Pentobarbital-induced Sleep In Mice Research Articles

Lactuca sativa L. Extract Enhances Sleep Duration Through Upregulation of Adenosine A1 Receptor and GABAA Receptors Subunits in Pentobarbital-Injected Mice.

We investigated the effects of Lactuca sativa L. extracts (Lactuc) on pentobarbital-induced sleep in mice to elucidate the mechanisms underlying its impact on sleep quality. Mice were randomly assigned to five groups: control, positive control (diazepam 2 mg/kg b.w.), and three groups orally administered with Lactuc (50, 100, and 200 mg/kg b.w.). After 2 weeks of oral administration and intraperitoneal injections, the mice were killed. We found that the Lactuc-administered groups had significantly reduced sleep latency and increased sleep duration compared with the control group. Furthermore, the oral administration of Lactuc induced a significant increase in mRNA expression and protein expression of adenosine A1 receptor in the brains compared with the expressions in the control group. In addition, the Lactuc-administered groups exhibited significantly higher levels of mRNA expressions of GABAA receptors subunits α2, β2, γ1, and, γ2 in the brain tissue. Therefore, we suggest that Lactuc could be used to develop natural products that effectively improve sleep quality and duration.

Sleep-potentiating Effects of Passiflora incarnata and ‘Heukharang’, a Novel Korean Lactuca sativa, on Pentobarbital-induced Sleep in Mice

Sleep-potentiating Effects of Passiflora incarnata and ‘Heukharang’, a Novel Korean Lactuca sativa, on Pentobarbital-induced Sleep in Mice

The possible mechanism of Datura stramonium on pentobarbital-induced sleep in mice

Background Insomnia leads to the development of mental problems and missing of accuracy in affected persons. Various investigations have previously revealed which medicinal plants play a role in the improvement of insomnia. In this study, we evaluated the effect of hydro-alcoholic extract of Datura stramonium on insomnia in mice. Methods The extracts and fractions at different concentrations were injected intraperitoneally (i.p.) to mice 30 min before the sodium pentobarbital (30 mg/kg, i.p.). Additionally, the blood was collected from cardiac and serum separated to measure brain-derived neurotrophic factor (BDNF). The LC-MS was done to identify the active components. Flumazenil or naloxone were also applied to study the possible mechanism of extract. The PC12 cells were then exposed to different doses of extract and fractions, in order to evaluate cytotoxicity by MTT assay and the measured LD50. Results The hydro-alcoholic extracts of calyx, seed and petal elevated sleep duration and decreased sleep latency. In addition, water, ethyl acetate and n-butanol fractions of hydro-alcoholic extract of petal increased sleep duration. Of note, Naloxone significantly reversed the hypnotic effect of the extract. The extract increased the level of BDNF in serums. As well, the toxicity assessment revealed that the extracts had not toxic on PC12 cells. The LD50 value was obtained as 4.8 g/kg. Conclusion This research demonstrated that D. stramonium (including seed, petal and calyx) increased the hypnotic effect without neurotoxicity on PC12 cells. Sleep induction may be related to its active ingredients as well as the effect on opioid receptors.

Hypnotic Effects of Lactobacillus fermentum PS150TM on Pentobarbital-Induced Sleep in Mice.

The bidirectional communication between the gastrointestinal tract and the central nervous system appears to be functionally linked to the intestinal microbiome, namely the microbiome–gut–brain axis (MGBA). Probiotics with health benefits on psychiatric or neurological illnesses are generally called psychobiotics, and some of them may also be able to improve sleep by targeting the MGBA. This study aimed to investigate the effects of a psychobiotic strain, Lactobacillus fermentum PS150TM (PS150TM), on sleep improvement by using a pentobarbital-induced sleep mouse model. Compared with the vehicle control group, the oral administration of PS150TM, but not the other L. fermentum strains, significantly decreased the sleep latency and increased the sleep duration of mice, suggesting strain-specific sleep-improving effects of PS150TM. Moreover, the ingestion of diphenhydramine, an antihistamine used to treat insomnia, as a drug control group, only increased the sleep duration of mice. We also found that the sleep-improving effects of PS150TM are time- and dose-dependent. Furthermore, the oral administration of PS150TM could attenuate a caffeine-induced sleep disturbance in mice, and PS150TM appeared to increase the expression of the gene encoding the adenosine 1 receptor in the hypothalamus of mice, as assessed by quantitative real-time polymerase chain reaction. Taken together, our results present a potential application of PS150TM as a dietary supplement for sleep improvement.

