Alpinia japonica extract induces apoptosis of hepatocellular carcinoma cells through G0/G1 cell cycle arrest and activation of JNK.

Hepatic cancer was the third most prevalent cause of cancer-related death worldwide in 2018, and its incidence is increasing. While therapeutic agents for hepatic cancer have improved, these agents can cause serious side effects, including damage to healthy tissues. To overcome this limitation, more than 3,000 plants have been used globally as common alternatives for cancer treatment. The anti-cancer activity of Alpinia japonica, one of the traditional herbal medicines (Korean name: Kkot-yang-ha), was investigated. Water extract of A. japonica (AJ) decreased the cell viability of hepatic cancer cells. AJ extract showed greater than 70% loss of mitochondrial potential in HepG2 cells as demonstrated by JC-1 staining. Apoptosis was induced by treatment with AJ extract as shown through FACS analysis, and G0/G1 phase arrest of 76.66% HepG2 cells was confirmed through cell cycle analysis and quantitative RT-PCR. Improper regulation of ERK1/2 might contribute to cell death, and JNK activation is necessary for apoptosis induced by stress stimuli. AJ extract stimulated the phosphorylation of JNK and ERK1/2, mitogen-activated protein kinases (MAPKs), in HepG2 cells. AJ extract has anticancer activity by inhibiting cell cycle progression, leading to apoptosis of hepatic cancer cells. This extract could potentially be used as a therapeutic agent for hepatic cancer.

Anti-Candida Potential of Sclareol in Inhibiting Growth, Biofilm Formation, and Yeast-Hyphal Transition.

Even though Candida albicans commonly colonizes on most mucosal surfaces including the vaginal and gastrointestinal tract, it can cause candidiasis as an opportunistic infectious fungus. The emergence of resistant Candida strains and the toxicity of anti-fungal agents have encouraged the development of new classes of potential anti-fungal agents. Sclareol, a labdane-type diterpene, showed anti-Candida activity with a minimum inhibitory concentration of 50 µg/mL in 24 h based on a microdilution anti-fungal susceptibility test. Cell membrane permeability with propidium iodide staining and mitochondrial membrane potential with JC-1 staining were increased in C. albicans by treatment of sclareol. Sclareol also suppressed the hyphal formation of C. albicans in both liquid and solid media, and reduced biofilm formation. Taken together, sclareol induces an apoptosis-like cell death against Candida spp. and suppressed biofilm and hyphal formation in C. albicans. Sclareol is of high interest as a novel anti-fungal agent and anti-virulence factor.

Trichosanthes kirilowii Extract Promotes Wound Healing through the Phosphorylation of ERK1/2 in Keratinocytes.

The proliferation of keratinocytes is one of the important steps in the wound-healing process, which is regulated by various signals. Prior studies have shown that Trichosanthes kirilowii extract has the ability to promote angiogenesis. Therefore, in this study, we tested the wound-healing efficacy of Trichosanthes kirilowii extract with respect to promoting keratinocyte proliferation. A total of 100 µg/mL of Trichosanthes kirilowii extract treatment improved 145.38% of keratinocyte proliferation compared with DMSO-treated control in an MTT assay and increased 238.2% of wound closure by re-epithelialization in an in vitro wound-healing assay. Trichosanthes kirilowii extract promoted ERK1/2 phosphorylation in western blot analysis and induced the expression of the c-fos and c-jun (AP-1 transcription factors), cyclins (cell cycle regulator), and growth factors CTGF and VEGF (stimulator of angiogenesis) in qRT-PCR analysis. An in vivo wound-healing assay showed that Trichosanthes kirilowii extract improved wound healing, and the significant difference in wound closure compared with DMSO-treated control was shown on days 6 and 7 with a mouse model. Taken together, we demonstrate that Trichosanthes kirilowii extract promotes the proliferation of keratinocytes by activating ERK1/2 and increasing the mRNA expression of c-fos, c-jun, CTGF, and VEGF. Therefore, we suggest Trichosanthes kirilowii extract as a new component for skin care and as a wound-healing substance.

Utilizing Red Spotted Apollo Butterfly Transcriptome to Identify Antimicrobial Peptide Candidates against Porphyromonas gingivalis.

