Placental extract suppresses lipid droplet accumulation by autophagy during the differentiation of adipose-derived mesenchymal stromal/stem cells into mature adipocytes.

OBJECTIVE: Placental extract, which contains various bioactive compounds, has been used as traditional medicine. Many studies have demonstrated additional applications of placental extract and provided a scientific basis for the broad spectrum of its effects. We have previously reported that porcine placental extract (PPE) strongly suppresses adipogenesis in a 3T3-L1 preadipocyte cell line, inhibiting differentiation. This study aimed to examine the effect of PPE on the accumulation of lipid droplets (LD) in adipose-derived mesenchymal stromal/stem cells (ASC). RESULTS: The study findings revealed that PPE decreased the size of LD during the differentiation of ASC into mature adipocytes. RT-qPCR analysis revealed that PPE increased the gene expression of lysosomal acid lipase A (Lipa), a lipolysis-related gene, in ASC-differentiated adipocytes. However, no differences were noted in the adipocyte differentiation markers (Pparg, Cebpa, and Adipoq), or the adipogenesis-related genes (Dgat1, Dgat2, Fasn, Soat1, and Soat2). In addition, PPE promoted autophagosome formation, which was partially co-localized with the LD, indicating that PPE accelerated the degradation of LD by inducing autophagy (termed lipophagy) during the differentiation of ASC into mature adipocytes. These results suggest that the use of PPE may be a potential novel treatment for regulating adipogenesis for the treatment of obesity.

Development of a novel drug information provision system for Kampo medicine using natural language processing technology.

BACKGROUND: Kampo medicine is widely used in Japan; however, most physicians and pharmacists have insufficient knowledge and experience in it. Although a chatbot-style system using machine learning and natural language processing has been used in some clinical settings and proven useful, the system developed specifically for the Japanese language using this method has not been validated by research. The purpose of this study is to develop a novel drug information provision system for Kampo medicines using a natural language classifier® (NLC®) based on IBM Watson. METHODS: The target Kampo formulas were 33 formulas listed in the 17th revision of the Japanese Pharmacopoeia. The information included in the system comes from the package inserts of Kampo medicines, Manuals for Management of Individual Serious Adverse Drug Reactions, and data on off-label usage. The system developed in this study classifies questions about the drug information of Kampo formulas input by natural language into preset questions and outputs preset answers for the questions. The system uses morphological analysis, synonym conversion by thesaurus, and NLC®. We fine-tuned the information registered into NLC® and increased the thesaurus. To validate the system, 900 validation questions were provided by six pharmacists who were classified into high or low levels of knowledge and experience of Kampo medicines and three pharmacy students. RESULTS: The precision, recall, and F-measure of the system performance were 0.986, 0.915, and 0.949, respectively. The results were stable even with differences in the amount of expertise of the question authors. CONCLUSIONS: We developed a system using natural language classification that can give appropriate answers to most of the validation questions.

Green tea extract prevents CPT-11-induced diarrhea by regulating the gut microbiota.

Irinotecan (CPT-11) is an anticancer drug with indications for use in treating various cancers, but severe diarrhea develops as a side effect. We investigated the effects of green tea extract (GTE) on CPT-11-induced diarrhea, focusing on ß-glucuronidase and intestinal UGT1A1. When CPT-11 was administered to rats alone, the fecal water content was approximately 3.5-fold higher in this group than in the control group, and diarrhea developed. The fecal water content in the GTE-treated group was significantly higher than that in the control group, but the difference was smaller than that between the group treated with CPT-11 alone and the control group, and diarrhea improved. When CPT-11 was administered alone, the abundances of Bacteroides fragilis and Escherichia coli, which are ß-glucuronidase-producing bacteria, increased and interleukin-6 and interleukin-1ß mRNA levels in the colon increased, but GTE suppressed these increases. CPT-11 decreased colon UGT1A1 and short-chain fatty acid levels; however, this decrease was suppressed in the GTE-treated group. The findings that GTE decreases the abundance of ß-glucuronidase-producing bacteria and increases colon UGT1A1 levels, thereby decreasing the production of the active metabolite SN-38 in the intestinal tract, indicate that GTE ameliorates CPT-11-induced diarrhea.