\u22069-Tetrahydrocannabinol, a major marijuana component, enhances the anesthetic effect of pentobarbital through the CB1 receptor

Purpose∆9-Tetrahydrocannabinol (∆9-THC) and cannabidiol (CBD), major psychoactive constituents of marijuana, induce potentiation of pentobarbital-induced sleep in mice. We have elucidated the mechanism of enhancement of the anesthetic effect of pentobarbital by cannabinoids.MethodsWe carried out pharmacological experiment and cannabinoid1 (CB1) receptor binding assay using CB1 antagonists to clarify whether the CB1 receptor is involved in the synergism or not. The affinities of cannabinoids for the CB1 receptor in the mouse brain synaptic membrane were evaluated using a specific CB1 ligand, [3H]CP55940.ResultsAlthough the potentiating effect of ∆9-THC on pentobarbital-induced sleep was attenuated by co-administration of CB1 receptor antagonists, such as SR141716A and AM251, at a dose of 2 mg/kg, intravenously (i.v.) to mice, the CBD-enhanced pentobarbital-induced sleep was not inhibited by SR141716A. The inhibitory constant (Ki) values of ∆9-THC and CBD were 6.62 and 2010 nM, respectively, showing a high affinity of ∆9-THC and a low affinity of CBD for the CB1 receptor, respectively. A high concentration of pentobarbital (1 mM) did not affect specific [3H]CP55940 binding on the mouse brain synaptic membrane.ConclusionsThese results suggest that binding of ∆9-THC to the CB1 receptor is involved in the synergism with pentobarbital, and that potentiating effect of CBD with pentobarbital may differ from that of ∆9-THC. We successfully demonstrated that ∆9-THC enhanced the anesthetic effect of pentobarbital through the CB1 receptor.

Hypnotic Effect of Red Cabbage (Brassica oleracea) on Pentobarbital-Induced Sleep in Mice.

Objective:The present study was performed to investigate the effect of hydroalcoholic extract of red cabbage and its fractions on sleeping behavior in mice.Materials and Methods:The extract and its fractions were injected to mice and sleep duration as well as sleep latency were recorded. Furthermore, toxicity of the extract was determined both in vivo and in vitro.Results:The extract increased sleep duration at doses of 50–200mg/kg (P < 0.001). This observed hypnotic effect was comparable to that of diazepam (3mg/kg) (P < 0.001 in comparison with control group). Ethyl acetate, n-butanol, and aqueous fractions could increase sleep duration (P < 0.001). The sleep latency was decreased by the extract (P < 0.001) and only ethyl acetate fraction (P < 0.001). LD50 value for red cabbage extract was 2.4g/kg. There was no toxic effect on viability of cultured neuronal cells (PC12). Rotarod test results showed that there were no significant differences between the extract groups and the control group.Conclusion:The results suggest that red cabbage potentiates pentobarbital hypnosis without any toxic effect. The main component(s) responsible for this effect is most likely to be intermediate polar agent(s) such as flavonoids, which are found in ethyl acetate fraction of this plant.

Sleep-Promoting Effects and Possible Mechanisms of Action Associated with a Standardized Rice Bran Supplement.

