A microarray analysis of gnotobiotic mice indicating that microbial exposure during the neonatal period plays an essential role in immune system development.

BACKGROUND: Epidemiological studies have suggested that the encounter with commensal microorganisms during the neonatal period is essential for normal development of the host immune system. Basic research involving gnotobiotic mice has demonstrated that colonization at the age of 5 weeks is too late to reconstitute normal immune function. In this study, we examined the transcriptome profiles of the large intestine (LI), small intestine (SI), liver (LIV), and spleen (SPL) of 3 bacterial colonization models-specific pathogen-free mice (SPF), ex-germ-free mice with bacterial reconstitution at the time of delivery (0WexGF), and ex-germ-free mice with bacterial reconstitution at 5 weeks of age (5WexGF)-and compared them with those of germ-free (GF) mice. RESULTS: Hundreds of genes were affected in all tissues in each of the colonized models; however, a gene set enrichment analysis method, MetaGene Profiler (MGP), demonstrated that the specific changes of Gene Ontology (GO) categories occurred predominantly in 0WexGF LI, SPF SI, and 5WexGF SPL, respectively. MGP analysis on signal pathways revealed prominent changes in toll-like receptor (TLR)- and type 1 interferon (IFN)-signaling in LI of 0WexGF and SPF mice, but not 5WexGF mice, while 5WexGF mice showed specific changes in chemokine signaling. RT-PCR analysis of TLR-related genes showed that the expression of interferon regulatory factor 3 (Irf3), a crucial rate-limiting transcription factor in the induction of type 1 IFN, prominently decreased in 0WexGF and SPF mice but not in 5WexGF and GF mice. CONCLUSION: The present study provides important new information regarding the molecular mechanisms of the so-called "hygiene hypothesis".

Maternal stress affects postnatal growth and the pituitary expression of prolactin in mouse offspring.

Maternal stress exerts long-lasting psychiatric and somatic on offspring, which persist into adulthood. However, the effect of maternal stress on the postnatal growth of pups has not been widely reported. In this study, we found that maternal immobilization stress (IS) during lactation resulted in low body weight of male mouse offspring, which persisted after weaning. Despite free access to chow, IS induced maternal malnutrition and decreased the serum insulin-like growth factor-1 (IGF-1) levels in the mothers and in the pups. mRNA expression analysis of anterior pituitary hormones in the pups revealed that growth hormone (GH) and prolactin (PRL), but no other hormones, were decreased by IS. Expression of the pituitary transcription factor PIT1 and isoforms of PITX2, which are essential for the development and function of GH-producing somatotropes and PRL-producing lactotropes, was decreased, whereas that of PROP1, which is critical for the earlier stages of pituitary development, was unchanged. Immunohistochemistry also showed a decrease in pituitary PRL protein expression. These results suggest that stress in a postpartum mother has persistent effects on the body weight of the offspring. Reduced PRL expression in the offspring's pituitary gland may play a role in these effects.

A Kampo Medicine, Boi-ogi-to, Inhibits Obesity in Ovariectomized Rats.

In women facing menopause, end of menstrual activity is accompanied by lower levels of estrogen and gradual weight gain. Postmenopausal weight gain sounds an alarm for women's health and may lead to hyperlipidemia, a lipid increase and glucose intolerance. These phenomena are connected to lifestyle-related diseases such as hypertension, type II diabetes mellitus, arteriosclerosis and metabolic syndrome, making it essential to prevent weight gain in women. A Kampo medicine, Boi-ogi-to, is traditionally used to treat obese conditions, but the mechanism has not yet been investigated. In this experiment, we tested the antiobesity properties of Boi-ogi-to in ovariectomized rats by measuring changes of serum cytokine levels and adipocytokines in fat cells. After treatment with this extract for 6 weeks (20-week-old rats), we found that there was a significant weight decrease in rats treated with Boi-ogi-to as compared with that in the control group. Serum tumor necrosis factor (TNF)-α levels increased significantly in a dose-dependent manner. Gene expression of adipose tissue in uterus also dose dependently showed a significant increase of TNF-α levels, suggesting that secretion of TNF-α by fat cells might play a role in the ability of Boi-ogi-to to inhibit weight gain. While peroxisome proliferators-activated receptor-γ and adiponectin levels did not show a significant difference as compared with those in the control, levels of mRNA expression showed a tendency to increase dose dependently. Resistin did not show any significant change. These results suggest that Boi-ogi-to might be useful for the prevention of obesity that occurs in women with reduction of estrogen.

