Yokukansan Increases 5-HT1A Receptors in the Prefrontal Cortex and Enhances 5-HT1A Receptor Agonist-Induced Behavioral Responses in Socially Isolated Mice

Traditional uses, chemical compounds, pharmacological activities and clinical studies on the traditional Chinese prescription Yi-Gan San

ETHNOPHARMACOLOGICAL RELEVANCE

A widely used traditional prescription, Yi-Gan San (YGS) is a remedy for neurodegenerative disorders. The formulation consists of seven Chinese medicinal materials in specific proportions, namely Uncariae Ramulus cum Uncis (Uncaria rhynchophylla (Miq.) Miq. ex Havil.), Bupleuri Radix (Bupleurum chinense DC.), Angelicae Sinensis Radix (Angelica sinensis (Oliv.) Diels), Chuanxiong Rhizoma (Ligusticum wallichii Franch.), Poria (Poria cocos (Schw.) Wolf), Atractylodis Macrocephalae Rhizoma (Atractylodes macrocephala Koidz.) and Glycyrrhizae Radix et Rhizoma (Glycyrrhiza uralensis Fisch.). Using YGS has been shown to alleviate various behavioural and psychological symptoms of dementia (BPSD).

AIM OF THIS REVIEW

The goal of this review is to give up-to-date information about the traditional uses, chemistry, pharmacology and clinical efficacy of YGS based on the scientific literature and to learn the current focus and provide references in the next step.

MATERIALS AND METHODS

The database search room was accessed using the search terms "Yi-Gan San" and "Yokukansan" to obtain results from resources such as Web of Science, PubMed, Google Scholar and Sci Finder Scholar. We not only consulted the literature of fellow authors for this review but also explored classical medical books.

RESULTS

YGS has been used to cure neurosis, sleeplessness, night weeping and restlessness in infants. Its chemical components primarily consist of triterpenes, flavonoids, phenolics, lactones, alkaloids and other types of compounds. These active ingredients displayed diverse pharmacological activities to ameliorate BPSD by regulating serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmission. In addition, YGS showed neuroprotective, antistress, and anti-inflammatory effects. The majority of cases of neurodegenerative disorders are treated with YGS, including Alzheimer's disease and dementia with Lewy bodies.

CONCLUSIONS

Based on previous studies, YGS has been used as a traditional prescription in East Asia, such as Japan, Korea and China, and it has diverse chemical compounds and multiple pharmacological activities. Nevertheless, few experimental studies have focused on chemical and quantitative YGS studies, suggesting that further comprehensive research on its chemicals and quality assessments is critical for future evaluations of drug efficacy.

The 2018 Japan Floods Increased the Frequency of Yokukansan Prescriptions Among Elderly: A Retrospective Cohort Study

Objective

The impact of the 2018 Japan Floods on prescriptions of Yokukansan was evaluated.

Methods

This was a retrospective cohort study based on the National Database of Health Insurance Claims which covers all the prescriptions issued in Japan. Participants were patients aged 65 or older who received any medical care at medical institutions located in the three most-severely affected prefectures between 1 year before and after the disaster. We analyzed the number of new prescriptions of Yokukansan and other Kampo drugs among those who had not been prescribed any Kampo for 1 year before the disaster. Kaplan-Meier analysis and a Cox proportional hazards model were used to evaluate the risk of the disaster for a new prescription.

Results

Subjects comprised 1,372,417 people (including 12,787 victims, 0.93%). The hazard ratio (HR) of the disaster for Yokukansan prescriptions was 1.49 [95% confidence intervals (CI): 1.25–1.78], and 1.54 (95% CI: 1.29–1.84) in the crude and age-sex adjusted model, respectively. The HR of the disaster for prescription of other Kampo drugs in the crude and adjusted model was 1.33 (95% CI: 1.27–1.39), and 1.32 (95% CI: 1.27–1.38), respectively. The magnitude of increase of victims prescribed Yokukansan (31.4%) was statistically higher than for those prescribed other Kampo drugs (19.3%) (p < 0.001).

Conclusion

The disaster increased prescriptions of both Yokukansan and other Kampo drugs among elderly victims. The increase was more remarkable in Yokukansan than other Kampo drugs. Clinicians and policymakers should be aware of the increased need for Yokukansan in times of natural disaster.

Characteristics and course of patients treated with Kampo Medicine in the Department of General Medicine

BACKGROUND

A recent investigation reported that 92.7% Japanese family physicians have prescribed Kampo medicine (KM). KM can treat a wide variety of conditions from mental disorders to physical weaknesses. However, the characteristics and course of patients treated with KM at the Department of General Medicine remain unclear.