Effect of Chimpi, dried citrus peel, on aquaporin-3 expression in HaCaT human epidermal keratinocytes.

BACKGROUND: Chimpi, the dried peel of Citrus unshiu or Citrus reticulata, has various pharmacological effects. Chimpi extract was recently shown to affect the skin, including its inhibitory effect against atopic dermatitis. In this study, we analyzed the effects of Chimpi extract on the functional molecule aquaporin-3 (AQP3), which is involved in water transport and cell migration in the skin. METHODS AND RESULTS: Chimpi extract was added to HaCaT human skin keratinocytes, and the AQP3 expression level was analyzed. A wound healing assay was performed to evaluate the effect of Chimpi extract on cell migration. The components of Chimpi extract and fractions obtained by liquid-liquid distribution studies were added to HaCaT cells, and AQP3 expression was analyzed. Chimpi extract significantly increased AQP3 expression in HaCaT cells at both the mRNA and protein levels. Immunocytochemical staining revealed that Chimpi extract also promoted the transfer of AQP3 to the cell membrane. Furthermore, Chimpi extract enhanced cell migration. Hesperidin, narirutin, and nobiletin did not increase AQP3 levels. Although the components contained in the fractions obtained from the chloroform, butanol, and water layer increased AQP3, the active components could not be identified. CONCLUSIONS: These results reveal that Chimpi extract may increase AQP3 levels in keratinocytes and increase the dermal water content. Therefore, Chimpi extract may be effective for the management of dry skin.

Dopaminergic mechanisms in the lateral hypothalamus regulate feeding behavior in association with neuropeptides.

This study investigated dopaminergic function in the lateral hypothalamus (LH) in the regulation of feeding behavior. Refeeding increased dopamine levels in the LH. Glucose injection also increased dopamine levels in the LH. When the retrograde tracer Fluoro-Gold (FG) was injected into the LH, FG-positive cells were found in the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNC), which were mostly tyrosine hydroxylase-positive. Injection of the dopamine D1 receptor agonist SKF 38393, but not the antagonist SCH 23390, into the LH increased food intake. Similarly, injection of the dopamine D2 receptor agonist quinpirole, but not the antagonist l-sulpiride, into the LH increased food intake. The effect of each agonist was blocked by its respective antagonist. Furthermore, injection of quinpirole, but not SKF 38393, decreased the mRNA level of preproorexin. In addition, injection of SKF 38393 decreased the mRNA levels of neuropeptide Y and agouti-related peptide, whereas the injection of quinpirole increased the mRNA level of proopiomelanocortin. These results indicate that food intake activates dopamine neurons projecting from the VTA/SNC to the LH through an increase in blood glucose levels, which terminates food intake by stimulation of dopamine D1 and D2 receptors. It is also possible that stimulation of dopamine D1 and D2 receptors in the LH inhibits feeding behavior through different neuropeptides.

Pregabalin increases food intake through dopaminergic systems in the hypothalamus.

