Chiharu Kubo

Chronic stress, as well as acute stress, reduces BDNF mRNA expression in the rat hippocampus but less robustly.

Daily restraint for 3 weeks was shown to atrophy dendrites of hippocampal pyramidal neurons in rats. Brain-derived neurotrophic factor (BDNF), which maintains neuronal survival and morphology, has been shown to decrease in response to acute stress. Plasma glucocorticoid (GC) and serotonergic projections from the raphe nuclei play major roles in reducing BDNF synthesis in the hippocampus. We investigated BDNF mRNA levels there, together with plasma GC levels, GC receptors in the hippocampus/hypothalamus and 5-HT synthesizing enzyme, tryptophan hydroxylase in the raphe nuclei, in animals chronically stressed for 1-3 weeks, using in situ hybridization and immunohistochemistry. In these animals, BDNF mRNA levels were significantly decreased in the hippocampus after 6 h of restraint, but the ability of restraint to reduce BDNF synthesis seemed less robust than that seen in acute stress models. HPA axis response to stress in these animals assessed by plasma GC levels was delayed and sustained, and the GC receptor in the paraventricular hypothalamic nucleus was increased at 1 week. Tryptophan hydroxylase immunoreactivity was increased in the median raphe nucleus at 2-3 weeks. Repetitive stress-induced reduction of BDNF may partly contribute to the neuronal atrophy/death and reduction of hippocampal volume observed both in animals and humans suffering chronic stress and/or depression.

An oral introduction of intestinal bacteria prevents the development of a long-term Th2-skewed immunological memory induced by neonatal antibiotic treatment in mice

Background Recent epidemiological studies indicate that antibiotic use in infancy may be associated with an increased risk of developing atopy. Our previous work on animals demonstrated that kanamycin use during infancy promotes a shift in the Th1/Th2 balance towards a Th2‐dominant immunity.

Presynaptic serotonergic inhibition of GABAergic synaptic transmission in mechanically dissociated rat basolateral amygdala neurons

1 The basolateral amygdala (ABL) nuclei contribute to the process of anxiety. GABAergic transmission is critical in these nuclei and serotonergic inputs from dorsal raphe nuclei also significantly regulate GABA release. In mechanically dissociated rat ABL neurons, spontaneous miniature inhibitory postsynaptic currents (mIPSCs) arising from attached GABAergic presynaptic nerve terminals were recorded with the nystatin‐perforated patch method and pharmacological isolation. 2 5‐HT reversibly reduced the GABAergic mIPSC frequency without affecting the mean amplitude. The serotonergic effect was mimicked by the 5‐HT1A specific agonist 8‐OH DPAT (8‐hydroxy‐2‐(di‐n‐propylamino)tetralin) and blocked by the 5‐HT1A antagonist spiperone. 3 The GTP‐binding protein inhibitor N‐ethylmaleimide removed the serotonergic inhibition of mIPSC frequency. In either K+‐free or Ca2+‐free external solution, 5‐HT could inhibit mIPSC frequency. 4 High K+ stimulation increased mIPSC frequency and 8‐OH DPAT inhibited this increase even in the presence of Cd2+. 5 Forskolin, an activator of adenylyl cyclase (AC), significantly increased synaptic GABA release frequency. Pretreatment with forskolin prevented the serotonergic inhibition of mIPSC frequency in both the standard and high K+ external solution. 6 Ruthenium Red (RR), an agent facilitating the secretory process in a Ca2+‐independent manner, increased synaptic GABA release. 5‐HT also suppressed RR‐facilitated mIPSC frequency. 7 We conclude that 5‐HT inhibits GABAergic mIPSCs by inactivating the AC‐cAMP signal transduction pathway via a G‐protein‐coupled 5‐HT1A receptor and this intracellular pathway directly acts on the GABA‐releasing process independent of K+ and Ca2+ channels in the presynaptic nerve terminals.

Presynaptic 5-HT3 receptor-mediated modulation of synaptic GABA release in the mechanically dissociated rat amygdala neurons

1 Nystatin‐perforated patch recordings were made from mechanically dissociated basolateral amygdala neurons with preserved intact native presynaptic nerve terminals to study the mechanism of 5‐HT3 receptor‐mediated serotonergic modulation of GABAergic inhibition. 2 The specific 5‐HT3 agonist mCPBG (1 μM) rapidly facilitated the frequency of GABAergic miniature inhibitory postsynaptic currents (mIPSCs) and this facilitation desensitized within 1 min. Tropisetron (30 nM), a specific 5‐HT3 antagonist, blocked the mCPBG effect. 3 mCPBG augmented mIPSC amplitude. However, no direct postsynaptic serotonergic currents were evoked by mCPBG. Neither GABA‐evoked current amplitude nor the kinetics of individual GABAergic mIPSCs were affected by mCPBG. Therefore, the augmentation is unlikely to be due to postsynaptic effects evoked by mCPBG. At higher concentrations mCPBG produced shorter‐duration facilitation of miniature events. 4 While mCPBG increased the mIPSC frequency in calcium‐containing solution with Cd2+, this increase was absent in Ca2+‐free external solution. It appears that the Ca2+ influx through voltage‐dependent calcium channels was not as crucial as that through 5‐HT3 receptors for synaptic GABA release. 5 When two pulses of mCPBG (each 1 μM, 1 min) were given, the response to the second pulse elicited full recovery when the interval between pulses was at least 9 min. Protein kinase A (PKA) activation by 8‐Br‐cAMP (300 μM) shortened and PKA inhibition by Rp‐cAMP (100 μM) prolonged the recovery time. PKA activity did not affect the time course of fast desensitization. 6 Our results suggest that a 5‐HT3‐specific agonist acts on presynaptic nerve terminals facilitating synaptic GABA release without postsynaptic effects. The facilitation requires calcium influx through presynaptic 5‐HT3 receptors. PKA modulates the recovery process from desensitization of presynaptic 5‐HT3 receptor‐mediated regulation of synaptic GABA release.