Classical antibiotics are the foremost treatment strategy against microbial infections. Overuse of this has led to the evolution of antimicrobial resistance. Antimicrobial peptides (AMPs) are natural defense elements present across many species including humans, insects, bacteria, and plants. Insect AMPs are our area of interest, because of their stronger abilities in host defense. We have deciphered AMPs from an endangered species Parnassius bremeri, commonly known as the red spotted apollo butterfly. It belongs to the second largest insect order Lepidoptera, comprised of butterflies and moths, and lives in the high altitudes of Russia, China, and Korea. We aimed at identifying the AMPs from the larvae stages. The rationale of choosing this stage is that the P. bremeri larvae development occurs at extremely low temperature conditions, which might serve as external stimuli for AMP production. RNA was isolated from larvae (L1 to L5) instar stages and subjected to next generation sequencing. The transcriptomes obtained were curated in in-silico pipelines. The peptides obtained were screened for requisite AMP physicochemical properties and in vitro antimicrobial activity. With the sequential screening and validation, we obtained fifteen candidate AMPs. One peptide TPS-032 showed promising antimicrobial activity against Porphyromonas gingivalis, a primary causative organism of periodontitis.

Antifungal Activity of 1,4-Dialkoxynaphthalen-2-Acyl Imidazolium Salts by Inducing Apoptosis of Pathogenic Candida spp.

Even though Candida spp. are staying commonly on human skin, it is also an opportunistic pathogenic fungus that can cause candidiasis. The emergence of resistant Candida strains and the toxicity of antifungal agents have encouraged the development of new classes of potent antifungal agents. Novel naphthalen-2-acyl imidazolium salts (NAIMSs), especially 1,4-dialkoxy-NAIMS from 1,4-dihydroxynaphthalene, were prepared and evaluated for antifungal activity. Those derivatives showed prominent anti-Candida activity with a minimum inhibitory concentration (MIC) of 3.125 to 6.26 µg/mL in 24 h based on microdilution antifungal susceptibility test. Among the tested compounds, NAIMS 7c showed strongest antifungal activity with 3.125 µg/mL MIC value compared with miconazole which showed 12.5 µg/mL MIC value against Candida spp., and more importantly >100 µg/mL MIC value against C. auris. The production of reactive oxygen species (ROS) was increased and JC-1 staining showed the loss of mitochondrial membrane potential in C. albicans by treatment with NAIMS 7c. The increased release of ultraviolet (UV) absorbing materials suggested that NAIMS 7c could cause cell busting. The expression of apoptosis-related genes was induced in C. albicans by NAIMS 7c treatment. Taken together, the synthetic NAIMSs are of high interest as novel antifungal agents given further in vivo examination.

Analgesic Effects of Cnidium officinale Extracts on Postoperative, Neuropathic, and Menopausal Pain in Rat Models.

Cnidium officinale, widely cultivated in East Asia, has been reported to exhibit pharmacological efficacy in various disorders. However, little has been reported on its role as a pain killer. In this study, we reveal that the C. officinale extract (COE) has great efficacy as a novel analgesic in various in vivo pain models. Administration of COE attenuated hypersensitivity in all postoperative, neuropathic, and menopausal pain models. Decreased hyperalgesia was confirmed by a mechanical withdrawal threshold assay and ultrasonic vocalization call analysis. In addition, application of COE inhibited the induction of the proinflammatory cytokines and calpain-3 on dorsal root ganglion neurons in a spared nerve injury rat model. Treatment with ferulic acid, which was identified as one of the components of COE by HPLC analysis, alleviated nociceptive behaviors. Our findings suggest that ferulic acid is an active compound from COE, and COE is a potential phytomedical source for pain relief by inhibiting the process of inflammation.

Antihyperalgesic effects of ashwagandha (Withania somnifera root extract) in rat models of postoperative and neuropathic pain.

The root of Withania somnifera, commonly known as ashwagandha, is a traditional herb in the Indian Ayurvedic system of medicine and is used as a tonic. Here, we investigated whether W. somnifera root extract exhibits analgesic effects in plantar incision (PI) and spared nerve injury (SNI) rat models. Mechanical withdrawal threshold (MWT) was measured by von Frey filaments, and pain-related behavior was determined after operation by ultrasonic vocalization (USV) measurements. Indeed, we examined interferon-γ (IFN-γ) and interleukin-10 (IL-10) levels in the isolated dorsal root ganglia (DRG) following SNI in rats using an ELISA cytokine assay. MWT significantly increased 6 and 24 h after PI in rats receiving W. somnifera root extracts (100 and 300 mg/kg). Furthermore, the number of 22-27-kHz USV, which are a distress response, was significantly reduced at 6 and 24 h after PI in W. somnifera-treated rats (100 and 300 mg/kg). SNI-induced hyperalgesia and cytokine levels were significantly alleviated after treating with W. somnifera root extracts (100 and 300 mg/kg) for 15 continuous days. The main active compound, withaferin A, from the W. somnifera root extract has shown the CC chemokine family Receptor 2 (CCR2) antagonistic effects on monocyte chemoattractant protein-1 (MCP-1)-induced Ca2+ response in CCR2 stable cell line. These results indicate that W. somnifera root extract has a potential analgesic effect in rat models for both postoperative and neuropathic pain and shows potential as a drug or supplement for the treatment of pain.