AIMS

To investigate the characteristics and course of patients treated with KM in our hospital.

METHODS

Data on medical history, complaints, course after Kampo treatment, and Hamilton Depression Rating Scale (HAM-D) scores were retrogradely collected. The background of patients who received Kampo treatment was compared to that of patients who did not.

RESULT

Of 362 patients, 51 were treated with KM. Symptoms for which KM was prescribed included pain, general malaise, or sensory disturbance of extremities. All patients treated with KM were screened and initially diagnosed with a functional disorder or noncritical condition. KM including a crude drug of saiko such as hochuekkito, shigyakusan, shosaikoto, and yokukansan, was frequently prescribed for patients. Subjective symptoms showed improvement (53%) and no change (47%), while worsening was not observed in any patient. HAM-D scores showed that patients treated with KM had higher anxiety levels and related symptoms as well as a higher frequency of mental disorders prior to presenting at the hospital.

CONCLUSION

Most complaints of the patients treated with KM were pain, general malaise, and sensory disturbance. KM is more likely to be prescribed in patients with health-related anxiety or a history of mental disorders.

Comparison of the Effects of Yokukansan and Yokukansankachimpihange on Glutamate Uptake by Cultured Astrocytes and Glutamate-Induced Excitotoxicity in Cultured PC12 Cells

The traditional Japanese Kampo medicine yokukansan (YKS) is effective for behavioral and psychological symptoms of dementia (BPSD) in patients with Alzheimer's disease. As the pharmacological mechanisms, YKS is known to protect astrocytes from thiamine-deficiency (TD)-induced decreased glutamate (Glu) uptake and neuron model cells (PC 12 cells) from Glu-induced death. Yokukansankachimpihange (YKSCH) is an alternative formula to YKS, in which Citrus unshiu peel and Pinellia tuber are added to the YKS components, and is sometimes used to treat BPSD, but its pharmacological properties remain unknown. This study aims to investigate the cellular pharmacological effects of YKS and YKSCH on glutamatergic pathways, compare their efficacy, and determine the differences and similarities in the activities between these formulations. First, we examined the effects of YKS and YKSCH on Glu uptake by cultured astrocytes under TD conditions. We observed significant ameliorative effects of YKS and YKSCH on the TD-induced decrease in Glu uptake, with a 50% effective dose of 8.9 ± 1.8 μg/mL and 45.3 ± 9.2 μg/mL, respectively. Second, using cultured PC12 cells as a model for neurons, we examined the effects of YKS and YKSCH on Glu-induced cell death. We observed that YKS and YKSCH had significant inhibitory effects on Glu-induced cell death, with a 30% effective dose of 51.4 ± 20.8 μg/mL and 49.2 ± 11.0 μg/mL, respectively. Thus, while YKSCH was less effective than YKS in ameliorating the TD-induced decrease in Glu uptake by astrocytes, the two drugs showed similar inhibitory effects on Glu-induced PC12 cell death. These findings are important for understanding the differences and similarities in pharmacological actions between these drugs.

Traditional Oriental Medicines and Alzheimer's Disease

Alzheimer’s disease (AD), which is the most major cause of dementia, is a progressive neurodegenerative disease that affects cognitive functions. Even though the prevalence of AD is continuously increasing, few drugs including cholinesterase inhibitors and N-methyl D-aspartate-receptor antagonists were approved to treat AD. Because the clinical trials of AD drugs with single targets, such as β-amyloid and tau, have failed, the development of multi-target drugs that ameliorate many of the symptoms of AD is needed. Thus, recent studies have investigated the effects and underlying mechanisms of herbal formulae consisting of various herb combinations used to treat AD. This review discusses the results of clinical and nonclinical studies of the therapeutic efficacy in AD and underlying mechanisms of the herbal formulae of traditional Oriental medicines and bioactive compounds of medicinal plants.

