygdala of CUMS rat  [J]. J Liaoning Univ Tradit Chin Med, 2016, 18: 47-49.

[23]Lu YY, Zhu  MJ, Ni LN, et al. Establishment of CUMS + LPS induced depression model in mice and antidepressant mechanism research of ginsenoside Rb1  [J]. J Yantai Univ (Nat Sci Engine Edit), 2019, 32: 146-150.

[24]Xu  C, Teng J, Chen W, et al. 20(S)-Protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal  tests  [J].  Prog  Neuropsychopharmacol  Biol  Psychiatry, 2010, 34: 1402-1411.

[25]You Z, Yao Q, Shen J, et al. Antidepressant-like effects of ginsen- oside  Rg3  in  mice  via  activation  of  the  hippocampal  BDNF signaling cascade [J]. J Nat Med, 2017, 71 : 367-379.

[26]Kang A, Xie T, Zhu D,  et al. Suppressive effect of ginsenoside Rg3 against lipopolysaccharide-induced depression-like behavior and neuroinflammation in mice  [J]. J Agric Food Chem, 2017, 65: 6861-6869.

[27]Lee B, Shim I, Lee H, et al. Effect of ginsenoside Re on depression- and anxiety-like behaviors and cognition memory deficit induced by repeated immobilization in rats  [J]. J Microbiol Biotechnol, 2012, 22: 708-720.

[28]Ren Y, Wang  JL, Zhang X, et al. Antidepressant-like effects of ginsenoside Rg2 in a chronic mild stress model of depression [J]. Brain Res Bull, 2017, 134: 211-219.

[29]Xu  D,  Wang  C,  Zhao  W,  et  al.  Antidepressant-like  effects  of ginsenoside  Rg5  in  mice:  involving  of  hippocampus  BDNF signaling pathway [J]. Neurosci Lett, 2017, 645: 97-105.

[30]Chen H, Huang  Q, Zhang  S, et al. The Chinese herbal formula PAPZ  ameliorates behavioral  abnormalities  in  depressive  mice [J]. Nutrients, 2019, 11 : 859.

[31]Zhu SW, Gao XX, Tian JS, et al. Research progress of traditional Chinese antidepressant herb-pair  [J]. Acta Pharm  Sin, 2019, 54: 235-244.