Natural sleep aids are becoming more popular due to the widespread occurrence of sleep disorders. The objective of this study was to assess the sleep-promoting effects of rice bran—a product that is considered as a functional ingredient. To evaluate the sleep-promoting effects of a standardized rice bran supplement (RBS), we employed a pentobarbital-induced sleep test and conducted analyses of sleep architecture. In addition, the effect of RBS on a caffeine-induced sleep disturbance was investigated. Oral administration of RBS (500 and 1000 mg/kg) produced a significant decrease in sleep latency and increase in sleep duration in pentobarbital-induced sleep in mice. Moreover, both RBS (1000 mg/kg) and doxepin hydrochloride (histamine H1 receptor antagonist, 30 mg/kg) counteracted a caffeine-induced sleep disturbance in mice. In terms of sleep phases, RBS (500 mg/kg) promoted non-rapid eye movement sleep for the first 3 h following its administration. Lastly, we unveiled a possible mechanism for RBS action as the hypnotic effect of RBS was blocked by a histamine H1 receptor agonist. The present study revealed sleep-promoting effects of RBS using various animal assays. Such effects seem to be mediated through the histaminergic system. Our findings suggest that RBS may be a promising natural aid for relieving sleep problems.

Biotransformation of monosodium glutamate to gamma-aminobutyric acid by isolated strain Lactobacillus brevis L-32 for potentiation of pentobarbital-induced sleep in mice

ABSTRACTIn the current study, we investigated the biotransformation of monosodium glutamate (MSG) to gamma-aminobutyric acid (GABA) by the growing and resting cells from an isolated bacterial strain, Lactobacillus brevis. This strain is a high GABA-producing strain that was identified and isolated from natural kimchi. We gathered the experiment results by design of response surface methodology (RSM) for optimum condition for GABA production and results indicated the optimum culture temperature (35°C) and culture time (58 h). Using resting cells from the same culture batch in the substrate-containing buffer, approximately 3.98 g/l of GABA was produced at a conversion rate of 65.6%. GABA-treated mice showed significantly increased sleep duration compared to that of a control group (p < 0.05) in the pentobarbital-induced sleep test using a hypnotic dose. These results suggest that biotransformed GABA could potentially be used a novel nutraceutical supplement for sleep.

A tryptic hydrolysate from bovine milk αs1-casein enhances pentobarbital-induced sleep in mice via the GABAA receptor

Studies have shown that enzymatic hydrolysis of casein, the primary protein component of cow’s milk, produces peptides with various biological activities, and some of these peptides may have sleep-promoting effects. In the present study, we evaluated the sedative and sleep-promoting effects of bovine αS1-casein tryptic hydrolysate (CH), containing a decapeptide αS1-casein known as alpha-casozepine. CH was orally administered to ICR mice at various concentrations (75, 150, 300, or 500mg/kg). An hour after administration, assessment of its sedative (open-field and rota-rod tests) and sleep-potentiating effects (pentobarbital-induced sleeping test and EEG monitoring) were conducted. Although a trend can be observed, CH treatment did not significantly alter the spontaneous locomotor activity and motor function of mice in the open-field and rota-rod tests. On the other hand, CH (150mg/kg, respectively) enhanced the sleep induced by pentobarbital sodium in mice. It also promoted slow-wave (delta) EEG activity in rats; a pattern indicative of sleep or relaxation. These behavioral results indicate that CH has sleep-promoting effects, but no or has minimal sedative effects. To elucidate the probable mechanism behind the effects of CH, we examined its action on intracellular chloride ion influx in cultured human neuroblastoma cells. CH dose-dependently increased chloride ion influx, which was blocked by co-administration of bicuculline, a competitive GABAA receptor antagonist. Taken together, the results of the present study suggest that CH has sleep-promoting properties which are probably mediated through the GABAA receptor–chloride ion channel complex.

Hypnotic Effect of Ocimum basilicum on Pentobarbital-Induced Sleep in Mice.

