The ameliorating effect of oroxylin A on scopolamine-induced memory impairment in mice

GSK-3β activity in the hippocampus is required for memory retrieval

Several molecules were recently found to be important for the memory retrieval process in the hippocampus; however, the mechanisms underlying the memory retrieval remain poorly understood. GSK-3β has been implicated in the control of synaptic plasticity and memory formation. Here, we investigated the relationship between hippocampal GSK-3β activity and memory retrieval using behavioral and Western blotting methods. We found that GSK-3β was activated in the hippocampus after a retention session in the passive avoidance task. An intrahippocampal injection of the GSK-3β inhibitor, SB 216763, before the retention session blocked memory retrieval (but not reconsolidation) without affecting locomotor activity. These results suggest that GSK-3β activation would be essential for memory retrieval in the hippocampus.

Hippocampal extracellular signal-regulated kinase signaling has a role in passive avoidance memory retrieval induced by GABAA Receptor modulation in mice

Available evidence strongly suggests that the γ-aminobutyric acid type A (GABA(A)) receptor has a crucial role in memory retrieval. However, the signaling mechanisms underlying the role of GABA(A) receptor modulation in memory retrieval are unclear. We conducted one-trial passive avoidance task with pre-retention trial drug administration in the hippocampus to test the effects of GABA(A) receptor modulation on memory retrieval. We further tested the co-involvement of signaling molecules: extracellular signal-regulated kinase (ERK), Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), and cAMP responsive element-binding protein (CREB). First, we observed that the phosphorylation of hippocampal ERK was required for memory retrieval during the task. Accordingly, to investigate whether GABA(A) receptor activation or inhibition induces ERK phosphorylation during memory retrieval, drugs that target the GABA(A) receptor were administered into the hippocampus before the retention trial. Muscimol, a GABA(A) receptor agonist, and diazepam, an agonist to benzodiazepine-binding site of GABA(A) receptor, blocked retention trial-induced ERK phosphorylation and impaired memory retrieval. Furthermore, co-treatment with sub-effective dose of U0126, a mitogen-activated protein kinase inhibitor, blocked the upregulation of ERK phosphorylation and impaired memory retrieval, and bicuculline methiodide (BMI), a GABA(A) receptor antagonist, increased ERK phosphorylation induced by the retention trial and facilitated memory retrieval. Finally, the effects of BMI were blocked by the co-application of a sub-effective dose of U0126. These results suggest that GABA(A) receptor-mediated memory retrieval is closely related to ERK activity.

Comparison of intestinal absorption and disposition of structurally similar bioactive flavones in Radix Scutellariae

Radix Scutellariae is a commonly used herbal medicine. Baicalein, wogonin, and oroxylin A are three major bioactive flavones in Radix Scutellariae and share similar chemical structures. The intestinal absorption and disposition of baicalein have been systematically investigated by our group before. In this study, the intestinal absorption and disposition of wogonin and oroxylin A were further explored and compared with the profiles of baicalein to find potential structure-activity relationship. Absorptive models including Caco-2 cell monolayer model and rat in situ single-pass intestinal perfusion model as well as in vitro enzymatic kinetic study were employed in the current study. The absorption of baicalein, wogonin, and oroxylin A were favorable with wogonin showing the highest permeability based on two absorptive models. However, three flavones underwent a fast and extensive phase II metabolism. The intestinal metabolism of three flavones exhibited species difference between human and rat. Oroxylin A demonstrated the highest intrinsic clearance of glucuronidation among three flavones. The multidrug resistance proteins might be involved in the efflux of their intracellularly formed conjugated metabolites. The pathway of intestinal absorption and disposition of B, W, and OA was similar. However, the extent of permeability and metabolism was different among three flavones which might be due to the number and position of the hydroxyl group.

