Polygalasaponin XXXII, a triterpenoid saponin from Polygalae Radix, attenuates scopolamine-induced cognitive impairments in mice

Phytochemical determination and mechanistic investigation of Polygala tenuifolia root (Yuanzhi) extract for bronchitis: UPLC-MS/MS analysis, network pharmacology and in vitro/in vivo evaluation

ETHNOPHARMACOLOGICAL RELEVANCE

Bronchitis is a respiratory disease characterized by a productive cough. Polygala tenuifolia Willd., commonly known as Yuan zhi, is a traditional Chinese herbal medicine used for relieving cough and removing phlegm. Despite its historical use, studies are lacking on the effectiveness of P. tenuifolia in treating bronchitis. Furthermore, the molecular mechanisms underlying the action of its bioactive compounds remain unknown.

AIM OF THE STUDY

This study aims to identify the main bioactive compounds responsible for the effects of P. tenuifolia liquid extract (PLE) in treating bronchitis and to elucidate the associated molecular mechanisms.

MATERIALS AND METHODS

The main chemical compounds in PLE were identified and determined using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The antitussive, expectorant and anti-inflammatory activities of PLE were evaluated in an ammonia-induced mouse cough model, a tracheal phenol red excretion mouse model, and a xylene-induced ear swelling mouse model, respectively. A network pharmacology analysis was conducted to investigate the associated gene targets, gene ontology, and KEGG pathways related to the main bioactives in PLE targeting bronchitis. PLE and its five bioactive compounds were assessed for their potential anti-inflammatory activities in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Western blot analysis was conducted to elucidate the associated molecular mechanisms.

RESULTS

Thirty-seven compounds in PLE were identified, and twelve main compounds were further quantified in PLE using UPLC-MS/MS. PLE oral gavage administrations (0.6 and 0.12 mg/kg) for 7 days markedly reduced cough frequency, prolonged latency period of cough, reduced phlegm and inflammation in mice. The network pharmacology analysis identified 57 gene targets of PLE against bronchitis. The PI3K/AKT and MAPK signalling pathways were the top two modulated pathways. In RAW264.7 cells, PLE (12.5-50 μg/mL) significantly reduced cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α. PLE downregulated LPS-elevated protein targets in both PI3K/AKT and MAPK signaling pathways. In PLE, tenuifolin, polygalaxanthone ⅠⅠⅠ, polygalasaponin ⅩⅩⅤⅢ, tenuifoliside B, and 3,6'-Disinapoyl sucrose, were identified as the top five core components responsible for treating bronchitis. These compounds were also found to modulate the protein targets in the PI3K/AKT and MAPK signalling pathways.

CONCLUSIONS

This study demonstrated the potential therapeutic effects of PLE on bronchitis by reducing cough, phlegm and inflammation. The anti-inflammatory action and molecular mechanisms of the 5 main bioactive compounds in PLE were partly validated through the in vitro assays. The findings provide valuable insights into the mechanisms underlying the traditional use of PLE for bronchitis.

Saponin components in Polygala tenuifolia as potential candidate drugs for treating dementia

Objective

This study aims to elucidate the intervention effects of saponin components from Polygala tenuifolia Willd (Polygalaceae) on dementia, providing experimental evidence and new insights for the research and application of saponins in the field of dementia.

Materials and Methods

This review is based on a search of the PubMed, NCBI, and Google Scholar databases from their inception to 13 May 2024, using terms such as "P. tenuifolia," "P. tenuifolia and saponins," "toxicity," "dementia," "Alzheimer's disease," "Parkinson's disease dementia," and "vascular dementia." The article summarizes the saponin components of P. tenuifolia, including tenuigenin, tenuifolin, polygalasaponins XXXII, and onjisaponin B, as well as the pathophysiological mechanisms of dementia. Importantly, it highlights the potential mechanisms by which the active components of P. tenuifolia prevent and treat diseases and relevant clinical studies.

Results

The saponin components of P. tenuifolia can reduce β-amyloid accumulation, exhibit antioxidant effects, regulate neurotransmitters, improve synaptic function, possess anti-inflammatory properties, inhibit neuronal apoptosis, and modulate autophagy. Therefore, P. tenuifolia may play a role in the prevention and treatment of dementia.

Conclusion

The saponin components of P. tenuifolia have shown certain therapeutic effects on dementia. They can prevent and treat dementia through various mechanisms.