A new monoclonal antibody, A3B10, specific for astrocyte-lineage cells recognizes calmodulin-regulated spectrin-associated protein 1 (Camsap1).

Recent studies of adult neurogenesis of the mammalian central nervous system have suggested unexpected plasticity and complexity of neural cell ontogenesis. Redefinition and reconstitution of cell classification and lineage relationships, especially between glial and neural precursors, are an urgent and crucial concern. In the present study, we describe a new monoclonal antibody, A3B10, which was produced by immunizing mice with the membrane fraction prepared from astrocyte-enriched primary neural cell cultures. Immunohistochemistry of brain sections, including brains from glial fibrillary acidic protein (GFAP)-deficient mice and primary mixed neural cell cultures, as well as immunoblot analysis and immunoelectron microscopy, have revealed that 1) A3B10 recognizes a majority of cells in ependyma in neonatal and adult rats, 2) A3B10 stains almost all GFAP(+) cells and some S100beta(+) cells in the corpus callosum, 3) A3B10 specifically stains astrocytes in vitro in primary cultures of rat embryonic cerebral hemispheres, 4) A3B10 equally stains ependymal cells of wild-type and GFAP-deficient mice, and 5) A3B10 antigen might construct intermediate filament bundles with GFAP and/or vimentin. These data suggested that the antibody labels a wide array of astorcytic-lineage cells including astrocytes, astrocyte precursors, and neural stem cells. Screening a cDNA library derived from rat embryonic brain has revealed that the antibody recognizes calmodulin-regulated spectrin-associated protein 1 (Camsap1). Thus this antibody may provide not only a new marker to identify astrocyte-lineage cells but also a new target molecule to elucidate the ontogeny, development, and pathophysiological functions of astrocyte-lineage cells.

Orengedokuto and berberine improve indomethacin-induced small intestinal injury via adenosine.

BACKGROUND: Recent endoscopic technology has revealed that small intestinal injury is a serious threat to patients receiving nonsteroidal anti-inflammatory drugs (NSAIDs). We previously showed that Japanese herbal medicine, Orengedokuto (OGT; Huang-Lian-Jie-Du-Tang in Chinese), protects mice from lethal indomethacin (IND)-induced enteropathy. To elucidate the mechanism of the protective effect of OGT, we performed microarray analyses and high power statistical analyses of microarray data using new bioinformatics tools. METHODS: Female BALB/c mice were subcutaneously injected with IND (20 mg/kg) once a day for 2 days. OGT-treated mice received a diet containing OGT from the first IND injection until the end of the experiment. Gene expression signals of small intestine were obtained with GeneChip. Analyses for overrepresentation of Gene Ontology categories were conducted using MetaGene Profiler (MGP) and the changes were visualized by Cell Illustrator Online (CIO). Furthermore, active ingredients of OGT were investigated. RESULTS: MGP and CIO suggested a critical role for the adenosine system, especially adenosine deaminase (ADA), a key enzyme of adenosine catabolism. Quantitative real time RT-PCR and in situ hybridization showed that OGT decreased the expression of ADA, which possibly resulted in the elevation of the anti-inflammatory nucleoside adenosine. Blockade of the adenosine A2a receptor abrogated the protective effect of OGT. Berberine, a major ingredient of OGT, suppressed ADA expression and reduced the incidence of lethality. CONCLUSIONS: OGT may prevent IND-induced enteropathy by decreasing ADA which results in the elevation of adenosine. Modulation of the adenosine system may be an efficient therapeutic strategy for NSAID-induced enteropathy.

Importance of the interferon-alpha system in murine large intestine indicated by microarray analysis of commensal bacteria-induced immunological changes.