Pharmacological effects and pharmacokinetics properties of Radix Scutellariae and its bioactive flavones

Radix Scutellariae is the dried root of the medicinal plant Scutellariae baicalensis Georgi. It exhibits a variety of therapeutic effects and has a long history of application in traditional formulations as well as in modern herbal medications. It has been confirmed that flavonoids are the most abundant constituents and induce these therapeutic effects. Six flavones are proven to be the major bioactive flavones in Radix Scutellariae existing in the forms of aglycones (baicalein, wogonin, oroxylin A) and glycosides (baicalin, wogonoside, oroxylin A-7-glucuronide). All six flavones are pharmacologically active and show great potential in the treatment of inflammation, cancers and virus-related diseases. The current review covers the preparation of the herb Radix Scutellariae, quantification of its major bioactive ingredients, and pharmacological effects of the proposed six bioactive flavones. In addition, this review summarizes the pharmacokinetic profiles of the bioactive flavones reported so far that could be used for further improvement of their pharmacokinetic study. Moreover, due to abundant co-occurring bioactive components in Radix Scutellariae, our review further documents the pharmacokinetic interactions among them.

Effects of Scutellaria baicalensis on chronic cerebral hypoperfusion-induced memory impairments and chronic lipopolysaccharide infusion-induced memory impairments

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts of the roots of Scutellaria baicalensis Georgi (Labiatae) have been widely used to relieve fever related to bacterial infection and inflammatory diseases in traditional Korean medicine and have been reported to be effective in brain diseases. These experiments were conducted to examine the effects of oral administration of Scutellaria baicalensis extracts on the rescue of memory impairments induced by chronic cerebral hypoperfusion or chronic lipopolysaccharide (LPS) infusion. In addition, the underlying mechanisms of these effects were investigated.

MATERIALS AND METHODS

In the first experiment, chronic cerebral hypoperfusion was induced in male Wister rats by bilateral common carotid artery occlusion (BCCAo). Daily administration of Scutellaria baicalensis extracts was started on 20 day after BCCAo and given for 40 days. A Morris water maze was then used to evaluate the status of the hippocampal-dependent spatial learning and hippocampal mitogen-activated protein kinase (MAPK) signaling was examined in control rats, rats with chronic cerebral hypoperfusion, and rats with chronic cerebral hypoperfusion that was administered Scutellaria baicalensis. In the second experiment, hippocampal microglial activation was induced by chronic infusions of LPS into the fourth ventricle of Fisher-344 rat brains. Daily administration of Scutellaria baicalensis extracts was started on 7 day after the surgery of LPS infusion and given for 32 days. Spatial memory and hippocampal microglial activation was then examined in control rats with an artificial cerebrospinal fluid infusion, rats with chronic LPS infusion, and rats with chronic LPS infusion that were administered Scutellaria baicalensis.

RESULTS

Rats that received chronic cerebral hypoperfusion or chronic LPS infusion showed spatial memory impairments relative to their control rats; however, these symptoms were reduced by daily administration of Scutellaria baicalensis. Administration of Scutellaria baicalensis mitigated alterations of hippocampal MAPK signaling by chronic cerebral infusion and microglial activation by chronic LPS infusion.

CONCLUSIONS

These results indicate that Scutellaria baicalensis may possess therapeutic potential for the prevention of Alzheimer's disease and vascular dementia.

The memory-enhancing effects of Kami-ondam-tang in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Kami-ondam-tang (KOT), a traditional Chinese medicine, has been used to treat mental and neuropsychiatric disorders, including dementia. This study aimed to investigate the effects of KOT on cognition and the mechanisms underlying these effects in mice.

MATERIALS AND METHODS

Using the passive avoidance task, we investigated the effect of sub-chronic administration of KOT on the cognition of mice. We also examined the expressions of protein kinase B (Akt), cAMP response element-binding protein (CREB), brain-derived neurotrophic factor (BDNF), and doublecortin (DCX) in the hippocampal CA1 and dentate gyrus regions using immunohistochemistry and western blotting.

