1 - Neurotransmitters:
Depression has been linked to problems or imbalances in the brain with regard to the neurotransmitters serotonin, norepinephrine, and dopamine. [...] What we do know is that antidepressant medications (used to treat the symptoms of depression) are known to act upon these particular neurotransmitters and their receptors.
https://www.mentalhe...rotransmitters/
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The discovery of Yuanzhi-1, a triterpenoid saponin derived from the traditional Chinese medicine, has antidepressant-like activity.
Yuanzhi, the dried root of Polygala tenuifolia Willd., is a well-known traditional Chinese medicine used for its sedative, antipsychotic, cognitive improving, neuroprotective, and antidepressant effects. Yuanzhi-1 (1 nM) had a high affinity for serotonin, norepinephrine and dopamine transporters. Acute toxicity tests indicated that the LD50 of Yuanzhi-1 (86.5mg/kg) was similar to that of duloxetine (73.2 mg/kg). These findings demonstrate that Yuanzhi-1 has a potential to be a novel triple monoamine reuptake inhibitor of antidepressant-like activity.
http://www.ncbi.nlm....pubmed/24614095
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Monoamine oxidase inhibitors (MAOIs) are chemicals which inhibit the activity of themonoamine oxidase enzyme family. They have a long history of use as medications prescribed for the treatment of depression. They are particularly effective in treating atypical depression.[1]
https://en.wikipedia...idase_inhibitor
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Possible mechanism of the antidepressant effect of 3,6'-disinapoyl sucrose from Polygala tenuifolia Willd.
DISS significantly inhibited MAO-A and MAO-B activity and blocked plasma elevated cortisol level, an indicator of the hypothalamic-pituitary-adrenal (HPA) axis. In addition, DISS increases SOD activity, inhibits lipid peroxidation, and lessens production of MDA.
CONCLUSION:
These results suggest that DISS may possess potent and rapid antidepressant properties, which are mediated via MAO, the HPA axis and oxidative systems. These antidepressant actions make DISS a potentially valuable drug for the treatment of depression.
http://www.ncbi.nlm....pubmed/21585386
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2 - NGF, BDNF and the hippocampus:
Nerve growth factor (NGF) has novel antidepressant-like properties in rats.
NGF has antidepressant-like effects but does not appear to have biochemical actions typical of other antidepressants.
http://www.ncbi.nlm....pubmed/19945476
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Exposure to stress and the stress hormone corticosterone has been shown to decrease the expression of BDNF in rats, and, if exposure is persistent, this leads to an eventual atrophy of the hippocampus. Atrophy of the hippocampus and other limbic structures has been shown to take place in humans suffering from chronic depression.[68] In addition, rats bred to be heterozygous for BDNF, therefore reducing its expression, have been observed to exhibit similar hippocampal atrophy. This suggests that an etiological link between the development of depression and BDNF exists. Supporting this, the excitatory neurotransmitter glutamate, voluntary exercise,[69] caloric restriction, intellectual stimulation, curcumin[70] and various treatments for depression (such as antidepressants[71] and electroconvulsive therapy[72]) increase expression of BDNF in the brain. In the case of some treatments such as drugs[73] and electroconvulsive therapy[74] this has been shown to protect against or reverse this atrophy.[73]
https://en.wikipedia...ctor#Depression
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Induction of NGF synthesis in astrocytes by onjisaponins of Polygala tenuifolia, constituents of kampo (Japanese herbal) medicine, Ninjin-yoei-to.
Onjisaponins A, B, E, F and G as major saponins of the root of P. tenuifolia strongly increased the NGF level.
http://www.ncbi.nlm....pubmed/12725562
Enhancements of choline acetyltransferase activity and nerve growth factor secretion by Polygalae radix-extract containing active ingredients in Kami-untan-to.