BackgroundSleep disorders are accompanied by several complications, and currently used soporific drugs can induce unwanted effects such as psychomotor impairment, tolerance, amnesia, and rebound insomnia.ObjectivesThe present study was carried out to investigate if Ocimum basilicum has a sleep-prolonging effect.Materials and MethodsThis work was an experimental study on 72 mice which were randomly divided into 9 groups: saline (control); diazepam (3 mg/kg, positive control); hydro-alcoholic extract (HAE) of Ocimum basilicum (25, 50, or 100 mg/kg); ethyl acetate fraction (EAF, 50 mg/kg); n-butanol fraction (NBF, 50 mg/kg); water fraction (WF, 50 mg/kg); and saline containing 10% DMSO (vehicle for EAF and NBF). All the test compounds were injected intraperitoneally (IP) 30 minutes before pentobarbital administration (30 mg/kg). Duration and latency of pentobarbital-induced sleep were recorded. Also, LD50 of HAE was determined and the cytotoxicity of HAE was tested on neural and fibroblast cells using the MTT assay.ResultsHAE increased the duration of pentobarbital-induced sleep at doses of 25, 50, and 100 mg/kg (P < 0.001). The hypnotic effect of HAE was comparable to that induced by diazepam. Similarly, WF, EAF, and NBF at 50 mg/kg could increase sleep duration. The sleep latency was decreased by HAE (P < 0.01 - P < 0.001) and NBF (P < 0.001), but not by WF and EAF. The LD50 value for HAE was found to be 2.4 g/kg. HAE had no effect on the viability of neuronal PC12 cells and L929 fibroblast cells.ConclusionsThe present data demonstrated that Ocimum basilicum potentiates sleeping behaviors without any cytotoxicity. The main component (s) responsible for the hypnotic effects of this plant is most likely a non-polar agent (s) which is found in NBF. Isolation of the active constituents may yield a novel sedative drug.

Sedative-Hypnotic and Receptor Binding Studies of Fermented Marine Organisms

This study was performed to investigate the sedative-hypnotic activity of γ-aminobutyric acid (GABA)-enriched fermented marine organisms (FMO), including sea tangle (FST) and oyster (FO) by Lactobacillus brevis BJ20 (L. brevis BJ20). FST and FO were tested for their binding activity of the GABAA-benzodiazepine and 5-HT2C receptors, which are well-known molecular targets for sleep aids. We also measured the sleep latency and sleep duration during pentobarbital-induced sleep in mice after oral administration of FST and FO. In GABAA and 5-HT2C receptor binding assays, FST displayed an effective concentration-dependent binding affinity to GABAA receptor, similar to the binding affinity to 5-HT2C receptor. FO exhibited higher affinity to 5-HT2C receptor, compared with the GABAA receptor. The oral administration of FST and FO produced a dose-dependent decrease in sleep latency and increase in sleep duration in pentobarbital-induced hypnosis. The data demonstrate that FST and FO possess sedative-hypnotic activity possibly by modulating GABAA and 5-HT2C receptors. We propose that FST and FO might be effective agents for treatment of insomnia.

Positive effects of β-amyrin on pentobarbital-induced sleep in mice via GABAergic neurotransmitter system

Sleep loss, insomnia, is considered a sign of imbalance of physiological rhythm, which can be used as pre-clinic diagnosis of various neuropsychiatric disorders. The aim of the present study is to understand the pharmacological actions of α- or β-amyrin, natural triterpene compound, on the sleep in mice. To analyze the sleeping behavior, we used the well-known pentobarbital-induced sleeping model after single administration of either α- or β-amyrin. The sleeping onset time was remarkably decreased and duration was prolonged by β-amyrin (1, 3, or 10mg/kg) but not by α-amyrin (1, 3, or 10mg/kg). These effects were significantly blocked by GABAA receptor antagonist, bicuculline. Moreover, β-amyrin increased brain GABA level compared to the vehicle administration. Overall, the present study suggests that β-amyrin would enhance the total sleeping behavior in pentobarbital-induced sleeping model via the activation of GABAergic neurotransmitter system through GABA content in the brain.