Comparative structural study of the zona radiata of the eggs of three Gobiobotia (Cyprinidae, Teleostei), endemic Korean freshwaters.

The genus Gobiobotia in Korea has only three species and all are endemic benthic freshwater fishes. Their oocytes were observed by light microscopy, scanning electron microscopy and transmission electron microscopy to investigate the characteristics of the zona radiata (ZR), a non-cellular envelope, which surrounds the egg. Various developmental cells appeared during the spawning season. During the yolk vesicles stage, which yolk vesicles are spherically developed in periphery of the cytoplasm and gradually increase in its number and size, the ZR becomes visible between its follicular layer and ooplasm. The morphological appearance of the ZR of each of the three species was unique: G. brevibarba had a ZR with villous structures, whereas that of G. macrocephala was honeycomb-like with porous structures. In contrast, G. naktongensis had a ZR with no structural modifications during oogenesis. Such differences in the same genus are not common. These results indicate that the structure of the ZR is a useful character for identification of the genus Gobiobotia and may reflect the types of microhabitats they inhabit.

Analgesic Effect of Indian Gooseberry (Emblica officinalis Fruit) Extracts on Postoperative and Neuropathic Pain in Rats.

Indian gooseberry (Emblica officinalis fruit), also known as "Amla" is one of the oldest edible fruits known in India. It has also traditionally been used to treat inflammation, and as an analgesic to treat wounds. However, experimental evidence for the analgesic effects of E. officinalis has been lacking. The present study investigated whether E. officinalis extracts exhibit analgesic effects in the plantar incision (PI) and spared nerve injury (SNI) pain-model rats. We evaluated the mechanical withdrawal threshold (MWT) using von Frey filaments, and pain-related behavior was determined after surgery based on ultrasonic vocalization (USV). The group treated with E. officinalis extracts at 300 mg/kg had significantly increased MWT values at 6 h and 24 h after the PI, and had a significantly reduced number of 22-27-kHz USVs at 6 h and 24 h after PI. Moreover, after 15 days of continuous treatment with E. officinalis extracts, the treated group showed significantly alleviated SNI-induced hypersensitivity and reduced pro-inflammatory cytokine levels. Thus, E. officinalis extracts have potential analgesic effects in both postoperative and neuropathic pain models in vivo.

Regulation of the pacemaker activities in cultured interstitial cells of Cajal by Citrus unshiu peel extracts.

The Citrus unshiu peel has been widely used for the treatment of gastrointestinal (GI) disorders in Eastern traditional medicine. The present study aimed to investigate the effects of Citrus unshiu peel extract (CPE) on the pacemaker activity of the GI tract in cultured interstitial cells of Cajal (ICCs) derived from the mouse small intestine. The whole­cell patch­clamp configuration was used to record pacemaker potentials. In current clamp mode, exposure to CPE caused membrane pacemaker depolarization in a concentration­dependent manner. In the presence of the muscarinic M2 receptor antagonist, methoctramine, CPE induced membrane pacemaker depolarization, whereas treatment with the muscarinic M3 receptor antagonist, 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide, inhibited CPE­induced responses. When the pipette solution contained guanosine 5'-(ß-thio) diphosphate trilithium salt (1 mM), CPE marginally induced membrane pacemaker depolarization. In addition, CPE­induced membrane pacemaker depolarization was inhibited following exposure to the active phospholipase C (PLC) inhibitor U­73122, but not the inactive PLC inhibitor U­73343. In the presence of a p42/p44 mitogen­activated protein kinase (MAPK) inhibitor (PD98059), a p38 MAPK inhibitor (SB203580) or a c­jun NH2­terminal kinase (JNK) II inhibitor, CPE failed to induce membrane pacemaker depolarization. These results suggest that CPE may affect GI motility through modulating ICC pacemaker activity by activating the muscarinic M3 receptor and inducing the G­protein dependent PLC and MAPK signaling pathways.