BACKGROUND: Although microbiota play a critical role in the normal development and function of host immune systems, the underlying mechanisms, especially those involved in the large intestine (LI), remain unknown. In the present study, we performed transcriptome analysis of the LI of germ-free (GF) and specific pathogen-free (SPF) mice of the IQI strain, an inbred strain established from ICR mice. RESULTS: GeneChip analysis, quantitative real-time RT-PCR, and reconfirmation using bacteria-inoculated GF mice revealed differences in the expression levels of several immune-related genes, such as cryptdin-related sequences (CRS), certain subsets of type 1 interferon (IFN)-related genes, class Ib MHC molecules, and certain complements. LI expressed no authentic cryptdins but predominantly expressed CRS2, 4, and 7. The mRNA levels of IFN-related genes, including Irf7, Isgf3g, Ifit1 and Stat1, were lower in SPF- and flora-reconstituted mice. When an oral IFN-alpha inducer tilorone analog, R11567DA, was administered to SPF mice, IFN-alpha was induced rapidly in the LI at 4 h, whereas no IFN-alpha protein was detected in the small intestine (SI) or blood. In situ hybridization and immunohistochemistry suggested that the IFN-alpha production originated from Paneth cells in the SI, and portions of lamina proprial CD11b- or mPDCA1-positive cells in the LI. CONCLUSION: The present study suggests that microbial colonization, while inducing the expression of anti-microbial peptides, results in the down-regulation of certain genes responsible for immune responses, especially for type I IFN synthesis. This may reflect the adaptation process of the immune system in the LI to prevent excessive inflammation with respect to continuous microbial exposure. Further, the repertoire of anti-microbial peptides and the extraordinary role of interferon producing cells in the LI have been found to be distinct from those in the SI.

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

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

Identification of activated transcription factors from microarray gene expression data of Kampo medicine-treated mice.

We propose an approach to identify activated transcription factors from gene expression data using a statistical test. Applying the method, we can obtain a synoptic map of transcription factor activities which helps us to easily grasp the system's behavior. As a real data analysis, we use a case-control experiment data of mice treated by a drug of Kampo medicine remedying degraded myelin sheath of nerves in central nervous system. Kampo medicine is Japanese traditional herbal medicine. Since the drug is not a single chemical compound but extracts of multiple medicinal herb, the effector sites are possibly multiple. Thus it is hard to understand the action mechanism and the system's behavior by investigating only few highly expressed individual genes. Our method gives summary for the system's behavior with various functional annotations, e.g. TFAs and gene ontology, and thus offer clues to understand it in more holistic manner.

Administration of substance P during a primary immune response amplifies the secondary immune response via a long-lasting effect on CD8+ T lymphocytes.

Atopic dermatitis can be exacerbated or induced by scratching or psychological stress; both cause the release of substance P (SP) from sensory nerves. Therefore, SP may have an etiological role in mechanisms underlying AD. Here, we show that administration of SP during the primary immune response (PIR) imprinted long-lasting pro-inflammatory immunity, resulting in exacerbation of the secondary immune response (SIR) in the absence of further SP. Five days after sensitization with dinitrofluorobenzene (DNFB), challenge with DNFB together with SP ("SP-Group") resulted in an increased PIR (as evaluated by ear swelling and granulocyte infiltration) compared to DNFB only ("Control-Group"). On day 26, after inflammation completely subsided, a second challenge with DNFB only (without SP) caused an increased SIR in the "SP-Group" compared to controls. Pretreatment on day 5 with spantide, an SP receptor antagonist, prevented increased ear swelling in the "SP-Group" not only on day 5 (PIR) but also on day 26 (SIR). In contrast, spantide treatment on day 26 did not affect the SIR. Adoptive transfer experiments suggested that CD8(+) T cells were involved in mediating enhanced SIR in animals pretreated on day 5 with SP. The present study offers a novel experimental approach to an uninvestigated facet of the pro-inflammatory effect of SP, i.e., exacerbation of inflammation via a long-term and indirect influence on CD8(+) T lymphocytes.

Effect of herbal medicine Juzentaihoto on hepatic and intestinal heat shock gene expression requires intestinal microflora in mouse.

AIM: To evaluate the role of intestinal microflora in the effects of multi-herbal medicine on gene expression in the gut and liver. METHODS: The multi-herbal medicine Juzentaihoto (JTX) was administered to five germ-free mice and regular mice for 2 wk. Among the results of the comprehensive gene chip analysis of the intestine and liver, we featured heat shock proteins (HSPs) 70 and 105 because their gene expression changed only in the presence of microflora. Real-time RT-PCR was performed to confirm the expression levels of these HSP genes. To determine whether JTX acts directly on the HSP genes, sodium arsenite (SA) was used to induce the heat shock proteins directly. To examine the change of the intestinal microflora with administration of JTX, the terminal restriction fragment polymorphism (T-RFLP) method was used. To identify the changed bacteria, DNA sequencing was performed. RESULTS: Heat shock protein gene expression, documented by gene chip and real-time RT-PCR, changed with the administration of JTX in the regular mice but not in the germ-free mice. JTX did not suppress the direct induction of the HSPs by SA. T-RFLP suggested that JTX decreased unculturable bacteria and increased Lactobacillus johnsoni. These data suggested that JTX changed the intestinal microflora which, in turn, changed HSP gene expression. CONCLUSION: Intestinal microflora affects multi-herbal product JTX on the gene expression in the gut and liver.