RESULTS

The administration of KOT (50mg/kg/day, p.o.) for 14 days significantly increased step-through latency in the passive avoidance task compared with vehicle-treated controls. Furthermore, KOT administration (50mg/kg/day, p.o.) significantly increased the expressions of phosphorylated Akt, phosphorylated CREB and BDNF in the hippocampal CA1 and dentate gyrus. In addition, KOT administration resulted in a significant increase in the number of DCX-immunopositive cells in the dentate gyrus.

CONCLUSIONS

These results suggest that KOT enhances cognitive performance through the upregulation of Akt-CREB-BDNF signaling and neurogenesis.

Bacopa monniera Attenuates Scopolamine-Induced Impairment of Spatial Memory in Mice

Scopolamine, an anticholinergic, is an attractive amnesic agent for discerning the action of candidate antiamnesic drugs. Bacopa monniera Linn (Syn. Brahmi) is one such antiamnesic agent that is frequently used in the ancient Indian medical system. We have earlier reported the reversal of diazepam-induced amnesia with B. monniera. In this study we wanted to test if scopolamine-induced impairment of spatial memory can also be ameliorated by B. monniera using water maze mouse model. The objective of study was to study the effect of B. monniera on scopolamine-induced amnesia. We employed Morris water maze scale to test the amnesic effect of scopolamine and its reversal by B. monniera. Rotarod test was conducted to screen muscle coordination activity of mice. Scopolamine significantly impaired the acquisition and retrieval of memory producing both anterograde and retrograde amnesia. Bacopa monniera extract was able to reverse both anterograde and retrograde amnesia. We propose that B. monniera's effects on cholinergic system may be helpful for developing alternative therapeutic approaches for the treatment of Alzheimer's disease.

Herbal extracts and phytochemicals: plant secondary metabolites and the enhancement of human brain function

Humans consume a wide range of foods, drugs, and dietary supplements that are derived from plants and which modify the functioning of the central nervous sytem (CNS). The psychoactive properties of these substances are attributable to the presence of plant secondary metabolites, chemicals that are not required for the immediate survival of the plant but which are synthesized to increase the fitness of the plant to survive by allowing it to interact with its environment, including pathogens and herbivorous and symbiotic insects. In many cases, the effects of these phytochemicals on the human CNS might be linked either to their ecological roles in the life of the plant or to molecular and biochemical similarities in the biology of plants and higher animals. This review assesses the current evidence for the efficacy of a range of readily available plant-based extracts and chemicals that may improve brain function and which have attracted sufficient research in this regard to reach a conclusion as to their potential effectiveness as nootropics. Many of these candidate phytochemicals/extracts can be grouped by the chemical nature of their potentially active secondary metabolite constituents into alkaloids (caffeine, nicotine), terpenes (ginkgo, ginseng, valerian, Melissa officinalis, sage), and phenolic compounds (curcumin, resveratrol, epigallocatechin-3-gallate, Hypericum perforatum, soy isoflavones). They are discussed in terms of how an increased understanding of the relationship between their ecological roles and CNS effects might further the field of natural, phytochemical drug discovery.

Identification and quantification of baicalein, wogonin, oroxylin A and their major glucuronide conjugated metabolites in rat plasma after oral administration of Radix scutellariae product

The current study aims to identify and quantify three flavones (baicalein, wogonin and oroxylin A) and their major metabolites (baicalin, wogonoside and oroxylin A-7-O-glucuronide) in rat plasma after oral administration of Radix scutellariae product. A simple HPLC/UV method has been developed to simultaneously determine the three flavones and their major metabolites in rat plasma. The chromatographic separation of the six analytes was achieved by a Thermo C(18) column with linear gradient elution of a mobile phase containing acetonitrile and 20mM sodium dihydrogen phosphate buffer (pH 4.6). All the tested analytes were detected by PDA detector at a wavelength of 320nm. The intra-day and inter-day precision for the current assay of the six analytes was within the range of -2.23% to 15.13% and -10.83% to 6.42%, respectively. All the studied analytes could be efficiently extracted from the rat plasma using HLB cartridge with extraction recoveries above 70% and were stable under different storage conditions. The developed assay method was successfully applied to the pharmacokinetic study of baicalin, wogonoside after oral administration of a commercially available Radix scutellariae containing capsule at a dose of 3.2g/kg to Sprague-Dawley rats. In addition to wogonoside, a new metabolite of wogonin has been identified using LC/MS/MS for the first time.