BST2 Mediates Osteoblast Differentiation via the BMP2 Signaling Pathway in Human Alveolar-Derived Bone Marrow Stromal Cells.

The molecular mechanisms controlling the differentiation of bone marrow stromal stem cells into osteoblasts remain largely unknown. In this study, we investigated whether bone marrow stromal antigen 2 (BST2) influences differentiation toward the osteoblasts lineage. BST2 mRNA expression in human alveolar-derived bone marrow stromal cells (hAD-BMSCs) increased during differentiation into osteoblasts. hAD-BMSCs differentiation into osteoblasts and the mRNA expression of the bone-specific markers alkaline phosphatase, collagen type α 1, bone sialoprotein, osteocalcin, and osterix were reduced by BST2 knockdown using siRNA. Furthermore, BST2 knockdown in hAD-BMSCs resulted in decreased RUNX2 mRNA and protein expression. We hypothesized that BST2 is involved in differentiation of into osteoblasts via the BMP2 signaling pathway. Accordingly, we evaluated the mRNA expression levels of BMP2, BMP receptors (BMPR1 and 2), and the downstream signaling molecules SMAD1, SMAD4, and p-SMAD1/5/8 in BST2 knockdown cells. BMP2 expression following the induction of differentiation was significantly lower in BST2 knockdown cells than in cells treated with a non-targeting control siRNA. Similar results were found for the knockdown of the BMP2 receptor- BMPR1A. We also identified significantly lower expression of SMAD1, SMAD4, and p-SMAD1/5/8 in the BST2 knockdown cells than control cells. Our data provide the first evidence that BST2 is involved in the osteogenic differentiation of bone marrow stromal cells via the regulation of the BMP2 signaling pathway.

Analgesic Effect of Ilex paraguariensis Extract on Postoperative and Neuropathic Pain in Rats.

Ilex paraguariensis, known as "Yerba Mate," is an herb used in a beverage that is widely consumed in southern Latin American countries. Furthermore, it has been traditionally used to treat depression, and as an analgesic to manage both nerve pain and headache. The pain-related experimental evidence regarding the analgesic effects of Mate is unclear. Therefore, this study was designed to investigate whether Mate extract exhibits analgesic effects in both the plantar incision and spared nerve injury (SNI) models in rats. We tested the mechanical withdrawal threshold (MWT) using von Frey filaments. We also tested pain-related behavior using ultrasonic vocalization (USV). Neuropeptide Y (NPY) and pain-related cytokines were also determined in the dorsal root ganglia in a rat model of SNI. Our results showed that oral administration of Mate extract significantly increased MWT values, and reduced the number of 22-27 kHz USVs 24 h after the plantar incision operation. Moreover, after 15 d of continuous treatment with Mate extract, the SNI-induced hypersensitivity, cytokine levels, and NPY expression were significantly reduced compared to the corresponding findings in the control group. These results suggest that the intake of Mate extract has potential as a treatment for both postoperative pain and neuropathic pain.

The edible brown seaweed Ecklonia cava reduces hypersensitivity in postoperative and neuropathic pain models in rats.

The current study was designed to investigate whether edible brown seaweed Ecklonia cava extracts exhibits analgesic effects in plantar incision and spared nerve injury (SNI) rats. To evaluate pain-related behavior, we performed the mechanical withdrawal threshold (MWT) and thermal hypersensitivity tests measured by von Frey filaments and a hot/cold plate analgesia meter. Pain-related behavior was also determined through analysis of ultrasonic vocalization. The results of experiments showed MWT values of the group that was treated with E. cava extracts by 300 mg/kg significantly increased; on the contrary, number of ultrasonic distress vocalization of the treated group was reduced at 6 h and 24 h after plantar incision operation (62.8%, p < 0.05). Moreover, E. cava 300 mg/kg treated group increased the paw withdrawal latency in hot-and cold-plate tests in the plantar incision rats. After 15 days of continuous treatment with E. cava extracts at 300 mg/kg, the treated group showed significantly alleviated SNI-induced hypersensitivity response by MWT compared with the control group. In conclusion, these results suggest that E. cava extracts have potential analgesic effects in the case of postoperative pain and neuropathic pain in rats.