A novel strategy on the study of whole intestinal metabolic profiles for Polygalae Radix before and after processing

INTRODUCTION

Relieving toxicity and enhancing a calming effect after processing Polygalae Radix (PR) are widely known. Aromatic carboxylic acids (ACAs) may be crucial processed products. However, due to the limited detection methods for ACAs, the whole metabolic profiles via intestinal bacteria are still not very clear.

OBJECTIVE

Designing a novel strategy for the detection of ACAs and tracking the whole metabolic profiles before and after processing PR.

MATERIALS AND METHODS

The stable-isotope labelling derivatisation (SILD) method based on multidimensional ultra-high performance liquid chromatography coupled with a mass spectrometer (UHPLC-MS) technology and UNIFI-pathway mode was firstly designed to systematically study the metabolisms of all the drug-derived ingredients ranging from m/z 100 to 2000 in processing PR via intestinal bacteria. Firstly, the SILD with UHPLC coupled with a triple-quadrupole MS technology was designed to trace eight ACA metabolites of the processed PR with intestinal bacteria. Additionally, the UHPLC coupled with a quadrupole time-of-flight MS with UNIFI-pathway mode was adopted to monitor relatively big metabolites.

RESULTS

The metabolism mechanism of ACAs (eight kinds) and the relatively big molecular metabolites (98 kinds) were deeply traced in PR, PR with refined honey (HP), and PR with licorice (LP) via the intestinal bacteria. Totally 106 intact metabolic profiles of drug-derived ingredients were presented. Importantly, the influence of LP on the metabolism of compounds after incubation of intestinal bacteria was greater than that of HP.

CONCLUSION

This research provides a comprehensive and systematic guidance for further study on in vivo metabolisms of the processed PR.

Elucidating the promising role of traditional Chinese medicine in neuroprotection against oxidative stress encompassing Alzheimer's disease

Medicinal plants are being used from time immemorial for their therapeutic benefits and have immense value in the therapy of neurodegenerative disorders. One of the most important neurological disorders is Alzheimer's disease (AD) which is a major contributor to dementia and is accompanied by abundant oxidative stress in the brain tissue. A critical pathway to target the increased oxidative stress is to administer agents with antioxidant potential. Despite currently available clinical treatments to treat AD such as cholinesterase inhibitors or NMDA antagonists which address only the symptoms and cannot hamper disease progression, no efficient available clinical treatment can break the vicious cycle of oxidative stress and neurodegeneration till date. The main objective of presenting this review is that traditional Chinese medicine (TCM) acts as a promising candidate in breaking this vicious cycle and improves the quality of life of the debilitating patients. The active constituents of various herbs in TCM including Angelica sinensis, Radix polygalae, Polygala tenuifolia, and members of the Lamiaceae family have acquired experience of managing oxidative stress as indicated in the review for more than a thousand years now, and the preclinical and clinical evidence of their therapeutic potential has been highlighted in the review. Most importantly, Chinese herbs provide a multiple-target approach rather than a single-target approach and thus can target multiple pathways involved in AD at once. The Chinese herbs can definitely untangle the issues in the current therapy regimen of AD.

Therapeutic potential of Polygala saponins in neurological diseases

BACKGROUND

There are many types of neurological diseases with complex etiologies. At present, most clinical drugs can only relieve symptoms but cannot cure these diseases. Radix Polygalae, a famous traditional Chinese medicine from the root of plants of the genus Polygala, has the traditional effect of treating insomnia, forgetfulness, and palpitation and improving intelligence and other symptoms of neurological diseases. Saponins are important bioactive components of plants of the genus Polygala and exhibit neuroprotective effects.

PURPOSE

This review aimed to summarize the traditional use of Polygala species and discuss the latest phytochemical, pharmacological, and toxicological findings, mainly with regard to Polygala saponins in the treatment of neurological disorders.

METHODS

Literature was searched and collected using databases, including PubMed, Science Direct, CNKI, and Google Scholar. The search terms used included "Polygala", "saponins", "neurological diseases", "Alzheimer's disease", "toxicity", etc., and combinations of these keywords. A total of 1202 papers were retrieved until August 2022, and we included 135 of these papers on traditional uses, phytochemistry, pharmacology, toxicology and other fields.