Oroxylin A, a flavonoid, stimulates adult neurogenesis in the hippocampal dentate gyrus region of mice

Previously, we reported the cognitive enhancing effects of oroxylin A in unimpaired mice and its memory ameliorating activity in various memory impaired mice. To elucidate the mechanism mediating the cognitive effects of oroxylin A, this study examined the consequences of oroxylin A administration on neurogenesis in the hippocampal dentate gyrus using immunostaining for 5-bromo-2-deoxyuridine (BrdU) incorporation. In addition, we determined whether the new cells adopted a neuronal or glial fate by examining the co-localization of BrdU staining with neuronal or glial markers. Administration of oroxylin A in a dose-dependent and time-dependent manner increased the number of BrdU-incorporating cells. Moreover, the percentage of BrdU-incorporating cells co-localized with neuronal markers, neuronal nuclei, was significantly increased by the oroxylin A administration. These results suggest that the increased neurogenesis induced by the administration of oroxylin A could be, at least in part, associated with its positive effects on cognitive processing.

The genus Scutellaria an ethnopharmacological and phytochemical review

Scutellaria (HUANG QIN) (Lamiaceae), which includes about 350 species commonly known as skullcaps, is widespread in Europe, the United States and East Asia. Some species are taken to clear away the heat-evil and expel superficial evils in traditional Chinese medicine (TCM). The present paper reviews the ethnopharmacology, the biological activities and the correlated chemical compounds of Scutellaria species. More than 295 compounds have been isolated, among them flavonoids and diterpenes. Studies show that Scutellaria and its active principles possess wide pharmacological actions, such as antitumor, anti-angiogenesis, hepatoprotective, antioxidant, anticonvulsant, antibacterial and antiviral activities. Currently, effective monomeric compounds or active parts have been screened for pharmacological activity from Scutellaria in vivo and in vitro. Increasing data supports application and exploitation for new drug development.

Involvement of phosphoinositide 3-kinase gamma in the neuro-inflammatory response and cognitive impairments induced by beta-amyloid 1-40 peptide in mice

Alzheimer disease (AD) is the most common form of dementia in the elderly, and the neuro-pathological hallmarks of AD include neurofibrillary tangles (NFT), and deposition of beta-amyloid (Abeta) in extracellular plaques. In addition, chronic inflammation due to recruitment of activated glial cells to amyloid plaques are an invariant component in AD, and several studies have reported that the use of non-steroidal anti-inflammatory drugs (NSAIDs) may provide a measure of protection against AD. In this report we have investigated whether phosphoinositide 3-kinase gamma (PI3Kgamma), which is important in inflammatory cell migration, plays a critical role in the neuro-inflammation, synaptic dysfunction, and cognitive deficits induced by intracerebroventricular injection of Abeta(1-40) in mice. We found that the selective inhibitor of PI3Kgamma, AS605240, was able to attenuate the Abeta(1-40)-induced accumulation of activated astrocytes and microglia in the hippocampus, and decrease immuno-staining for p-Akt and cyclooxygenase-2 (COX-2). Interestingly, Abeta(1-40) activated macrophages treated with AS605240 or another PI3Kgamma inhibitor, AS252424, displayed impaired chemotaxis in vitro, but their expression of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) was unaffected. Finally, AS605240 prevented Abeta(1-40)-induced cognitive deficits and synaptic dysfunction, but failed to modify scopolamine-induced amnesia. Our data suggests that inhibition of PI3Kgamma may represent a novel therapeutic target for treating AD patients.