Analgesic effect of Harpagophytum procumbens on postoperative and neuropathic pain in rats.

Harpagophytum procumbens, also known as Devil's Claw, has historically been used to treat a wide range of conditions, including pain and arthritis. The study was designed to investigate whether H. procumbens extracts exhibit analgesic effects in plantar incision and spared nerve injury (SNI) rats. The whole procedure was performed on male SD rats. To evaluate pain-related behavior, we performed the mechanical withdrawal threshold (MWT) test measured by von Frey filaments. Pain-related behavior was also determined through analysis of ultrasonic vocalization (USVs). The results of experiments showed MWT values of the group that was treated with 300 mg/kg H. procumbens extract increased significantly; on the contrary, the number of 22-27 kHz USVs of the treated group was reduced at 6 h and 24 h after plantar incision operation. After 21 days of continuous treatment with H. procumbens extracts at 300 mg/kg, the treated group showed significantly alleviated SNI-induced hypersensitivity responses by MWT, compared with the control group. These results suggest that H. procumbens extracts have potential analgesic effects in the case of acute postoperative pain and chronic neuropathic pain in rats.

Effects of dietary isoflavones from Puerariae radix on lipid and bone metabolism in ovariectomized rats.

Puerariae radix, the dried root of Pueraria lobata Ohwi, is one of the earliest and most important edible crude herbs used for various medical purposes in oriental medicine. This study evaluated the metabolic effects of total isoflavones from P. lobata (PTIF) in ovariectomized (OVX) rats. The OVX rats were divided into four groups treated with distilled water, 17ß-estradiol (E2 10 µg/kg, once daily, i.p.) and PTIF (30 and 100 mg/kg, once daily, p.o.) for eight weeks. The treatments with high-dose PTIF significantly decreased the bone mineral density (BMD) loss in the femur and inhibited the increase in body weight and lipoprotein levels compared to the OVX-control group without elevating the serum levels of the liver enzymes, aspartate aminotransferase (AST) and alanine transaminase (ALT). Furthermore, PTIF exhibits a hepatoprotective effect in OVX-induced hepatic steatosis, indicated with reduced hepatic lipid contents. Taken together, our findings suggest that PTIF may be useful for controlling lipid and bone metabolism, at least in OVX rats. Further research is necessary to determine whether PTIF will have the same effects in humans.

Preventive effects of Eleutherococcus senticosus bark extract in OVX-induced osteoporosis in rats.

Eleutherococcus senticosus (Siberian ginseng), has been used as a powerful tonic herb with an impressive range of health benefits. This medicinal herb has been commonly used to treat bone metabolism diseases due to its traditional Korean medicine use to strengthen muscle and bone. This study was conducted to investigate prevention of bone loss by a standardized extract of dried E. senticosus stem bark in an ovariectomized (OVX) rat model of osteoporosis. The OVX groups were divided into five groups treated with distilled water, 17ß-estradiol (E2 10 µg/kg, once daily, i.p) and dried stem bark of E. senticosus extracts (DES 10, 30, and 100 mg/kg, once daily, p.o) for eight weeks, respectively. After eight weeks of treatments, the femur bone mineral density of the 100 mg/kg DES-treated group was significantly higher than that of the OVX-control group (16.7%, p < 0.01) without affecting the body, organs, and uterus weights, and serum estradiol levels. Additionally, bone markers such as serum ALP, CTx, and OC levels were significantly decreased in the DES 100 mg/kg treated group. These results show that DES is able to prevent OVX-induced in bone loss without the influence of hormones such as estrogen.

Neuroprotective effect of HT008-1, a prescription of traditional Korean medicine, on transient focal cerebral ischemia model in rats.

HT008-1 is one of the prescriptions used in Traditional Korean Medicine for the treatment of mental and physical weakness. It is composed of Panax ginseng, Acanthopanax senticosus, Angelica sinensis and Scutellaria baicalensis, which have been reported to have various pharmacological effects on the central nervous system. The study investigated whether HT008-1 has neuroprotective effects in a focal cerebral ischemia rat model. Stroke was induced in rats by 2 h of middle cerebral artery occlusion (MCAo) followed by 22 h of reperfusion. HT008-1 (30, 100 and 300 mg/kg) and the component herbs (300 mg/kg) were administered orally twice at 0 and 2 h after ischemia. Oral administration of 300 mg/kg HT008-1 reduced brain infarction by 45.7%, prolonged the latency time by 24.8% in the rotarod test, and enhanced the score by 17.0% in the balance beam test. Only P. ginseng and S. baicalensis showed protective effects, and HT008-1 showed a greater effect than its component herbs. HT008-1 down-regulated the COX-2 and OX-42 expression in the penumbra region. In conclusion, the results show that HT008-1 may be effective in a rat stroke model by an antiinflammatory mechanism and may improve sensory-motor function by reducing damage in the cortex and caudoputamen.