Analyses of the possible anti-tumor effect of yokukansan

The Kampo medicine yokukansan (YKS) has a wide variety of properties such as anxiolytic, anti-inflammatory and analgesic effects, and is also thought to regulate tumor suppression. In this study, we investigated the anti-tumor effect of YKS. We used Lewis lung carcinoma (LLC)-bearing mice that were fed food pellets containing YKS and then performed a fecal microbiota analysis, a microarray analysis for microRNAs (miRNAs) and an in vitro anti-tumor assay. The fecal microbiota analysis revealed that treatment with YKS partly reversed changes in the microbiota composition due to LLC implantation. Furthermore, a miRNA array analysis using blood serum showed that treatment with YKS restored the levels of miR-133a-3p/133b-3p, miR-1a-3p and miR-342-3p following LLC implantation to normal levels. A TargetScan analysis revealed that the epidermal growth factor receptor 1 signaling pathway is one of the major target pathways for these miRNAs. Furthermore, treatment with YKS restored the levels of miR-200b-3p and miR-200c-3p, a recognized mediator of cancer progression and controller of emotion, in the hypothalamus of mice bearing LLC. An in vitro assay revealed that a mixture of pachymic acid, saikosaponins a and d and isoliquiritigenin, which are all contained in YKS, exerted direct and additive anti-tumor effects. The present findings constitute novel evidence that YKS may exert an anti-tumor effect by reversing changes in the fecal microbiota and miRNAs circulating in the blood serum and hypothalamus, and the compounds found in YKS could have direct and additive anti-tumor effects.

Serotonin Receptor Binding Characteristics of Geissoschizine Methyl Ether, an Indole Alkaloid in Uncaria Hook

Background:

Geissoschizine methyl ether (GM) is one of the indole alkaloids in Uncaria hook, and an active ingredient of yokukansan (YKS) that improves behavioral and psychological symp-toms of dementia (BPSD) in patients with several types of dementia. The pharmacological action of GM has been related to various serotonin (5-HT) receptor subtypes.

Objective:

The aim of this article is to review the binding characteristics of GM to the 5-HT receptor sub-types in the brains using our own data and previous findings.

Methods:

Competitive receptor-binding and agonist/antagonist activity assays for several 5-HT receptor subtypes were performed. Moreover, the articles describing pharmacokinetics and brain distribution of GM were searched in PubMed.

Results:

GM bound the following 5-HT receptor subtypes: 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT4, 5-HT5A, 5-HT6, and 5-HT7. Among these receptors, GM had partial agonistic activity for 5-HT1A receptors and antagonistic activity for 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT7 receptors. Also, GM was me-tabolized by various CYP isoforms, mainly CYP3A4. Parent/unchanged GM was detected in both the blood and brain of rats after oral administration of YKS. In the brains, GM was presumed to bind to 5-HT1A, 5-HT2A, 5-HT2B, 5-HT2C, and 5-HT7 receptors on neuron-like large cells mainly in the frontal cor-tex.

Conclusion:

These results suggest that GM is a pharmacologically important alkaloid that regulates vari-ous serotonergic activities or functions by binding to multiple 5-HT receptor subtypes. Thus, this review provides recent 5-HT receptor-related evidence that GM is partly responsible for pharmacological effects of YKS.

Potential Application of Yokukansan as a Remedy for Parkinson’s Disease

Parkinson’s disease (PD), the second most common progressive neurodegenerative disorder, is characterized by complex motor and nonmotor symptoms. The clinical diagnosis of PD is defined by bradykinesia and other cardinal motor features, although several nonmotor symptoms are also related to disability, an impaired quality of life, and shortened life expectancy. Levodopa, which is used as a standard pharmacotherapy for PD, has limitations including a short half-life, fluctuations in efficacy, and dyskinesias with long-term use. There have been efforts to develop complementary and alternative therapies for incurable PD. Yokukansan (YKS) is a traditional herbal medicine that is widely used for treating neurosis, insomnia, and night crying in children. The clinical efficacy of YKS for treating behavioral and psychological symptoms, such as delusions, hallucinations, and impaired agitation/aggression subscale and activities of daily living scores, has mainly been investigated in the context of neurological disorders such as PD, Alzheimer’s disease, and other psychiatric disorders. Furthermore, YKS has previously been found to improve clinical symptoms, such as sleep disturbances, neuropsychiatric and cognitive impairments, pain, and tardive dyskinesia. Preclinical studies have reported that the broad efficacy of YKS for various symptoms involves its regulation of neurotransmitters including GABA, serotonin, glutamate, and dopamine, as well as the expression of dynamin and glutamate transporters, and changes in glucocorticoid hormones and enzymes such as choline acetyltransferase and acetylcholinesterase. Moreover, YKS has neuroprotective effects at various cellular levels via diverse mechanisms. In this review, we focus on the clinical efficacy and neuropharmacological effects of YKS. We discuss the possible mechanisms underpinning the effects of YKS on neuropathology and suggest that the multiple actions of YKS may be beneficial as a treatment for PD. We highlight the potential that YKS may serve as a complementary and alternative strategy for the treatment of PD.