RESULTS

This literature review mainly reports on the traditional use of the Polygala genus and prescriptions containing Radix Polygalae in neurological diseases. Phytochemical studies have shown that plants of the genus Polygala mainly include saponins, flavonoids, oligosaccharide esters, alkaloids, coumarins, lignans, flavonoids, etc. Among them, saponins are the majority. Modern pharmacological studies have shown that Polygala saponins have neuroprotective effects on a variety of neurological diseases. Its mechanism of action involves autophagic degradation of misfolded proteins, anti-inflammatory, anti-apoptotic, antioxidative stress and so on. Toxicological studies have shown that Polygala saponins trigger gastrointestinal toxicity, and honey processing and glycosyl disruption of Polygala saponins can effectively ameliorate its gastrointestinal side effect.

CONCLUSION

Polygala saponins are the major bioactive components in plants of the genus Polygala that exhibit therapeutic potential in various neurological diseases. This review provides directions for the future study of Polygala saponins and references for the clinical use of prescriptions containing Radix Polygalae for the treatment of neurological diseases.

Floralozone improves cognitive impairment in vascular dementia rats via regulation of TRPM2 and NMDAR signaling pathway

Vascular dementia (VD) is the second largest type of dementia after Alzheimer's disease. At present, the pathogenesis is complex and there is no effective treatment. Floralozone has been shown to reduce atherosclerosis in rats caused by a high-fat diet. However, whether it plays a role in VD remains elusive. In the present study, the protective activities and relevant mechanisms of Floralozone were evaluated in rats with cognitive impairment, which were induced by bilateral occlusion of the common carotid arteries (BCCAO) in rats. Cognitive function, pathological changes and oxidative stress condition in the brains of VD rats were assessed using Neurobehavioral tests, Morris water maze tests, hematoxylin-eosin staining, Neu N staining, TUNEL staining, Golgi staining, Western blot assay and antioxidant assays (MDA, SOD, GSH), respectively. The results indicated that VD model was established successfully and BCCAO caused a decline in spatial learning and memory and hippocampal histopathological abnormalities of rats. Floralozone (50, 100, 150 mg/kg) dose-dependently alleviated the pathological changes, decreased oxidative stress injury, which eventually reduced cognitive impairment in BCCAO rats. The same results were shown in further experiments with neurobehavioral tests. At the molecular biological level, Floralozone decreased the protein level of transient receptor potential melastatin-related 2 (TRPM2) in VD and normal rats, and increased the protein level of NR2B in hippocampus of N-methyl-D-aspartate receptor (NMDAR). Notably, Floralozone could markedly improved learning and memory function of BCCAO rats in Morris water maze (MWM) and improved neuronal cell loss, synaptic structural plasticity. In conclusion, Floralozone has therapeutic potential for VD, increased synaptic structural plasticity and alleviating neuronal cell apoptosis, which may be related to the TRPM2/NMDAR pathway.

Anxiolytic effects, metabolism and plasma pharmacokinetics of 3, 6' -disinapoylsucrose

3,6'-disinapoylsucrose (DISS) is a bioactive oligosaccharide ester derived from Polygalae Radix. This study aims to explore the anxiolytic effects of DISS and further reveal the material basis by establishing the pharmacokinetics of DISS and its metabolites. Behavioral experiments such as the open field test (OFT) and elevated plus maze test (EPM) were performed to evaluate the anxiolytic effects of DISS in mice after oral administration. By UPLC-MS/MS analysis, DISS and its metabolites both in blood and cerebrospinal fluid were identified, and the pharmacokinetics of DISS and its metabolites were characterized in SD rats after oral administration of DISS (100 mg·kg^-1). Oral DISS could increase the time and frequency of mice entering the central area of the field in OFT and open arm in EPM, which indicated DISS has good anxiolytic effects. We also identified DISS and its metabolites (sinapic acid (SA), 3,4,5-trimethoxycinnamic acid (TMCA), methyl-3,4,5-trimethoxycinnamate (TMCA-CH₂), p-Coumaric acid (CA) and p-methoxycinnamic acid (MA)) in rat plasma and cerebrospinal fluid. The pharmacokinetic results showed that DISS was rapidly absorbed after administration and reached its highest concentration at 12 min, SA had the highest exposure level in vivo and was probably the main active form of DISS action, TMCA could maintain at a low concentration for a long time. In brief, we reported the anxiolytic effect of DISS firstly, revealed the cerebrospinal fluid distribution and pharmacokinetics of DISS and its metabolites. Our findings provide the basis for further insight into the mechanisms involved in the anxiolytic effects of DISS.