Endogenous glucocorticoids are essential for maintaining prefrontal cortical cognitive function.

Glucocorticoid hormones are important in the maintenance of many brain functions. Although their receptors are distributed abundantly throughout the brain, including the prefrontal cortex (PFC), it is not clear how glucocorticoid functions, particularly with regard to cognitive processing in the PFC. There is evidence of PFC cognitive deficits such as working memory impairment in several stress-related neuropsychiatric disorders, including depression, schizophrenia, and Parkinson's disease. Disruption of the hypothalamo-pituitary-adrenal (HPA) system, which is characterized by attenuated glucocorticoid negative feedback, is also observed. In rats, chronic stress induces working memory impairment as a result of decreased dopaminergic transmission in the PFC. These chronically stressed rats also show HPA disruption; this is caused in part by a reduced glucocorticoid response in the PFC. These findings implicate reduced glucocorticoid actions in working memory impairment. In the present study, we examined the effects of the suppression of endogenous glucocorticoids by adrenalectomy (ADX) on working memory in rats and explored the involvement of PFC dopaminergic activities in memory. The ADX impaired working memory, decreased dopamine release, and upregulated D1 receptors in the PFC. These dysfunctions were prevented by corticosterone replacement that reproduced normal physiological plasma levels, indicating that suppression of glucocorticoids causes these dysfunctions. Moreover, the ADX-induced working memory impairment was ameliorated by intra-PFC infusions of a D1 receptor agonist, SKF 81297. Thus, suppression of glucocorticoids impaired working memory through a D1 receptor-mediated hypodopaminergic mechanism in the PFC. This finding indicates that endogenous glucocorticoids are essential for maintaining PFC cognitive function and suggests that HPA disruption contributes to PFC cognitive deficits.

The herbal medicine Sho-saiko-to selectively inhibits CD8+ T-cell proliferation.

Sho-saiko-to (SST), a Chinese/Japanese traditional herbal medicine, has been widely used to treat chronic hepatitis in Japan, and the immunomodulatory properties of SST are likely to mediate its beneficial effect. In the present study, we examined the effects of SST and its various ingredients on the count and proliferation of T-cell subsets in cultured splenocytes and hepatic mononuclear cells. SST, wogonin-7-O-glucuronoside (a major SST ingredient), and wogonin (an intestinal metabolite of wogonin-7-O-glucuronoside) increased CD4/CD8 ratio via a decrease of CD8+ T-cell counts with no effect on CD4+ T-cell counts. Flow cytometric analyses of viability, proliferation, and cell cycle revealed that wogonin suppressed CD8+ T-cell proliferation without inducing cell death. SST and wogonin administered to mice increased the CD4/CD8 ratio in hepatic mononuclear cells but not in splenocytes. These findings suggest that SST may modulate the CD4/CD8 ratio via the selective inhibition of CD8+ T-cell proliferation by the SST ingredient wogonin-7-O-glucuronoside or its metabolite wogonin.

Effects of Byakko-ka-ninjin-to on salivary secretion and bladder function in rats.

Byakko-ka-ninjin-to (BN) is a Kampo medicine (traditional Japanese medicine) that is frequently used to treat xerostomia, which is also a side effect of anticholinergic agents such as oxybutynin and propiverine widely used for the treatment of patients with urinary incontinence or frequency. We investigated the effects of BN on salivation and bladder function in rats, in the presence and absence of oxybutynin. Treatment with BN alone resulted in a slight increase in salivary secretions. In contrast, pilocarpine, a known muscarinic agonist, produced a significant increase in salivary secretions that could be blocked by pretreatment with oxybutynin. A single oral dose of BN at 200mg/kg body weight just before oxybutynin treatment resulted in less inhibition by oxybutynin of pilocarpine-induced salivation. However, BN had no effect on the decreased amplitude of bladder contractions that result from oxybutynin administration. These results suggest that BN might be useful for the xerostomia induced by anticholinergic agents, without influencing their beneficial effect on micturition.