The effects of psychological intervention on atopic dermatitis. A systematic review and meta-analysis.

Background: Psychological interventions may be valuable in atopic dermatitis. We systematically reviewed and carried out a meta-analysis of randomized controlled trials of psychological interventions. Methods: Electronic searches and manual journal searches were carried out. Two coders independently coded study designs, participants, treatments and outcome characteristics of the studies meeting the selection criteria. Results: Eight journal articles published between 1986 and 2006 were included. Eight types of intervention were tested: aromatherapy, autogenic training, brief dynamic psychotherapy, cognitive-behavioral therapy, dermatological education and cognitive-behavioral therapy, habit reversal behavioral therapy, a stress management program, and structured educational programs. Effect sizes were computed as correlation coefficient (r), and random effects models were used in the analysis. For eczema severity, the average effect size for the 8 trials including 8 interventions was –0.367 [χ2(1) = 7.452, p = 0.006; 95% CI –0.579 to –0.108]. The average effect sizes on itching intensity (5 trials with 5 interventions) and scratching (5 trials with 4 interventions) were –0.805 [χ2(1) = 4.719, p = 0.030; 95% CI –0.971 to –0.108] and –0.620 [χ2(1) = 24.24, p < 0.0001; 95% CI –0.767 to –0.410], respectively. Conclusions: Although the present meta-analysis revealed that psychological interventions had a significant ameliorating effect on eczema severity, itching intensity and scratching in atopic dermatitis patients, a definite conclusion about their effectiveness seems premature. Accordingly, future studies should involve more sophisticated methodologies, use established measures of outcome variables, adjust for possible confounders between the intervention and control groups, and provide sufficient data to calculate the effect sizes for future meta-analyses.

Restraint stress-induced immunosuppression by inhibiting leukocyte migration and Th1 cytokine expression during the intraperitoneal infection of Listeria monocytogenes

In this study, a murine model of Listeria monocytogenes infection was used to investigate effects of restraint stress (RST) on host defense. We observed that the L. monocytogenes infection as well as RST induced an elevation of endogenous corticosterone (CORT) levels and RST synergistically enhanced endogenous CORT levels during the listerial infection. RST suppressed the migration of leukocytes including macrophages, neutrophils, NK cells and lymphocytes into the peritoneal cavities after the intraperitoneal inoculation of L. monocytogenes. RST also suppressed the increase of the surface MHC class II antigen expression in both peritoneal macrophages and B cells during the listerial infection. Interestingly, gene expression of iNOS, MCP-1 (JE) and Th1-type cytokines including IFN-gamma and IL-12 was down-regulated but Th2-type cytokine (IL-4 and IL-6) gene expression in the PEC was rather up-regulated on day 7 after infection, indicating that Th2-type immune response is more resistant to the elevated endogenous CORT levels than Th1-type response. Treatment of mice with RU486, a glucocorticoid receptor antagonist, restored the immune responses suppressed by RST to their normal levels in the infected mice, suggesting that the RST-induced elevation of endogenous corticosterone levels is mainly responsible for the induction of the immunosuppressive events during L. monocytogenes infection.

Restraint stress elevates the plasma interleukin-6 levels in germ-free mice.

Several recent reports demonstrated that restraint stress elevates plasma IL-6 levels; however, the precise mechanism whereby stress stimuli trigger the production of IL-6 remains to be clarified. In this study, in order to elucidate whether or not the intestinal microflora contribute to the stress-induced IL-6 elevation, the plasma IL-6 response of germ-free (GF) mice, which are indeed devoid of indigenous microflora, was compared to that of specific pathogen-free (SPF) mice. The plasma IL-6 level increased after 1 h of restraint stress and thereafter gradually decreased in GF mice as well as in SPF mice. In addition, such a stress-induced IL-6 elevation was also found in the mice reconstituted with SPF feces. The expression levels of IL-6 mRNA in the liver increased after 1 h of stress in both GF and SPF mice based on the findings of a semiquantitative RT-PCR method, although no such increase was observed in the spleen and kidney of both groups of mice. These results thus indicate that restraint stress is capable of elevating the plasma IL-6 levels independently of the intestinal microflora and the liver is one of the main sources responsible for the increased plasma IL-6 during stress.