Polygala saponins inhibit NLRP3 inflammasome-mediated neuroinflammation via SHP-2-Mediated mitophagy

Activation of the NLRP3 inflammasome and its mediated neuroinflammation are implicated in neurodegenerative diseases, while mitophagy negatively regulates NLRP3 inflammasome activation. SHP-2, a protein-tyrosine phosphatase, is critical for NLRP3 inflammasome regulation and inflammatory responses. In this study, we investigated whether triterpenoid saponins in Radix Polygalae inhibit the NLRP3 inflammasome via mitophagy induction. First, we isolated the active fraction (polygala saponins (PSS)) and identified 17 saponins by ultra-performance liquid chromatography coupled with diode-array detection and tandem quadrupole time-of-flight mass spectrometry (UHPLC-DAD-Q/TOF-MS). In microglial BV-2 cells, PSS induced mitophagy as evidenced by increased co-localization of LC3 and mitochondria, as well as an increased number of autophagic vacuoles surrounding the mitochondria. Furthermore, the mechanistic study found that PSS activated the AMPK/mTOR and PINK1/parkin signaling pathways via the upregulation of SHP-2. In Aβ(1-42)-, A53T-α-synuclein-, or Q74-induced BV-2 cells, PSS significantly inhibited NLRP3 inflammasome activation, which was attenuated by bafilomycin A1 (an autophagy inhibitor) and SHP099 (an SHP-2 inhibitor). In addition, the co-localization of LC3 and ASC revealed that PSS promoted the autophagic degradation of the NLRP3 inflammasome. Moreover, PSS decreased apoptosis in conditioned medium-induced PC-12 cells. In APP/PS1 mice, PSS improved cognitive function, ameliorated Aβ pathology, and inhibited neuronal death. Collectively, the present study, for the first time, shows that PSS inhibit the NLRP3 inflammasome via SHP-2-mediated mitophagy in vitro and in vivo, which strongly suggests the therapeutic potential of PSS in various neurodegenerative diseases.

A comprehensive review on medicinal herbs and novel formulations for the prevention of Alzheimer's disease

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases reported in the aging population across the globe. About 46.8 million people are reported to have dementia, and AD is mainly responsible for dementia in aged people. Alzheimer's disease (AD) is thought to occur due to the accumulation of β-amyloid (Aβ) in the neocortex portion of the brain, nitric oxide mediated dysfunctioning of blood-brain barrier, reduced activity of serine racemase enzyme, cell cycle disturbances, damage of N-methyl-D-aspartate (NMDA) receptors and glutamatergic neurotransmission. Modern treatment methods target the pathways responsible for the disease. To date, solely symptomatic treatments exist for this disease, all making an attempt to counterbalance the neurotransmitter disturbance. Treatments able to prevent or at least effectively modifying the course of AD, referred to as 'disease-modifying' drugs, are still under extensive research. Effective treatments entail a better indulgence of the herbal bioactives by novel drug delivery systems. The herbal bioactive administered by novel drug delivery systems have proved beneficial in treating this disease. This review provides detailed information about the role of medicinal plants and their formulations in treating Alzheimer disease which will be highly beneficial for the researchers working in this area.

Core prescription pattern of Chinese herbal medicine for depressive disorders in Taiwan: a nationwide population-based study

Background

Depressive disorders (DD) affect not only mood and behavior but also various physical functions. Traditional Chinese medicine (TCM) has been shown to have some benefits in treating DD. However, one formula or one single herb might be not show high efficacy when used to treat depression. Thus, this study aimed to examine the core prescription pattern of Chinese herbal medicine (CHM) among patients with DD in Taiwan as a reference for related research and clinical applications.

Methods

All patients, who had been diagnosed with major depressive disorder or minor depression or dysthymia without any other baseline diseases and had at least one CHM outpatient clinical visit from 2002 to 2011, were extracted from three randomly sampled cohorts, namely the 2000, 2005 and 2010 cohorts of the National Health Insurance Research Database (NHIRD) of Taiwan. The collected data was analyzed to explore the patterns of herbal products.