Chronic food restriction in young rats results in depression- and anxiety-like behaviors with decreased expression of serotonin reuptake transporter.

Evidence of semi-starvation is commonly found in patients with eating disorders. This study was conducted to examine the adverse effects of chronic caloric restriction in young rats, since there have been increasing incidence of eating disorders especially among young populations. Food restriction group was supplied daily with 50% of chow consumed by its ad libitum fed control group from postnatal day 28. After 5 weeks of food restriction, brain contents of serotonin (5-hydroxy-tryptamine; 5-HT) and its metabolite 5-hydroxyindol acetic acid were analyzed by high-performance liquid chromatography and mRNA expression of 5-HT reuptake transporter (5-HTT) by in situ hybridization. Plasma corticosterone levels were determined by radioimmunoassay. Behavioral assessments were performed with Porsolt swim test for depressive behavior and with elevated plus maze test for anxiety. Five weeks of food restriction markedly increased plasma level of corticosterone, and significantly decreased 5-HT turnover rates in the hippocampus and the hypothalamus. 5-HTT mRNA expression decreased in the raphe nucleus of food restricted rats compared with free fed controls. Immobility time during the swim test increased in the food restricted group, compared to the control group. Food restricted rats spent more time in the closed arms, less time in the open arms, of elevated plus maze compared with control rats. These results suggest that chronic caloric restriction in young rats may lead to the development of depressive and/or anxiety disorders, likely, in relation with dysfunction of brain 5-HT system.

Depressive behaviors and decreased expression of serotonin reuptake transporter in rats that experienced neonatal maternal separation.

This study was conducted to examine the pathophysiologic mechanisms of long-term adverse effects by neonatal maternal separation on neurobehaviors of the offspring. Sprague-Dawley pups were separated from dam daily for 180min during the first 2 weeks of life (MS) or undisturbed (NH), and subjected to behavioral sessions for ambulatory activity, forced swim, and elevated plus maze tests at 2 months of age. Serotonin reuptake transporter (5-HTT) mRNA levels in the raphe nucleus and the contents of serotonin (5-HT) and its metabolite 5-hydroxyindol acetic acid in the raphe and the hippocampus were examined as well. Ambulatory counts decreased and immobility duration in swim test increased in MS rats compared with NH rats. MS rats spent more time in the closed arms, less time in the open arms, of elevated plus maze, compared to NH rats. The hippocampal contents of 5-HT and the raphe expression of 5-HTT mRNA were decreased in MS rats compared with NH rats. These results suggest that neonatal maternal separation may result in the development of depression- and/or anxiety-like behaviors in later life, in which the long-term alterations in 5-HTergic neurotransmission may take a role.

Ovariectomy ameliorates dextromethorphan--induced memory impairment in young female rats.

We have previously found that dextromethorphan (DM), over-the-counter cough suppressant, impairs memory retention in water maze task, when it is repeatedly administrated to adolescent female rats at high doses. In this study we examined first if ovariectomy ameliorates the DM-induced memory impairment in female rats, and then whether or not the DM effect is revived by estrogen replacement in ovariectomized female rats. Female rat pups received bilateral ovariectomy or sham operation on postnatal day (PND) 21, and then intraperitoneal DM (40 mg/kg) daily during PND 28-37. Rats were subjected to the Morris water maze task from PND 38, approximately 24 h after the last DM injection. In probe trial, goal quadrant dwell time was significantly reduced by DM in the sham operated group, however, the reduction by DM did not occur in the ovariectomy group. When 17beta-estradiol was supplied to ovariectomized females during DM treatment, the goal quadrant dwell time was significantly decreased, compared to the vehicle control group. Furthermore, a major effect of estrogen replacement was found in the escape latency during the last 3 days of initial learning trials. These results suggest that ovariectomy may ameliorate the adverse effect of DM treatment on memory retention in young female rats, and that estrogen replacement may revive it, i.e. estrogen may take a major role in DM-induced memory impairment in female rats.