Eugenol exhibits antidepressant-like activity in mice and induces expression of metallothionein-III in the hippocampus.

Here we show that eugenol has an antidepressant-like activity comparable to that of imipramine using a forced swim test and a tail suspension test in mice. Furthermore, we show that both eugenol and imipramine induce brain-derived neurotrophic factor (BDNF) in the hippocampus with and without induction of metallothionein-III (MT-III), respectively. It may be possible that MT-III expression is involved in the exhibition of antidepressant-like activity of eugenol, not of imipramine.

The herbal medicine Shosaiko-to exerts different modulating effects on lung local immune responses among mouse strains.

Shosaiko-to (SST), a Chinese/Japanese traditional herbal medicine, has recently been demonstrated to increase lung interleukin-6 (IL-6) levels and to ameliorate pulmonary disorders in BALB/c mice (BALB). In the present study, we examined the effects of SST on lung cytokine levels and lipopolysaccharide (LPS)-induced lung injury in C57BL/6 mice (B6), which are known to show different immune responses from BALB due to the difference in genetic backgrounds. In B6, in contrast with BALB, SST decreased lung IL-6 levels and exacerbated LPS-induced lung injury. Investigation of the active components of SST suggested that multiple ingredients were supposed to be responsible for IL-6-attenuating activity in vivo. Further, we examined the effect of metabolites of major ingredients of SST on IL-6 production from lung immune cells in vitro. Saikogenin D and oroxylin A attenuated IL-6 production in LPS-stimulated alveolar macrophages of B6 more than in that of BALB. Liquiritigenin, which was previously reported to enhance IL-6 production in anti-CD3 monoclonal antibody-stimulated lung mononuclear cells of BALB, showed no effect on that of B6. These findings suggest that SST may have different, possibly even opposite, effects on lung immunity in hosts with different genetic backgrounds.

Saiko-ka-ryukotsu-borei-to, an herbal medicine, prevents chronic stress-induced disruption of glucocorticoid negative feedback in rats.

Exposure to stress is known to precipitate or exacerbate many neuropsychiatric disorders such as depression. Abnormality of the neuroendocrine system, as shown by increased adrenal weight and attenuated glucocorticoid negative feedback, is frequently seen in depression. The aim of the present study is to clarify the usefulness of saiko-ka-ryukotsu-borei-to, an herbal medicine, in the treatment of abnormality of the neuroendocrine system using an experimental stress-depression model. Rats were subjected to water immersion and restraint for 2 h daily for 4 weeks (chronic stress), followed by recovery for 10 days. Saiko-ka-ryukotsu-borei-to was administered during the stress and recovery periods (100, 300, or 1000 mg/kg daily, p.o.) or only during the recovery period (1000 mg/kg). After the recovery period, the adrenal weight was measured, and glucocorticoid feedback ability was evaluated by a dexamethasone suppression test using 30 microg/kg dexamethasone. The administration of saiko-ka-ryukotsu-borei-to during the stress and recovery periods prevented the stress-induced increase in adrenal weight or the attenuated negative feedback in a dose-dependent manner. The administration of saiko-ka-ryukotsu-borei-to during the recovery period alone also ameliorated the abnormality of the neuroendocrine system. These results indicate that saiko-ka-ryukotsu-borei-to is effective against chronic stress-induced abnormality of the neuroendocrine system. Because some symptoms and symptomatic relapses in depressives are attributed to dysfunction of the hypothalamo-pituitary-adrenal axis, the present findings provide information important for prevention and treatment of depression.

The herbal medicine Dai-kenchu-to and one of its active components [6]-shogaol increase intestinal blood flow in rats.

The present study investigated the effects of the herbal medicine Dai-kenchu-to (DKCT) and its 4 individual ingredients on intestinal blood flow (IBF) in rats by laser Doppler flowmetry. Intraduodenal administration of DKCT (30, 100 and 300 mg/kg) increased IBF in a dose-dependent manner, whereas the mean arterial blood pressure was not affected. One of the ingredients in DKCT is dried ginger rhizome (150 mg/kg), whose main component is [6]-shogaol (2 mg/kg), both of which showed similar effects to those shown by DKCT, while the other ingredients in DKCT only slightly increased IBF or had no effect. The calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP (8-37), completely abolished the hyperemia induced by DKCT, dried ginger rhizome and [6]-shogaol. However, the vasoactive intestinal polypeptide (VIP) receptor antagonist, [4-Cl-DPhe6, Leul7]-VIP, and atropine were less inhibitory than CGRP (8-37), and the substance P (SP) receptor antagonist, spantide, had no effect. The present study demonstrated that DKCT and one of its active components, [6]-shogaol, produced an increase in IBF which was mainly mediated by CGRP and suggests that DKCT may be useful in the treatment of intestinal ischemia-related diseases.