Results

There were 197,146 patients with a diagnosis of DD and of these 1806 subjects had only a diagnosis of DD and utilized CHM. The most common formula was Gan-Mai-Da-Zao-Tang (12.19%), while Suan-Zao-Ren (3.99%) was the most commonly prescribed single herb. The core pattern of prescriptions consisted of a combination of Gan-Mai-Da-Zao-Tang, Jia-Wei-Xiao-Yao-San, Chai-Hu-Jia-Long-Gu-Mu-Li-Tang, He-Huan-Pi, Yuan-Zhi and Shi-Chang-Pu.

Conclusions

This study describes the CHM core prescription pattern used to treat patients in Taiwan with DD and it is a potential candidate for study in future pharmacological or clinical trials targeting DD.

Polygala tenuifolia: a source for anti-Alzheimer's disease drugs

Context: Alzheimer's disease (AD) is a chronic neurodegenerative disease that originates from central nervous system lesions or recessions. Current estimates suggest that this disease affects over 35 million people worldwide. However, lacking effective drugs is the biggest handicap in treating AD. In traditional Chinese medicine (TCM), Polygala tenuifolia Willd. (Polygalaceae) is generally used to treat insomnia, memory dysfunction and neurasthenia.Objective: This review article explores the role of P. tenuifolia and its active components in anti-Alzheimer's disease.Methods: Literature for the last ten years was obtained through a search on PubMed, SciFinder, CNKI, Google Scholar, Web of Science, Science Direct and China Knowledge Resource Integrated with the following keywords: Polygala tenuifolia, polygalasaponin XXXII (PGS 32), tenuifolin, polygalacic acid, senegenin, tenuigenin, Alzheimer's disease.Results: Polygala tenuifolia and its active components have multiplex neuroprotective potential associated with AD, such as anti-Aβ aggregation, anti-Tau protein, anti-inflammation, antioxidant, anti-neuronal apoptosis, enhancing central cholinergic system and promote neuronal proliferation.Conclusions: Polygala tenuifolia and its active components exhibit multiple neuroprotective effects. Hence, P. tenuifolia is a potential drug against Alzheimer's disease, especially in terms of prevention.

Combination of acupuncture and Chinese herbal formula for elderly adults with mild cognitive impairment: protocol for a randomized controlled trial

Background

Mild cognitive impairment (MCI) is known as a transitional status between normal cognitive function and Alzheimer’s disease (AD). Acupuncture and Chinese herbal medicines (CHMs) are considered to be beneficial to patients with cognitive impairment. However, it is still unknown whether the combination of the two therapies could optimize the therapeutic effect for MCI. This trial is aimed to evaluate the therapeutic effects of acupuncture and the herbal formula Yishen Granule (YSG) for elderly patients with MCI.

Methods/design

This is a multi-sited, patient-blinded, randomized controlled trial (RCT). Two hundred and forty eligible patients will be randomly divided into four groups: A. acupuncture with YSG, B. acupuncture with placebo herbal medicine, C. sham acupuncture with YSG or D. sham acupuncture with placebo herbal medicine. Acupuncture treatment will be given twice a week for 8 weeks and then once a week for 4 weeks. The herbal treatment patients will be given granules daily for 12 weeks, 8 weeks of standard-dose followed by 4 weeks of mid-dose. The primary outcome is scored by the Montreal Cognitive Assessment (MoCA). The secondary outcomes will be scored by the Mini-Mental State Examination (MMSE) and event-related potential (ERP). All the assessments will be conducted at baseline, and at the eighth and 12th week after intervention starts. The follow-up assessments will be performed with the MoCA in the 12th, 24th, and 36th weeks after intervention ends. Intention-to-treat (ITT) analysis will be used in this RCT.

Discussion

This RCT will provide us information on the effect of treating MCI patients with only acupuncture, herbal formula as well as the combination of both. The additive effect or synergistic effect of acupuncture and Chinese herbal formula will then be analyzed.

Trial registration

This trial is registered with ChiCTR-INR-17011569 on 5 June 2017, and has been approved by the Ethics Committee of Shanghai Municipal Hospital of Traditional Chinese Medicine (2017SHL-KY-05).

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3212-z) contains supplementary material, which is available to authorized users.