Flavonoids with prolyl oligopeptidase inhibitory activity isolated from Scutellaria racemosa Pers

Prolyl oligopeptidase (POP) is a serine protease highly expressed in the brain that hydrolyses peptide bonds at the carboxyl terminal of prolyl residues. There is evidence that this enzyme participates in several functions of the central nervous system. Scutellaria racemosa Pers demonstrated significant and selective POP inhibition. Fractionation of the hydroalcoholic extract resulted in the isolation of four main constituents identified for the first time from S. racemosa Pers, the triterpenoid lupeol (1) and the flavonoids oroxylin A (5,7-dihydroxy-6-methoxyflavone, 2), hispidulin (4',5,7-trihydroxy-6-methoxyflavone, 3), and oroxyloside (oroxylin A 7-O-glucuronide, 4). Inhibitory assays indicated that 3 and 4 at a concentration of 100 microM inhibit 43 and 34% of total POP activity, respectively.

Free and Easy Wanderer Plus (FEWP), a polyherbal preparation, ameliorates PTSD-like behavior and cognitive impairments in stressed rats

Free and Easy Wanderer Plus (FEWP) is a well-known traditional Chinese medicine that has been shown to be effective in treating various mood disorders. The purpose of the present study was to determine whether FEWP could ameliorate stress-associated behavior in rats. Following the exposure to enhanced single prolonged stress (ESPS) paradigm, consisting of 2-hr constraint, 20-min forced swimming, ether-induced loss of consciousness, and an electric foot shock, animals were administered orally with FEWP (2.5, 5, or 10mg/kg daily) or vehicle for 2 weeks. Animals were then tested in the open field, elevated plus-maze, and Morris water maze. ESPS exposure resulted in pronounced anxiety-like behavior, without impairing locomotor activity, as indicated by significant decreases of time spent and number of entries into open arms in the elevated plus-maze test, and unaltered distance traveled in the open field test compared to unexposed animals. ESPS-exposed animals also displayed marked cognitive impairments, with significant increases of distance traveled and the escape latency to the underwater platform, and a striking decrease of time spent in the target quadrant with and without the removal of the platform in the water maze test. However, repeated treatment with FEWP, particularly at higher doses, reversed the aforementioned behavioral values in the elevated plus-maze and water maze tests to the levels similar to unexposed animals. These results indicate that FEWP possesses anxiolytic and cognition-improving effects and may be an effective herbal preparation for the treatment of stress-associated conditions, such as posttraumatic stress disorder (PTSD).

Contents of major bioactive flavones in proprietary traditional Chinese medicine products and reference herb of radix Scutellariae

A simple and efficient HPLC/UV method for the simultaneous determination of six bioactive flavones, namely baicalein, baicalin, wogonin, wogonoside, oroxylin A and oroxylin A-7-O-glucuronide, has been developed and applied for their content determination in reference herb and proprietary traditional Chinese medicine (PTCM) products of radix Scutellariae. The chromatographic separation was carried out on a Thermo C(18) column and linear gradient elution was employed with a mobile phase containing acetonitrile and 20 mM sodium dihydrogen phosphate buffer (pH 4.6). All the analytes were detected by PDA detector at a wavelength of 270 nm. Contents of the analytes in radix Scutellariae containing PTCM products in forms of capsule, soft capsule, tablet and dripping pill and the reference herb of radix Scutellariae were analyzed by sonicator extraction with methanol and water mixture (80:20) containing 1 mM HCl for 30 min followed by HPLC analysis. Separation of the six analytes was achieved within 25 min with good linearity (R(2)>0.99). The R.S.D. of both the intra-day and inter-day precision for all the six analytes was below 10.14%. The accuracy at different concentrations was within the range of -7.83 to 4.06%. The extraction recovery was within the range of 89.22-107.33% for all the analytes. Contents of the six flavones were found to vary significantly among different products with glycosides, such as baicalin, wogonoside and oroxylin A-7-O-glucuronide, in much greater quantity than their corresponding aglycones. In addition to baicalin (18.54+/-0.71%, w/w), the commonly used marker compound for radix Scutellariae, wogonoside (3.54+/-0.18%, w/w) and oroxylin A-7-O-glucuronide (2.84+/-0.14%, w/w) also existed in abundant amount in the reference herb. Our findings suggested that wogonoside and oroxylin A-7-O-glucuronide should also be served as the chemical markers together with baicalin for the quality control of herbs and PTCM products of radix Scutellariae.