These results suggest that Polygala radix1 has an important role on the enhancing effects of KUT on ChAT activity and NGF secretion.
http://www.ncbi.nlm....pubmed/23195476
1 Radix Polygalae (the root of Polygala tenuifolia)
Neuroprotective effects of 3,6'-disinapoyl sucrose through increased BDNF levels and CREB phosphorylation via the CaMKII and ERK1/2 pathway.
3,6'-Disinapoyl sucrose (DISS) is an oligosaccharide ester natural product originating from the root of wild Polygala tenuifolia. [...] The results from the present study suggest that DISS-mediated regulation of BDNF gene expression is associated with CREB-mediated transcription of BDNF and upstream activation of ERK1/2 and CaMKII. Finally, DISS may exert neuroprotective and antidepressant effects through these signaling pathways in neuronal cells.
http://www.ncbi.nlm....pubmed/24488601
Effect of Tenuifoliside A isolated from Polygala tenuifolia on the ERK and PI3K pathways in C6 glioma cells.
TFSA increased levels of phospho-ERK and phospho-Akt, enhanced release of BDNF, which were blocked by ERK and PI3K inhibitors, respectively (U0126 and LY294002).
http://www.ncbi.nlm....pubmed/24877714
Tenuigenin promotes proliferation and differentiation of hippocampal neural stem cells.
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Major depressive disorder (MDD) is a common, recurrent mental illness that affects millions of people worldwide. Accumulating evidence suggests that the N-methyl-D-aspartate (NMDA) receptor, a subtype of glutamate receptors, plays an important role in the neurobiology and treatment of this disease. Currently, the non-competitive NMDA receptor antagonist ketamine is considered as one of the most attractive candidate drugs in therapy of treatment-resistant depression. A recent study demonstrated ketamine's rapid antidepressant activity in patients with treatment-resistant MDD and bipolar disorder.
http://www.ncbi.nlm....pubmed/24410564
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Preclinical evidence of rapid-onset antidepressant-like effect in Radix Polygalae extract.
Radix Polygalae (the root of Polygala tenuifolia) is a herb widely used in traditional Asian medicine that is thought to exert a variety of neuropsychiatric effects. Radix Polygalae extract can protect against N-methyl D-aspartate (NMDA) neurotoxicity and induce brain-derived neurotrophic factor (BDNF) expression, suggesting modulatory roles at glutamatergic synapses and possible antidepressant action. In accordance with this hypothesis, Radix Polygalae extract demonstrated antidepressant-like effects in 8-week-old male C57Bl/6 mice by decreasing behavioral despair in the forced swim and tail suspension tasks and increasing hedonic-like behavior in the female urine sniffing test 30 minutes after a single oral administration of 0.1 mg/kg. Reduced latency to acquire a food pellet in the novely suppressed feeding paradigm, without change in anxiety-like behaviors suggested a rapid-onset nature of the antidepressant-like effect. In addition, it decreased the number of failed escapes in the learned helplessness paradigm after two oral administrations 24 hours and 30 minutes before the first test. Finally, it reversed anhedonia as measured by saccharin preference in mice exposed to the chronic stress model after two administrations of 0.1 mg/kg, in contrast to the repeated administration generally needed for similar effect by monoamergic antidepressants. Immobility reduction in tail suspension task was blocked by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist NBQX, a pattern previously demonstrated by ketamine and other ketamine-like rapid-onset antidepressants. Also similarly to ketamine, Radix Polygalae appeared to acutely decrease phosphorylation of GluR1 serine-845 in the hippocampus while leaving the phosphorylation of hippocampal mTOR serine 2448 unchanged. These findings serve as preclinical evidence that Radix Polygalae extract exerts rapid-onset antidepressant effects by modulating glutamatergic synapses in critical brain circuits of depression and may be worthy of further evaluation as a safe substitute to other rapid-onset antidepressants known to have unacceptable side effects.
0.1mg/kg of the root has been noted to have potency comparable to 10mg/kg IV ketamine in mice.
http://www.ncbi.nlm....pubmed/24520403
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Edited by William Sterog, 27 March 2016 - 08:44 AM.