Ethanol Extract of Oldenlandia diffusa Herba Attenuates Scopolamine-Induced Cognitive Impairments in Mice via Activation of BDNF, P-CREB and Inhibition of Acetylcholinesterase

Though Oldenlandia diffusa Herba (ODH) has been known to exhibit anti-cancer and anti-inflammatory effects, its anti-amnestic effect has never been reported so far. The aim of this present study was to elucidate the anti-amnestic effect of ODH. ODH pretreatment significantly reduced escape latency of scopolamine treated Institute of Cancer Research (ICR) mice compared to untreated control groups in a Morris water maze test. Similarly, the passive avoidance test showed that ODH treatment recovered the scopolamine induced amnesia in the ICR mouse model. Concentration of Ach in brains of ODH treated mice was increased compared to that of scopolamine treated mice. In addition, activity of acetylcholinesterase (AChE) was notably decreased by ODH. The protein expression of brain-derived neurotrophic factor (BDNF) and phospho-cAMP response element-binding protein (p-CREB) (Ser133) was increased in ODH pretreated group compared to control group. Consistently, immunohistochemistry (IHC) revealed the elevated expression of brain-derived neurotrophic factor (BDNF) and p-CREB in brains of ODH treated mice compared to the control group. Overall, these findings suggest that ODH has anti-amnestic potential via activation of BDNF and p-CREB and inhibition of AChE in mice with scopolamine induced amnesia.

Vitamin B6 prevents isocarbophos-induced vascular dementia in rats through N-methyl-D-aspartate receptor signaling

BACKGROUND

We have previously reported that the long-term exposure of organophosphorus induces vascular dementia (VD) in rats. As a coenzyme, vitamin B6 is mainly involved in the regulation of metabolisms. Whether vitamin B6 improves VD remains unknown.

METHODS

The model of VD was induced by feeding rats with isocarbophos (0.5 mg/kg per two day, 12 weeks). The blood flow of the posterior cerebral artery (PCA) in rat was assessed by transcranial Doppler (TCD). The learning and memory were evaluated by the Morris Water Maze (MWM) test.

RESULTS

Administration of vitamin B6 increased the blood flow in the right and left posterior cerebral arteries and improved the functions of learning and memory in isocarbophos-treated rats. Vitamin B6 increased the protein levels of N-methyl-D-aspartate receptor (NMDAR) 2B, postsynaptic densities (PSDs) protein 95, and calmodulin-dependent protein kinase II (CaMK-II) in the hippocampus, which were decreased by isocarbophos in rats. Morphological analysis by light microscope and electronic microscope indicated disruptions of the hippocampus caused by isocarbophos were normalized by vitamin B6. Importantly, the antagonist of NMDAR signaling by eliprodil abolished these beneficial effects produced by vitamin B6 on PCA blood flow, learning, memory, and hippocampus structure in rats, as well as the protein expression of NMDAR 2B, PSDs protein 95, and CaMK-II in the hippocampus.

CONCLUSION

Vitamin B6 activates NMDAR signaling to prevent isocarbophos-induced VD in rats.

Reduced Consolidation, Reinstatement, and Renewal of Conditioned Fear Memory by Repetitive Treatment of Radix Polygalae in Mice

The therapeutic goal for the treatment of posttraumatic stress disorder (PTSD) is to promote extinction and to prevent the relapse of fearful memories. Research has identified pharmacological treatments that may regulate the formation and extinction of fear memories, but not many reagents that block the relapse of extinguished fear are known. Radix Polygalae (RP) is an Asian herb used for sedation, and its ingredients have anxiolytic and antidepressant properties. As various neurological effects have been identified, we tested whether RP affects the relapse of fear. Freezing in response to a conditioned context and cues was used to measure the effects of RP in mice. In cohort 1 (n = 30), consolidation, extinction, and reinstatement were tested during the course of 18 days of treatment. In cohort 2 (n = 30), consolidation, extinction, and renewal were tested during 10 days of treatment. The consolidation, extinction, reinstatement, and possibly the renewal of context-induced freezing were inhibited due to the administration of RP in animal subjects. However, the effects of RP on the freezing responses of subjects elicited by conditioned auditory cues were less obvious. Because it effectively suppresses the consolidation of fear memories, RP may be used for primary and secondary prevention of symptoms in PTSD patients. Additionally, because it effectively suppresses the reinstatement and renewal of fear memories, RP may be applied for the prevention of fear relapse in PTSD patients who have undergone exposure therapy.