Role of interleukin 15 in colitis induced by dextran sulphate sodium in mice

Background and aims: Interleukin (IL)-15 is a member of the IL-2 family, stimulating dendritic cells, natural killer (NK) cells, NK T cells and memory CD8+ T cells. IL-15 levels were elevated in the intestinal mucosa of inflammatory bowel diseases. Here we investigated the involvement of IL-15 in the pathogenesis of acute and chronic dextran sulphate sodium (DSS) induced colitis. Methods: IL-15 knockout (KO) mice and control C57BL/6 mice were used to induce colitis with DSS in their drinking water. Survival rate, clinical activity of diseases, extent of tissue damage, leucocyte population, and cytokine production of lamina propria (LP) cells of the large intestines were assessed. Results: IL-15 KO mice exhibited resistance to DSS induced acute colitis, as reflected by lower lethality, weight loss, clinical scores, and histological scores compared with those in control mice (p<0.05). The proportions of CD44high CD8+ T cells and NK cells in LP cells and levels of interferon (IFN)-γ, tumour necrosis factor (TNF)-α, and IL-12p40 in culture supernatants of LP cells were reduced in IL-15 KO mice (p<0.05). In vivo depletion of CD8+ T cells and NK cells decreased levels of IFN-γ, TNF-α, and IL-12p40 in culture supernatants of LP cells in C57BL/6 mice (p<0.01). In chronic colitis, weight loss and clinical scores were improved and levels of IFN-γ, TNF-α, and IL-12p40 in culture supernatants of LP cells were also reduced in IL-15 KO mice (p<0.05). Conclusions: IL-15 plays an important role in the pathogenesis of both acute and chronic colitis induced by DSS in mice.

α2‐Adrenoceptor‐mediated potassium currents in acutely dissociated rat locus coeruleus neurones

1 The noradrenaline (NA)‐activated response was investigated in neurones acutely dissociated from the rat locus coeruleus (LC) using nystatin‐perforated, conventional whole‐cell and inside‐out patch recording modes under current‐ and voltage‐clamp conditions. 2 Under current‐clamp conditions, NA hyperpolarized the LC neurones, abolishing the spontaneous action potentials. In voltage‐clamp studies, NA induced an inwardly rectifying K+ current (INA) in a concentration‐dependent manner with a half‐maximum effective concentration of 2.2 × 10−7 M. 3 I NA was mimicked by the α2‐agonist UK14304 but was inhibited by either the α2B/α2C antagonist ARC239 or the α1‐ and α2B/α2C antagonist prazosin, suggesting the contribution of α2B/α2C adrenoceptors. 4 I NA was inhibited by the intracellular application of GDPβS but fully activated by intracellular perfusion of GTPγS. 5 In the inside‐out recording mode, the application of GTP to the cytoplasmic side of the patch membrane markedly enhanced the open probability of the NA‐activated single channels which represented the inwardly rectifying properties. 6 These results indicate that the activation of α2B/α2C adrenoceptors coupled with GTP‐binding protein directly activates the inwardly rectifying K+ currents in rat LC neurones, thus resulting in a decrease in the spontaneous firing activities.

Age and gender effect on alexithymia in large, Japanese community and clinical samples: a cross-validation study of the Toronto Alexithymia Scale (TAS-20)

BackgroundThe construct validity of alexithymia and its assessment using the 20-item Toronto Alexithymia Scale (TAS-20) in Japan is unknown. Low reliability has been found for the third factor of the TAS-20 in some cultures, and the factor structure for psychosomatic disorder patients has not been adequately investigated. Although alexithymia most likely has certain developmental aspects, this has infrequently been investigated.MethodsThe newly-developed Japanese TAS-20 was administered to a normative sample (n = 2,718; 14–84 y.o.), along with the NEO Five-Factor Inventory (NEO-FFI) for cross validation. Psychosomatic patients (n = 1,924, 12–87 y.o.) were tested to evaluate the factor structure in a clinical sample. College students (n = 196) were used for a test-retest study. Internal reliability and consistency were assessed, and the factorial structure was evaluated using confirmatory and exploratory factor analyses for both the normative and the clinical samples. The correlations between the TAS-20 and the NEO-FFI factor scores were evaluated. Age-related and gender differences in the TAS-20 were explored using analysis of variance in the normative sample.ResultsThe original three-factor model of the TAS-20 was confirmed to be valid for these Japanese samples, although a 4-factor solution that included negatively keyed items (NKI) as an additional factor was more effective. Significant correlations of the TAS-20 with the NEO-FFI were found, as has been previously reported. Factor analyses of the normative and patient samples showed similar patterns. The TAS-20 total, difficulty in identifying feelings (DIF), and difficulty in describing feelings (DDF) scores were high for teenagers, decreased with age, and from 30s did not change significantly. In contrast, externally oriented thinking (EOT) scores showed an almost linear positive correlation with age. DIF scores were higher for females, while EOT scores were higher for males, without any interaction between gender and age differences.ConclusionThe original three-factor concept of the TAS-20 was generally supported for practical use. Age-related differences in TAS-20 scores indicate developmental aspects of alexithymia. Alexithymia is made up of two components with different developmental paths: DIF/DDF and EOT.