Potential Application of Yokukansan as a Remedy for Parkinson's Disease

Parkinson's disease (PD), the second most common progressive neurodegenerative disorder, is characterized by complex motor and nonmotor symptoms. The clinical diagnosis of PD is defined by bradykinesia and other cardinal motor features, although several nonmotor symptoms are also related to disability, an impaired quality of life, and shortened life expectancy. Levodopa, which is used as a standard pharmacotherapy for PD, has limitations including a short half-life, fluctuations in efficacy, and dyskinesias with long-term use. There have been efforts to develop complementary and alternative therapies for incurable PD. Yokukansan (YKS) is a traditional herbal medicine that is widely used for treating neurosis, insomnia, and night crying in children. The clinical efficacy of YKS for treating behavioral and psychological symptoms, such as delusions, hallucinations, and impaired agitation/aggression subscale and activities of daily living scores, has mainly been investigated in the context of neurological disorders such as PD, Alzheimer's disease, and other psychiatric disorders. Furthermore, YKS has previously been found to improve clinical symptoms, such as sleep disturbances, neuropsychiatric and cognitive impairments, pain, and tardive dyskinesia. Preclinical studies have reported that the broad efficacy of YKS for various symptoms involves its regulation of neurotransmitters including GABA, serotonin, glutamate, and dopamine, as well as the expression of dynamin and glutamate transporters, and changes in glucocorticoid hormones and enzymes such as choline acetyltransferase and acetylcholinesterase. Moreover, YKS has neuroprotective effects at various cellular levels via diverse mechanisms. In this review, we focus on the clinical efficacy and neuropharmacological effects of YKS. We discuss the possible mechanisms underpinning the effects of YKS on neuropathology and suggest that the multiple actions of YKS may be beneficial as a treatment for PD. We highlight the potential that YKS may serve as a complementary and alternative strategy for the treatment of PD.

The Kampo medicine Yokukansan (YKS) enhances nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells

Accumulating evidence indicates that neurotrophic factor-like substances involved in the induction of neurotrophic factor synthesis may aid in the treatment of neurological disorders, such as Alzheimer's disease. Yokukansan (YKS), a traditional Kampo medicine, has been used for the treatment of anxiety and mood disorders. In the present study, we aimed to identify the signaling pathways associated with YKS-mediated enhancement of nerve growth factor (NGF)-induced neurite extension in rat pheochromocytoma (PC12) cells. Akt and extracellular-regulated kinase 1/2 (ERK1/2) phosphorylation levels were assessed by western blot analysis, in the presence of YKS and following the treatment with TrkA inhibitor, K252a. YKS treatment (NGF+YKS 0.5 group) enhanced NGF-induced neurite outgrowth and phosphorylation/activation of Akt and ERK1/2 in PC12 cells. Moreover, YKS-induced effects were inhibited by the treatment with the TrkA receptor antagonist K252a (NGF+YKS 0.5+K252a group); no significant difference in neurite outgrowth was observed between K252a-treated (NGF+YKS 0.5+K252a group) and NGF-K252a-treated cells (NGF+K252a group). However, neurite outgrowth in K252a-treated cells (NGF+K252a and NGF+YKS 0.5+K252a group) reached only one-third of the level in NGF-treated cells (NGF group). NGF-mediated Akt phosphorylation increased by YKS was also inhibited by K252a treatment (NGF+YKS 0.5+K252a group), but no significant difference in ERK1/2 phosphorylation was observed between NGF-YKS-K252a- and NGF-treated cells (NGF group). Our results indicate that YKS treatment enhanced NGF-induced neurite outgrowth via induction of Akt and ERK1/2 phosphorylation, following the binding of NGF to the TrkA receptor. These findings may be useful in the development of novel therapeutic strategies for the treatment of Alzheimer's disease.

Yokukansan, a traditional Japanese herbal medicine, enhances the anxiolytic effect of fluvoxamine and reduces cortical 5-HT2A receptor expression in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Yokukansan is a traditional Japanese herbal medicine that has been approved in Japan as a remedy for neurosis, insomnia, and irritability in children. It has also been reported to improve behavioral and psychological symptoms in patients with various forms of dementia.

AIM OF THE STUDY

To evaluate the usefulness of co-treatment with an antidepressant and an herbal medicine in the psychiatric field, the current study examined the effect of yokukansan on the anxiolytic-like effect of fluvoxamine in mice.