Mangiferin ameliorates scopolamine-induced learning deficits in mice

The aim of this study was to evaluate the effects of Anemarrhena asphodeloides BUNGE (AA) on cholinergic memory deficits in mice. This agent has previously been used as an antipyretic, anti-inflammatory, anti-diabetic, and antidepressant in traditional Chinese medicine. Mangiferin was isolated from AA and showed a dose-dependent inhibition of acetylcholinesterase (AChE) activity (IC(50) value, 62.8 microM). Cholinergic dysfunction was induced in mice by administering scopolamine, and the animals were then tested using the passive avoidance test as well as the Morris water maze test. Mangiferin (20 mg/kg, p.o.) significantly reversed scopolamine-induced deficits in the passive avoidance test, and also improved escape latencies in training trials and increased swimming times in the Morris water maze test (p<0.05). Mangiferin also reduced acetylcholine and tumor necrosis factor (TNF)-alpha levels induced by scopolamine in mice brain (p<0.05) and inhibited nuclear factor (NF)-kappaB activation in scopolamine or TNF-alpha-stimulated BV-2 microglial cells. These results suggest that mangiferin can improve long-term cholinergic memory deficits by AChE inhibition or cholinergic receptor stimulation and inhibition of NF-kappaB activation.

In vitro study of the tocolytic effect of oroxylin A from Scutellaria baicalensis root

Scutellariae Radix is one of the well-known tocolytic Chinese herbs. Oroxylin A is isolated from the root of Scutellaria baicalensis. The main syndrome of preterm birth is caused by uterus contractions from excitatory factors. Administration of tocolytic agents is a strategy to prevent the occurrence of preterm births. The aim of this study was to investigate the effects of oroxylin A on contractions of uterine strips isolated from non-pregnant female Wistar rats (250~350 g). Contractions of the uterus were induced with acetylcholine (Ach) (1 μM), PGF_2α (0.1 μM), oxytocin (10^-3 U/ml), KCl (56.3 mM), tetraethylammonium (TEA; 1 and 10 mM), 4-aminopyridine (4-AP; 5 mM), glipizide (30 μM), a nitric oxide synthase (NOS) inhibitor (LNNA; 10^-3M), a β-receptor blocker (propranolol; 10 μM), and a cyclooxygenase inhibitor (indomethacin; 60 μM). The inhibitory effects of the amplitude and frequency of spontaneous contractions by oroxylin A were antagonized with Ach (IC₅₀ 22.85 μM), PGF_2α (IC₅₀27.28 μM), oxytocin (IC₅₀ 12.34 μM), TEA; 1 and 10 mM (IC₅₀ 52.73 and 76.43 μM), 4-AP (IC₅₀ 67.16 μM), and glipizide (IC₅₀27.53 μM), but oroxylin A was not influenced by Ca²⁺-free medium, LNNA, propranolol, or indomethacin. Otherwise, oroxylin A-mediated relaxation of the rat uterus might occur through opening of uterine calcium-dependent potassium channels or adenosine triphosphate potassium channel activation. This suggests that oroxylin A is the tocolytic principle constituent of Scutellariae Radix, and oroxylin A may provide a lead compound for new tocolytic drug development in the future.