Pregabalin is useful for treating neuropathic pain, but known to increase body weight as a side effect. To investigate the mechanism of this increase in body weight, we focused on dopamine in the lateral hypothalamus (LH) and examined the effects of pregabalin on dopamine levels in the LH and food intake. The dopamine levels in the LH was gradually decreased during fasting. When the animals were fed, dopamine levels in the LH was significantly increased, indicating that dopamine levels in the LH reflects energy state. The systemic injection of pregabalin tended to decrease dopamine levels in the LH after feeding. The dopamine levels in the LH was also significantly increased by glucose injection, which was inhibited by pregabalin. These results suggest that pregabalin inhibits dopaminergic function in the LH, which might increase food intake. To make these points clear, we examined the effects of pregabalin on food intake and blood glucose levels. Pregabalin significantly increased food intake, whereas pregabalin did not affect blood glucose levels. These results indicate that pregabalin stimulates feeding behavior, but not glucose metabolism. Moreover, the non-selective dopamine receptor antagonist cis-(Z)-flupenthixol injected into the LH significantly increased food intake, though neither the dopamine D1 receptor antagonist SCH 23390 nor the D2 receptor antagonist l-sulpiride injected into the LH affected food intake. These results indicate that the inhibition of dopaminergic function in the LH increases food intake. In conclusion, the present results suggest that pregabalin increases food intake through the inhibition of dopaminergic functions in the LH.

Analgesic effect of mineral cream containing natural spa minerals for use on the skin.

Previous studies have shown that dissolved substances in some natural hot springs have analgesic/anti-nociceptive and anti-inflammatory actions. However, the mechanisms underlying how such dissolved substances exert these actions are not fully understood. In the present study on mice, we examined the analgesic/anti-nociceptive and anti-inflammatory properties of a mineral cream containing natural hot spring ingredients. The anti-nociceptive effects of the mineral cream were assessed by using the von Frey test. Application of the mineral cream to the hind paw of mice produced a significant anti-nociceptive effect compared to control. The anti-nociceptive effects of the mineral cream were also assessed following the injection of complete Freund's adjuvant (CFA) into the hind paws of mice after pre-treatment for one or four weeks with the mineral cream. Histological experiments with light microscopy showed that the mineral cream did not reduce inflammation caused by the CFA treatment. In addition, the mineral cream did not inhibit oxidative stress as evidenced by increased levels of oxidative metabolites (d-ROMs) and biological anti-oxidant potential (BAP). These results suggest that the mineral cream does not exert a protective effect against inflammation, and that the constituents of the mineral cream may produce their anti-nociceptive effects transdermally via different mechanisms including the nervous system.

Rikkunshito prevents paclitaxel-induced peripheral neuropathy through the suppression of the nuclear factor kappa B (NFκB) phosphorylation in spinal cord of mice.

Peripheral neuropathy is the major side effect caused by paclitaxel, a microtubule-binding antineoplastic drug. Paclitaxel-induced peripheral neuropathy causes a long-term negative impact on the patient's quality of life. However, the mechanism underlying paclitaxel-induced peripheral neuropathy is still unknown, and there is no established treatment. Ghrelin is known to attenuate thermal hyperalgesia and mechanical allodynia in chronic constriction injury of the sciatic nerve, and inhibit the activation of nuclear factor kappa B (NFκB) in the spinal dorsal horn. Rikkunshito (RKT), a kampo medicine, increases the secretion of ghrelin in rodents and humans. Thus, RKT may attenuate paclitaxel-induced peripheral neuropathy by inhibiting phosphorylated NFκB (pNFκB) in the spinal cord. We found that paclitaxel dose-dependently induced mechanical hyperalgesia in mice. Paclitaxel increased the protein levels of spinal pNFκB, but not those of spinal NFκB. NFκB inhibitor attenuated paclitaxel-induced mechanical hyperalgesia suggesting that the activation of NFκB mediates paclitaxel-induced hyperalgesia. RKT dose-dependently attenuated paclitaxel-induced mechanical hyperalgesia. Ghrelin receptor antagonist reversed the RKT-induced attenuation of paclitaxel-induced mechanical hyperalgesia. RKT inhibited the paclitaxel-induced increase in the protein levels of spinal pNFκB. Taken together, the present study indicates that RKT exerts an antihyperalgesic effect in paclitaxel-induced neuropathic pain by suppressing the activation of spinal NFκB.

Involvement of glutamatergic N-methyl-d-aspartate receptors in the expression of increased head-dipping behaviors in the hole-board tests of olfactory bulbectomized mice.