MATERIALS AND METHODS

The anxiolytic-like effect in mice was estimated by the contextual fear conditioning paradigm. Contextual fear conditioning consisted of two sessions, i.e., day 1 for the conditioning session and day 2 for the test session. The expression levels of 5-HT_1A and 5-HT_2A receptor in the mouse brain regions were quantified by western blot analysis.

RESULTS

A single administration of fluvoxamine (5-20 mg/kg, i.p.) before the test session dose-dependently and significantly suppressed freezing behavior in mice. In the combination study, a sub-effective dose of fluvoxamine (5 mg/kg, i.p.) significantly suppressed freezing behavior in mice that had been repeatedly pretreated with yokukansan (0.3 and 1 g/kg, p.o.) once a day for 6 days after the conditioning session. Western blot analysis revealed that the expression level of 5-HT_2A receptor was specifically decreased in the prefrontal cortex of mice that had been administered yokukansan and fluvoxamine. Furthermore, microinjection of the 5-HT_2A receptor antagonist ketanserin (5 nmol/mouse) into the prefrontal cortex significantly suppressed freezing behavior.

CONCLUSION

The present findings indicate that repeated treatment with yokukansan synergistically enhances the anxiolytic-like effect of fluvoxamine in the contextual fear conditioning paradigm in mice in conjunction with a decrease in 5-HT_2A receptor-mediated signaling in the prefrontal cortex. Therefore, combination therapy with fluvoxamine and yokukansan may be beneficial for the treatment of anxiety disorders.

Randomized phase II study of TJ-54 (Yokukansan) for postoperative delirium in gastrointestinal and lung malignancy patients

The present study evaluated the efficacy and safety of TJ-54 (Yokukansan; a traditional Japanese medicine) for the prevention and/or treatment of postoperative delirium in a randomized phase II trial of patients receiving surgery for gastrointestinal and lung malignancies. Patients ≥70 years of age who underwent surgery for gastrointestinal or lung malignancy were eligible for participation in the study. The 186 eligible patients were randomly assigned at a 1:1 ratio to receive TJ-54 or control during their peri-operative care (between 7 days prior to surgery and 4 days following surgery, except for the operation day). The signs and symptoms of delirium were assessed using the Diagnostic and Statistical Manual of Mental Disorders-IV by the investigator during the peri-operative period. A total of 186 eligible gastrointestinal or lung malignancy patients were analyzed (93, TJ-54; 93, control). There were no marked differences between the two randomized groups. The incidence of delirium was 6.5% (6 patients) in the TJ-54 group and 9.7% (9 patients) in the control group, with no significant difference (P=0.419). However, of the patients categorized with a mini-mental state examination (MMSE) score of ≤26, the incidence of postoperative delirium was 9.1% in the TJ-54 group and 26.9% in the control group [risk ratio, 0.338; 95% confidence interval (0.078–1.462), P=0.115]. Treatment with TJ-54 reduced the incidence of postoperative delirium compared with the control group. Although TJ-54 did not demonstrate any contribution to preventing or treating postoperative delirium in patients following surgery for gastrointestinal or lung malignancy, TJ-54 reduced the risk of postoperative delirium in the patients who were classified as MMSE ≤26. Further phase III studies with a larger sample size are required in order to clarify the effects of TJ-54 against postoperative delirium.

Yokukansan and Yokukansankachimpihange Ameliorate Aggressive Behaviors in Rats with Cholinergic Degeneration in the Nucleus Basalis of Meynert