Saiko-ka-ryukotsu-borei-to, a herbal medicine, ameliorates chronic stress-induced depressive state in rotarod performance.

Exposure to chronic stress is thought to play an important role in the etiology of depression. This disorder has been shown to involve disruption of the hypothalamo-pituitary-adrenal (HPA) system and dysfunction of the prefrontal cortex (PFC). We have demonstrated that chronic stress in rats induces similar HPA disruption or a depressive state caused by a reduction of dopaminergic and serotonergic transmission in the PFC. We have also shown that saiko-ka-ryukotsu-borei-to, a herbal medicine, prevents such chronic stress-induced HPA disruption. However, the behavioral and neurochemical bases of this drug remain unclear. Here we examined the effects of saiko-ka-ryukotsu-borei-to on the depressive behavioral state and the reduction of transmission resulting from chronic stress. The chronic stress was induced by water immersion and restraint (2 h/day) for 4 weeks followed by recovery for 10 days. The treatment with saiko-ka-ryukotsu-borei-to (100, 300, or 1000 mg/kg p.o.) ameliorated the stress-induced depressive state in a dose-dependent manner, evaluated by a rotarod test. A microdialysis study indicated that the drug treatment significantly prevented the chronic stress-induced decreases in extracellular concentrations of dopamine and serotonin in the PFC. These results suggest that saiko-ka-ryukotsu-borei-to ameliorates the chronic stress-induced depressive state based on the prevention of PFC dysfunction. These findings provide important information for treatment of depression.

Chronic stress impairs rotarod performance in rats: implications for depressive state.

Exposure to chronic stress is thought to precipitate or exacerbate several neuropsychiatric disorders such as depression. Here, we examined the effects of chronic stress administered by water immersion and restraint (2 h/day) for 4 weeks followed by a 10-day recovery period on rotarod performance. The time course study revealed that the riding time on a rotating rod was not affected at Day 1 or Week 1 of the stress period, but was significantly decreased at Week 4 and after the 10-day recovery period. However, traction performance and locomotor activity were not changed by chronic stress. We next examined the involvement of a serotonergic mechanism in the impairment of rotarod performance. The post-stress administration of a serotonergic antidepressant, trazodone (10 mg/kg, daily for 10 days) significantly ameliorated the impairment of rotarod performance. A microdialysis study also revealed a decrease in the extracellular concentration of serotonin in the prefrontal cortex. These results indicate that chronic stress impairs the rotarod performance in a manner that is not due to muscle relaxation or motor dysfunction, and this impairment may imply a behaviorally depressive state mediated by a serotonergic mechanism. These findings provide insight into the underlying mechanisms of stress-induced neuropsychiatric disorders.

Dopamine-receptor stimulation in the prefrontal cortex ameliorates stress-induced rotarod impairment.

Exposure to chronic stress is thought to play an important role in the etiology of depression. In this disorder, dopaminergic dysfunction in the prefrontal cortex (PFC) is thought to be involved. Indeed, chronic stress reduces dopaminergic transmission in the rat PFC or induces a behaviorally depressive state. However, a relationship between the reduced dopaminergic activity and the behavior of the chronically stressed rats has not been proven. Here, we examined the effects of local application of a dopamine Type I (D(1)) receptor-specific agonist, SKF 81297, in the PFC on the chronic-stress-induced depressive state using a rotarod test. The chronic stress produced by water immersion and restraint for 4 weeks followed by recovery for 10 days impaired the rotarod performance without changing the traction performance or locomotor activity. Although intra-PFC infusion of 1 or 10 ng of SKF 81297 did not affect this impairment, 100 ng of SKF 81297 significantly ameliorated it. These results suggest that the chronic-stress-induced depressive state is caused by a D(1) receptor-mediated hypodopaminergic mechanism in the PFC. These findings will further understanding of the mechanisms underlying the pathophysiology of depression.