Olfactory bulbectomized (OB) mice produce agitated anxiety-like behaviors in the hole-board test, which was expressed by an increase in head-dipping counts and a decrease in head-dipping latencies. However, the associated mechanisms remain unclear. In the present study, MK-801 (10, 100µg/kg), a selective N-methyl-d-aspartate (NMDA) receptor antagonist, significantly and dose-dependently suppressed the increased head-dipping behaviors in OB mice, without affecting sham mice. Similar results were obtained with another selective NMDA receptor antagonist D-AP5 treatment in OB mice. On the other hand, muscimol, a selective aminobutyric acid type A (GABAA) receptor agonist produced no effects on these hyperemotional behaviors in OB mice at a dose (100µg/kg) that produced anxiolytic-like effects in sham mice. Interestingly, glutamine contents and glutamine/glutamate ratios were significantly increased in the amygdala and frontal cortex of OB mice compared to sham mice. Based on these results, we concluded that the glutamatergic NMDA receptors are involved in the expression of increased head-dipping behaviors in the hole-board tests of OB mice. Accordingly, the changes in glutamatergic transmission in frontal cortex and amygdala may play important roles in the expression of these abnormal behaviors in OB mice.

Olanzapine-induced hyperglycemia: possible involvement of histaminergic, dopaminergic and adrenergic functions in the central nervous system.

BACKGROUND/AIMS: Atypical antipsychotic drugs such as olanzapine are known to induce metabolic disturbance. We have already shown that olanzapine induces hepatic glucose production through the activation of hypothalamic adenosine 5'-monophosphate-activated protein kinase (AMPK). However, it is unclear how olanzapine activates hypothalamic AMPK. Since olanzapine is known to antagonize several receptors, including histaminergic, muscarinic, serotonergic, dopaminergic and adrenergic receptors, we examined the effect of each receptor antagonist on blood glucose levels in mice. Moreover, we also investigated whether these antagonists activate hypothalamic AMPK. METHODS: Male 6-week-old ICR mice were used. Blood glucose levels were determined by the glucose oxidase method. AMPK expression was measured by Western blotting. RESULTS: Central administration of olanzapine (5-15 nmol i.c.v.) dose-dependently increased blood glucose levels in mice, whereas olanzapine did not change blood insulin levels. Histamine H1 receptor antagonist chlorpheniramine (1-10 µg i.c.v.), dopamine D2 receptor antagonist L-sulpiride (1-10 µg i.c.v.) and α1-adrenoceptor antagonist prazosin (0.3-3 µg i.c.v.) also significantly increased blood glucose levels in mice. In contrast, the blood glucose levels were not affected by muscarinic M1 receptor antagonist dicyclomine (1-10 µg i.c.v.) or serotonin 5-HT2A receptor antagonist M100907 (1-10 ng i.c.v.). Olanzapine-induced hyperglycemia was inhibited by the AMPK inhibitor compound C, and AMPK activator AICAR (10 ng to 1 µg i.c.v.) significantly increased blood glucose levels. Olanzapine (15 nmol), chlorpheniramine (10 µg), L-sulpiride (10 µg) and prazosin (3 µg) significantly increased phosphorylated AMPK in the hypothalamus of mice. CONCLUSION: These results suggest that olanzapine activates hypothalamic AMPK by antagonizing histamine H1 receptors, dopamine D2 receptors and α1-adrenoceptors, which induces hyperglycemia.

Olanzapine induces glucose intolerance through the activation of AMPK in the mouse hypothalamus.