Analgesic activity of DaChuanXiongFang after intranasal administration and its potential active components in vivo

Ethnopharmacological relevanceDaChuanXiongFang was a well-known formula originated from Jin Dynasty, China. It has been used in both China and Japan to treat migraine. In the present study, the analgesic and sedative efficacy of DaChuanXiongFang ethanol extract (DCXFEE) after intranasal administration was tested and compared with that by intragastric route. Materials and methodsThree mice experimental models: acetic acid-induced writhing response test, hot-plate latent pain response test and pentobarbital-induced sleep model were used to evaluate DCXFEE activity. To further explore the in vivo potential active components of DCXFEE that contribute to the difference of activity induced by different administration route, ultra performance liquid chromatography–mass spectrometer (UPLC–MS) was utilized to analyze components in rat brain after given DCXFEE (60mg/kg). ResultsDCXFEE showed analgesic efficacy after intranasal administration (15, 30 and 60mg/kg) in acetic acid-induced writhing response in mice. While after intragastric administration, DCXFEE only showed analgesic efficacy at high dose (60mg/kg). Moreover, the analgesic potency was weaker after intragastric administration compared with that after intranasal administration at the same dose (60mg/kg). Similar results were obtained in hot-plate latent pain response test in mice. DCXFEE (60mg/kg) had no sedative effect after intranasal and intragastric administration. No components originated from DCXFEE were identified in rat brain 15min after oral administration. One major parent component ligustilide was detected in rat brain after intranasal administration. ConclusionThese data demonstrate that DCXFEE had faster onset of action as well as better analgesic efficacy after intranasal administration than that after intragastric administration. DCXFEE has no sedative activity on potentiation of pentobarbital-induced sleep in mice given by both routes. Ligustilide might represents the potential major bioactive component of DCXFEE after intranasal administration and contribute to its analgesic activity in vivo.

Effect of Viola tricolor on pentobarbital-induced sleep in mice

Traditionally, Viola tricolor has been recommended for its sedative property. However, no pharmacological studies have yet evaluated the effect of this plant on sleep. The hydro-alcoholic extract (HAE) was prepared by the extraction of the aerial parts of V. tricolor in 70% ethanol using a Soxhalet apparatus. Also, with solvent-solvent extraction, the HAE was further fractionated to water fraction (WF), ethyl acetate fraction (EAF) and N-butanol fraction (NBF). The extract (50, 75, 100, 150, 200, 300 mg/kg, ip) and its fractions (200 mg/kg, ip) were administrated to mice, 30 min before pentobarbital (30 mg/kg, ip) injection. Furthermore, the possible neurotoxicity of the plant was assessed using PC12 neuron cell line. The HAE, at 300 mg/kg, significantly prolonged (34%) duration of pentobarbital-induced sleep. Similarly, the EAF significantly increased (51%) the sleep duration. None of the HAE doses or the fractions could significantly change the sleep latency time. The sedative effect of V. tricolor accompanied with no neuron toxicity, except for very high concentrations of EAF. The results suggest that V. tricolor potentiates pentobarbital hypnosis and the main component(s) responsible for this effect is most likely found in EAF. Isolation and purification of the active compound(s) may yield novel sleep-prolonging agents.

Green and gold kiwifruit peel ethanol extracts potentiate pentobarbital-induced sleep in mice via a GABAergic mechanism

Kiwifruit is one of the most popular fruits worldwide, and it has various biological properties, including antioxidant, anti-allergic, and cardiovascular protective effects. The peel of kiwifruit, which is a by-product of processing, is a good source of flavonoids; however, its bioactivity has not been widely investigated. In this study, we evaluated the hypnotic effects of green (GRPE, Actinidia deliciosa) and gold (GOPE, Actinidia chinensis) kiwifruit peel ethanol extracts and their solvent fractions, and the possible underlying mechanisms. Oral GRPE and GOPE administration (125–1000mg/kg) produced a dose-dependent decrease in sleep latency and an increase in sleep duration in pentobarbital-treated mice. Among three different solvent fractions of GRPE and GOPE, ethyl acetate (EA) fractions had the greatest effect on sleep duration at 250mg/kg. The total flavonoid contents of solvent fractions were proportional to sleep duration. Like diazepam (a GABAA–benzodiazepine (BZD) receptor agonist), the hypnotic effects of GRPE, GOPE, and their EA fractions were fully inhibited by flumazenil (a GABAA–BZD receptor antagonist). These results suggest that potentiation effects of GRPE and GOPE on pentobarbital-induced sleep in mice may be modulated by a GABAergic mechanism.