Methylthioninium chloride reverses cognitive deficits induced by scopolamine: comparison with rivastigmine

RATIONALE

The cholinergic system is involved in cognition as well as in age-related cognitive decline and Alzheimer disease (AD). Cholinergic enhancers ameliorate AD symptoms and represent the main current therapy for AD. MTC (Methylthioninium chloride), an antioxidant with metabolism-enhancing properties may be a novel candidate with pro-cognitive capacities.

OBJECTIVES

This study was performed: (1) to assess the pro-cognitive efficacy of MTC and establish its dose-response; (2) to compare the efficacy of MTC with rivastigmine and (3) to determine the potential for combination therapy by co-administration of MTC and rivastigmine.

METHODS

Spatial cognition of female NMRI mice was tested in a reference memory water maze task. Subjects received intra-peritoneal injections of scopolamine (0.5 mg/kg) followed by vehicle, and/or MTC and/or rivastigmine (0.15-4 mg/kg MTC; 0.1-0.5 mg/kg rivastigmine) in mono or combination treatment.

RESULTS

Scopolamine treatment prevented spatial learning in NMRI female mice and the deficit was reversed by both rivastigmine and MTC in a dose-dependent manner. Mono-therapy with high doses of rivastigmine (>0.5 mg/kg) caused severe side effects but MTC was safe up to 4 mg/kg. Co-administration of sub-effective doses of both drugs acted synergistically in reversing learning deficits and scopolamine-induced memory impairments.

CONCLUSIONS

In our model, MTC reversed the spatial learning impairment. When combined with the ChEI rivastigmine, the effect of MTC appeared to be amplified indicating that combination therapy could potentially improve not only symptoms but also contribute beneficially to neuronal metabolism by minimising side effects at lower doses.

The effects of acute and repeated oroxylin A treatments on Abeta(25-35)-induced memory impairment in mice

Oroxylin A is a flavonoid that is found in the roots of Scutellaria baicalensis Georgi. The aim of this study was to characterize the effects of oroxylin A on the memory impairments and pathological changes induced by Abeta(25-35) peptide in mice. The ameliorating effect of oroxylin A on memory impairment was investigated using passive avoidance and Y-maze tasks and pathological changes were identified by immunostaining and western blotting. Abeta(25-35) peptide (5nmol) was administered by intracerebroventricular injection. In the acute treatment study, a single dose of oroxylin A (5mg/kg, p.o.) treated 1h before behavioral tests was found to significantly reverse Abeta(25-35)-induced cognitive impairments based on passive avoidance and Y-maze task findings (P<0.05). Moreover, these acute effects of oroxylin A were blocked by diazepam (1mg/kg, i.p.), a GABA(A)/benzodiazepine binding site agonist (P<0.05). On the other hand, our subchronic studies revealed that oroxylin A (1 or 5mg/kg/day, p.o.) for 7 days ameliorated the memory impairment induced by Abeta(25-35) peptide. Moreover, Abeta(25-35)-induced increases in GFAP (an astroglia marker) and OX-42 (a microglia marker), and increases in iNOS positive cells in the hippocampus were found to be attenuated by subchronic oroxylin A (1 or 5mg/kg/day, i.p., P<0.05). In addition, reductions in the immunoreactivity and protein level of ChAT (a cholinergic neuronal cell marker) in the CA3 hippocampal area induced by Abeta(25-35) peptide were also attenuated by oroxylin A. Furthermore, lipid peroxidation induced by Abeta(25-35) was also reduced by oroxylin A. These results suggest that the amelioration of Abeta(25-35) peptide-induced memory impairment by oroxylin A is mediated via the GABAergic neurotransmitter system after a single administration, or by reductions in Abeta(25-35) peptide-induced astrocyte and microglia activations, iNOS expression, lipid peroxidation, and increased cholinergic neurotransmission after subchronic administration.