Treatment with atypical antipsychotic drugs is known to increase the risk of glucose intolerance and diabetes. However, the mechanism of this effect is unclear. Since central adenosine 5'-monophosphate-activated protein kinase (AMPK) plays an important role in regulating nutrient homeostasis, the present study was performed to examine the involvement of central AMPK in the glucose intolerance induced by olanzapine, an atypical antipsychotic drug, in mice. Acute intraperitoneal treatment with olanzapine dose-dependently increased blood glucose levels in the glucose tolerance test. Intracerebroventricular administration of olanzapine also increased blood glucose levels in the glucose tolerance test. The glucose intolerance induced by both intraperitoneal and intracerebroventricular treatment with olanzapine was significantly attenuated by intracerebroventricular pretreatment with the AMPK inhibitor compound C. Intracerebroventricular treatment with the AMPK activator AICAR increased blood glucose levels in the glucose tolerance test, and this increase was inhibited by compound C. Moreover, the hypothalamic level of phosphorylated AMPK after glucose injection was significantly increased by intracerebroventricular pretreatment with olanzapine. Olanzapine did not affect plasma glucagon and insulin levels. Our results indicate that acute treatment with olanzapine causes glucose intolerance through the activation of hypothalamic AMPK. The present study suggests that the inhibition of central AMPK activity may have a therapeutic effect on the metabolic disturbance induced by atypical antipsychotic drugs.

Involvement of the benzodiazepine system in the anxiolytic-like effect of Yokukansan (Yi-gan san).

The traditional Japanese Kampo medicine Yokukansan (YKS, Yi-gan san in Chinese) has been demonstrated to improve the behavioral and psychological symptoms of dementia (BPSD), such as anxiety, hallucinations, agitation and irritability. The aim of this study was to elucidate the mechanism of the anxiolytic-like effects of YKS and Chotoko, which is an active component of YKS. Oral treatment with YKS (300 and 1000 mg/kg) significantly increased the number of head-dipping behaviors in mice in the hole-board test. Head-dipping behavior in mice was also significantly increased by treatment with Chotoko (50 and 100mg/kg, p.o.). In addition, oral treatment with the water-extracted fractions from YKS (YKS-W; 250 and 500 mg/kg, p.o.) and Chotoko (Chotoko-W; 10 and 30 mg/kg) significantly increased the number of head-dipping behaviors in mice. On the other hand, treatment with the methanol-extracted fraction of YKS (YKS-Met; 15 and 30 mg/kg, p.o.) did not affect head-dipping behavior. The total distance and number of rearing behaviors were not affected by treatment with any of these drugs. The increase in the number of head-dipping behaviors by treatment with YKS-W (500 mg/kg, p.o.) and Chotoko-W (30 mg/kg, p.o.) was inhibited by pretreatment with the benzodiazepine receptor antagonist flumazenil (1mg/kg, i.v.). In the elevated plus-maze test, the percentage of time spent in open arms was increased in YKS (1000 mg, p.o.) treatment. Based on these results, we suggest that YKS produces an anxiolytic-like effect mediated by the benzodiazepine system. Chotoko is an effective component of YKS for producing an anxiolytic-like effect. The effective compound(s) should be contained, at least in part, in the water-soluble fraction of YKS.

Structure-antitussive activity relationships of naltrindole derivatives. Identification of novel and potent antitussive agents.

We have previously reported antitussive effects of naltrindole (NTI), a typical delta opioid receptor antagonist, in a rat model. The ED50 values of NTI by intraperitoneal and peroral injections were 104 microg/kg and 1840 microg/kg, respectively, comparable to those of codeine. Codeine, one of the most reliable centrally acting antitussive drugs, has micro agonist activity and thus the same side effects as morphine, e.g., constipation, dependency, and respiratory depression. Because NTI is a delta opioid antagonist, its derivatives have potential as highly potent antitussives, free from the mu opioid agonist side effects. We attempted to optimize the NTI derivatives to develop novel antitussive agents. On the basis of the studies of structure-antitussive activity relationships of alkyl substituted NTI derivatives, we designed NTI derivatives with extra ring fused structures. As a clinical candidate, we identified a highly potent new compound, (5R,9R,13S,14S)-17-cyclopropylmethyl-6,7-didehydro-4,5-epoxy-5',6'-dihydro-3-methoxy-4'H-pyrrolo[3,2,1-ij]quinolino[2',1':6,7]morphinan-14-ol (5b) methanesulfonate (TRK-850) which was effective even by oral administration (ED50 6.40 microg/kg).