Rhus parviflora and its biflavonoid constituent, rhusflavone, induce sleep through the positive allosteric modulation of GABAA-benzodiazepine receptors

Ethnopharmacological relevanceRhus parviflora is referred as ‘Tintidikah’ in traditional medicinal system of south Asia (Ayurveda). It is used in treatment of Vāta vikāra, a condition related to neurological complications as well as cure for stomach disorders. Materials and methodsDried and powdered fruits of R. parviflora were extracted with 80% aqueous methanol (RPME). The concentrated extract was successively partitioned with distilled water (DW), ethyl acetate (EtOAc), and n-butanol (n-BuOH). All extracts, as well as isolated biflavonoids from R. parviflora, were evaluated for their affinity to the benzodiazepine binding site of GABAA receptor. The sedative-hypnotic effects of the fractions were evaluated by measuring sleep latency and sleep duration during pentobarbital-induced sleep in mice after oral administration of the extract fractions. ResultsOral administration of RPME (125mg/kg, 250mg/kg, 500mg/kg, and 1000mg/kg) produced a dose-dependent decrease in sleep latency and an increase in sleep duration in mice treated with pentobarbital. The methanol extract produced a hypnotic effect that was fully blocked by 3H-Ro 15-1788 flumazenil (FLU). Further, among the solvent fractions, the ethyl acetate fraction exhibited significant activity. Among the isolated compounds, biflavonoids mesuaferrone B (1), rhusflavone (3), and agathisflavone (4) competitively inhibited FLU binding with a Ki of 0.280μM, 0.045μM, and 0.091μM, respectively. In addition, analysis of the sedative-hypnotic effects of rhusflavone, as well as those of the ethyl acetate, n-butanol, and distilled water fractions revealed that the modulation of both the ethyl acetate fraction and biflavonoid rhusflavone (3) are the most potent in inducing sleep. ConclusionThe presence of conjugated ketone and C6-C8″ biflavonoid linkage in rhusflavone may be responsible for BZD-site of the GABAA leading to decrease in sleep latency and increase sleep duration.

Isoliquiritigenin, a chalcone compound, is a positive allosteric modulator of GABAA receptors and shows hypnotic effects

Isoliquiritigenin (ILTG) is a chalcone compound and has valuable pharmacological properties such as antioxidant, anti-inflammatory, anticancer, and antiallergic activities. Recently, the anxiolytic effect of ILTG has been reported; however, its action mechanism and hypnotic activity have not yet been demonstrated. Therefore, we investigated the hypnotic effect and action mechanism of ILTG. ILTG significantly potentiated the pentobarbital-induced sleep in mice at doses of 25 and 50mg/kg. The hypnotic activity of ILTG was fully inhibited by flumazenil (FLU), a specific gamma-aminobutyric acid type A (GABAA)–benzodiazepine (BZD) receptor antagonist. The binding affinity of ILTG was 0.453μM and was found to be higher than that of the reference compound, diazepam (DZP, 0.012μM). ILTG (10−5M) potentiated GABA-evoked currents to 151% of the control level on isolated dorsal raphe neurons. ILTG has 65 times higher affinity for GABAA–BZD receptors than DZP, and the dissociation constant for ILTG was 4.0×10−10M. The effect of ILTG on GABA currents was blocked by 10−7M FLU and ZK-93426. These results suggest that ILTG produces hypnotic effects by positive allosteric modulation of GABAA–BZD receptors.