Yokukansan (YKS) and yokukansankachimpihange (YKSCH) are traditional Japanese Kampo medicines. The latter comprises YKS along with the medicinal herbs Citrus unshiu peel and Pinellia tuber. Both of these Kampo medicines are indicated for the treatment of night crying and irritability in children and for neurosis and insomnia in adults. In recent clinical trials, YKS exhibited ameliorative effects on the behavioral and psychological symptoms of dementia, such as aggressiveness, excitement, and irritability. In the present study, we aimed to clarify the involvement of cholinergic degeneration in the nucleus basalis of Meynert (NBM) in the development of aggressiveness in rats. Subsequently, using this animal model, the effects of YKS and YKSCH on aggressiveness were compared and the mechanisms underlying these effects were investigated. L-Glutamic acid (Glu) was injected into the right NBM of rats to induce deterioration of cholinergic neurons. On day 8 after Glu injection, aggressive behaviors were evaluated using resident–intruder tests. After the evaluation, YKS or YKSCH was administered to rats with aggressive behaviors daily for 7 days. In some groups, the 5-HT_1A receptor antagonist WAY-100635 was coadministered with YKS or YKSCH over the same period. In other groups, locomotor activity was measured on days 12–14 after Glu injection. On day 15, immunohistochemistry was then performed to examine choline acetyltransferase (ChAT) activities in the NBM. Aggressive behaviors had developed on day 8 after Glu injection and were maintained until day 15. YKS and YKSCH significantly ameliorated the aggressive behaviors. These suppressive effects were entirely abolished following coadministration of WAY-100635. Finally, the number of ChAT-positive cells in the right NBM was significantly reduced on day 15 after Glu injection, and treatment with YKS or YKSCH did not ameliorate these reduced cell numbers. Our results show that unilateral Glu injections into the NBM of rats leads to the development of aggressive behaviors, which is thought to reflect cholinergic degeneration. YKS and YKSCH treatments ameliorated Glu-induced aggressive behaviors, and these effects were suggested to be mediated by 5-HT_1A receptor stimulation, but not by improvement of cholinergic degeneration.

Multiple Psychopharmacological Effects of the Traditional Japanese Kampo Medicine Yokukansan, and the Brain Regions it Affects

Yokukansan (YKS), a traditional Japanese Kampo medicine, has indications for use in night crying and irritability in children, as well as neurosis and insomnia. It is currently also used for the remedy of the behavioral and psychological symptoms of dementia (BPSD), such as aggressiveness, agitation, and hallucinations. In parallel with clinical evidence, a significant amount of fundamental researches have been undertaken to clarify the neuropsychopharmacological efficacies of YKS, with approximately 70 articles, including our own, being published to date. Recently, we reviewed the neuropharmacological mechanisms of YKS, including its effects on glutamatergic, serotonergic, and dopaminergic neurotransmission, and pharmacokinetics of the ingredients responsible for the effects. This review is aimed to integrate the information regarding the psychopharmacological effects of YKS with the brain regions known to be affected, to facilitate our understanding of the clinical efficacy of YKS. In this review, we first show that YKS has several effects that act to improve symptoms that are similar to BPSDs, like aggressiveness, hallucinations, anxiety, and sleep disturbance, as well as symptoms like tardive dyskinesia and cognitive deficits. We next provide the evidence showing that YKS can interact with various brain regions, including the cerebral cortex, hippocampus, striatum, and spinal cord, dysfunctions of which are related to psychiatric symptoms, cognitive deficits, abnormal behaviors, and dysesthesia. In addition, the major active ingredients of YKS, geissoschizine methyl ether and 18β-glycyrrhetinic acid, are shown to predominantly bind to the frontal cortex and hippocampus, respectively. Our findings suggest that YKS has multiple psychopharmacological effects, and that these are probably mediated by interactions among several brain regions. In this review, we summarize the available information about the valuable effects of a multicomponent medicine YKS on complex neural networks.

Neuropharmacological efficacy of the traditional Japanese Kampo medicine yokukansan and its active ingredients

Dementia is a progressive neurodegenerative disorder with cognitive dysfunction, and is often complicated by behavioral and psychological symptoms of dementia (BPSD) including excitement, aggression, and hallucinations. Typical and atypical antipsychotics are used for the treatment of BPSD, but induce adverse events. The traditional Japanese Kampo medicine yokukansan (YKS), which had been originated from the traditional Chinese medicine Yi-Gan-San, has been reported to improve BPSD without severe adverse effects. In the preclinical basic studies, there are over 70 research articles indicating the neuropharmacological efficacies of YKS. In this review, we first describe the neuropharmacological actions of YKS and its bioactive ingredients. Multiple potential actions for YKS were identified, which include effects on serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmissions as well as neuroprotection, anti-stress effect, promotion of neuroplasticity, and anti-inflammatory effect. Geissoschizine methyl ether (GM) in Uncaria hook and 18β-glycyrrhetinic acid (GA) in Glycyrrhiza were responsible for several pharmacological actions of YKS. Subsequently, we describe the pharmacokinetics of GM and GA in rats. These ingredients were absorbed into the blood, crossed the blood-brain barrier, and reached the brain, in rats orally administered YKS. Moreover, autoradiography showed that [(3)H]GM predominantly distributed in the frontal cortex and [(3)H]GA in the hippocampus. Thus, YKS is a versatile herbal remedy with a variety of neuropharmacological effects, and may operate as a multicomponent drug including various active ingredients.