Effects of histamine H(1) receptor antagonists on depressive-like behavior in diabetic mice.

We previously reported that streptozotocin-induced diabetic mice showed depressive-like behavior in the tail suspension test. It is well known that the central histaminergic system regulates many physiological functions including emotional behaviors. In this study, we examined the role of the central histaminergic system in the diabetes-induced depressive-like behavior in the mouse tail suspension test. The histamine contents in the hypothalamus were significantly higher in diabetic mice than in non-diabetic mice. The histamine H(1) receptor antagonist chlorpheniramine (1-10 mg/kg, s.c.) dose-dependently and significantly reduced the duration of immobility in both non-diabetic and diabetic mice. In contrast, the selective histamine H(1) receptor antagonists epinastine (0.03-0.3 microg/mouse, i.c.v.) and cetirizine (0.01-0.1 microg/mouse, i.c.v.) dose-dependently and significantly suppressed the duration of immobility in diabetic mice, but not in non-diabetic mice. Spontaneous locomotor activity was not affected by histamine H(1) receptor antagonists in either non-diabetic or diabetic mice. In addition, the number and affinity of histamine H(1) receptors in the frontal cortex were not affected by diabetes. In conclusion, we suggest that the altered neuronal system mediated by the activation of histamine H(1) receptors is involved, at least in part, in the depressive-like behavior seen in diabetic mice.

Anti-hyperglycemic effects of plum in a rat model of obesity and type 2 diabetes, Wistar fatty rat.

Dried plums, considered a healthy food in the West and used as medicine in India, contain phenolic compounds with protective actions against age-related diseases. Effects of oral plum ekisu (concentrated juice) on lipid and glucose tolerance were assessed in insulin-resistant obese Wistar fatty rats. Plum ingestion decreased blood glucose (P < 0.05) and plasma triglyceride concentrations (P < 0.01) compared with controls. Plum treatment for 2 weeks reduced areas under the curve (AUCs) for glucose and insulin during a glucose tolerance test. In db/db mice, plum decreased these AUCs, and also blood glucose during an insulin tolerance test. Plum treatment significantly increased plasma adiponectin concentrations and PPARgamma mRNA expression in adipose tissue from Wistar fatty rats. Plum thus may increase insulin sensitivity in these rats via adiponectin-related mechanisms.

Implication of the descending dynorphinergic neuron projecting to the spinal cord in the (+)-matrine- and (+)-allomatrine-induced antinociceptive effects.

We previously reported that either (+)-matrine (matridin-15-one) or (+)-allomatrine (the C-6 epimer of matrine)-induced antinociceptive effect was attenuated by s.c. pretreatment with a kappa-opioid receptor (KOR) antagonist nor-binaltorphimine (nor-BNI), indicating the critical role of KORs in antinociceptive effects induced by these alkaloids. In the present study, we found that i.c.v. administration of either (+)-matrine- or (+)-allomatrine induced antinociceptive effects in the mouse tail-flick and warm-plate test, whereas these alkaloids when given spinally failed to induce antinociception. In the guanosine-5'-O-(3-[(35)S]thio)trisphosphate ([(35)S]GTPgammaS) binding assay, we demonstrated that neither (+)-matrine nor (+)-allomatrine produced the stimulation of [(35)S]GTPgammaS binding in the membranes of the spinal cord, indicating that (+)-matrine- and (+)-allomatrine-induced supraspinal antinociceptive actions was not due to a direct stimulation of KORs by these alkaloids. Therefore, we next investigated the involvement of dynorphin A (1-17) release at the spinal or supraspinal site in (+)-matrine- or (+)-allomatrine-induced antinociception. The i.c.v. pretreatment with an antiserum against dynorphin A (1-17) could not affect the antinociceptive effect induced by s.c. treatment of (+)-matrine. In contrast, the s.c.-administered (+)-matrine- and (+)-allomatrine-induced antinociceptive effect was significantly attenuated by i.t. pretreatment of an antiserum against dynorphin A (1-17). The present data suggest that either (+)-matrine or (+)-allomatrine when given i.c.v. may stimulate the descending dynorphinergic neuron, resulting in the stimulation of KORs in the spinal cord, and this phenomenon in turn produces the antinociception in mice.