Phlorotannins of the edible brown seaweed Ecklonia cava Kjellman induce sleep via positive allosteric modulation of gamma-aminobutyric acid type A–benzodiazepine receptor: A novel neurological activity of seaweed polyphenols

The primary objective was to investigate whether seaweeds have hypnotic activity. Methanol extracts of 30 seaweeds were screened for their binding activity at the GABA type A–benzodiazepine (GABAA–BZD) receptor, a well-characterised molecular target for sedative–hypnotics. The most active seaweed was Ecklonia cava Kjellman (ECK). An ethanol extract of ECK (ECK-E) significantly potentiated pentobarbital-induced sleep in mice. In four solvent fractions separated from ECK-E, hypnotic activity was proportional to contents of total phenols and total phlorotannins, known as seaweed polyphenols. Major phlorotannins of the ethyl acetate (EtOAc) fraction with the highest activity were eckol, eckstolonol, dieckol, and triphlorethol-A, and their Ki (binding affinity, μM) values for [3H]-flumazenil binding were 1.070, 1.491, 3.072, and 4.419, respectively. Hypnotic effects of ECK-E and the EtOAc fraction were fully inhibited by flumazenil, a specific GABAA–BZD receptor antagonist. These results imply that phlorotannins of ECK induce sleep by positive allosteric modulation of the GABAA–BZD receptor.

Hypnotic effects and binding studies for GABAA and 5-HT2C receptors of traditional medicinal plants used in Asia for insomnia

Many medicinal plants have been used for treatment of insomnia in Asia. However, scientific evidence and precise mechanism for their sedative-hypnotic activity have not been fully investigated. Thus, we investigated the binding activity of the oriental plant extracts (mainly from Korea and Japan) to the well-known molecular targets for sleep regulation, GABA(A) and 5-HT(2C) receptors. Following the binding assay, sedative-hypnotic effects of the extracts with high affinity were examined in an animal model of sleep. Aqueous and ethanol extracts of 15 medicinal plants were tested for binding at the benzodiazepine site of GABA(A) receptor and 5-HT site of 5-HT(2C) receptor. The sedative-hypnotic effects of selected extracts were evaluated by measuring the sleep latency and sleep duration during pentobarbital-induced sleep in mice after oral administration of extracts. In the GABA(A) assay, the ethanol extracts of licorice and danshen displayed concentration-dependent, high affinity binding, whereas in the 5-HT(2C) assay, the ethanol extracts of ginseng and silk tree showed high affinity. Among these extracts we tested previously uncharacterized licorice and silk tree for hypnotic effects. We found the ethanol extracts of licorice and silk tree significantly decreased sleep latency and increased sleep duration in pentobarbital-induced sleep. We demonstrate for the first time that licorice and silk tree have the sedative-hypnotic activity possibly by modulating GABA(A) and 5-HT(2C) receptors. We propose that licorice and silk tree might be effective candidates for treatment of insomnia.

Effect of alkylpyrazine derivatives on the duration of pentobarbital-induced sleep, picrotoxicin-induced convulsion and gamma-aminobutyric acid (GABA) levels in the mouse brain.

The effect of alkylpyrazine derivatives on pentobarbital-induced sleeping time, picrotoxicin-induced convulsion and gamma-aminobutyric acid (GABA) levels in mouse brain were studied. The duration of pentobarbital-induced sleep in mice was dose-dependently increased by 2,5-dimethylpyrazine (DMP). The duration of pentobarbital-induced sleep was also increased by an administration route of intracerebroventricular injection. Sleep duration was also increased by the administration of isomers of DMP, 2-chloro-3,6-dimethylpyrazine (DMP-Cl) and 2-fluoro-3,6-dimethylpyrazine (DMP-F), but 3,6-dimethylpyrazine-2-thiol (DMP-SH) did not affect sleep duration. The interval until the appearance of picrotoxicin-induced convulsion was prolonged by DMP and DMP-Cl. Increased sleep duration was obtained by administering DMP in combination with aminooxyacetic acid (AOAA) and diazepam compared to a single injection. The interval until convulsion due to picrotoxin was also prolonged by the administration of DMP combined with diazepam and valproic acid (VPA). The interval until the appearance of bicuculline-induced convulsion was also prolonged by pretreatment with DMP. The GABA level in mouse brain was increased by the administration of AOAA, VPA, DMP and DMP-Cl. These results suggest that DMP and other derivatives may strengthen the GABAnergic system in the brain.