Pharmacokinetic and pharmacodynamic profiles of the antitussive principles of Glycyrrhizae radix (licorice), a main component of the Kampo preparation Bakumondo-to (Mai-men-dong-tang).

We examined the pharmacokinetic and pharmacodynamic properties of liquiritin apioside, a main antitussive component of Glycyrrhizae radix (licorice), with regard to its antitussive effect in guinea pigs. The peak plasma concentration of the unchanged compound was observed 15 min after the administration of liquiritin apiosaide. The plasma concentration then gradually decreased and was almost undetectable 4 h after administration. Liquiritigenin, a des-glycoside of liquiritin apioside, appeared in the plasma 2 h after the administration of liquiritin apioside and remained for more than 6 h after administration. The plasma concentration of unchanged liquiritigenin was observed 15 min after administration and then gradually increased for more than 6 h after administration. When the antitussive effects of liquiritin apioside, liquiritin and liquiritigenin, at respective doses of 30 mg/kg, p.o., were examined 1 h after administration, liquiritin apioside and liquiritigenin caused a significant reduction in the number of capsaicin-induced coughs. However, at the same dose, liquiritin had no significant effect on the number of capsaicin-induced coughs. On the other hand, when the antitussive effects of liquiritin apioside, liquiritin and liquiritigenin, at doses of 30 mg/kg, p.o., were examined 4 h after administration, each caused a more than 40% reduction in the number of capsaicin-induced coughs. The present results suggest that G. radix (licorice) may produce a persistent antitussive effect, and that liquiritin apioside plays an important role in the earlier phase, while liquiritigenin, which is a metabolite of liquiritin apioside and liquiritin, plays an important role in the late phase.

Antitussive principles of Glycyrrhizae radix, a main component of the Kampo preparations Bakumondo-to (Mai-men-dong-tang).

We attempted to elucidate the antitussive principles of Glycyrrhizae radix, a main component of Bakumondo-to (Mai-men-dong-tang). Although the 50% methanol-eluted fraction (100 mg/kg, p.o.) caused a more than 60% reduction in the number of capsaicin-induced coughs, neither the water-eluted nor 100% ethanol-eluted fractions of water extract of G. radix had antitussive effects. The water extract of G. radix contained high levels of liquiritin, liquiritin apioside, isoliquiritin, isoliquiritin apioside and glycyrrhizin. On the other hand, the 50% methanol-eluted fraction contained mainly liquiritin and liquiritin apioside, but not the other compounds. Liquiritin apioside (3-30 mg/kg, p.o.), but not liquiritin, isoliquiritin, isoliquiritin apioside or glycyrrhizin, dose-dependently inhibited the number of coughs. Methysergide, a serotonin receptor antagonist, antagonized the antitussive effect of liquiritin apioside. However, the antitussive effect of liquiritin apioside was not antagonized by naloxone. Pretreatment with glibenclamide (3 mg/kg, i.p.), an ATP-sensitive potassium channel blocker, also significantly reduced the antinociceptive effect of liquiritin apioside. These results suggest that G. radix contains a potent antitussive compound, liquilitin apioside, whose antitussive effect may depend on both peripheral and central mechanisms.