Biomedical subjects

Tsukasa Koyama

Publications and source records attributed to Tsukasa Koyama.

At least 19 recordsLinked to original sources

PubMed2006

Effects of calmodulin and protein kinase C modulators on transient Ca2+ increase and capacitative Ca2+ entry in human platelets: relevant to pathophysiology of bipolar disorder.

Disturbed intracellular calcium (Ca(2+)) homeostasis has been implicated in bipolar disorder, which mechanisms may be involved in the dysregulation of protein kinase C (PKC) and calmodulin systems. In this study, we investigated a transient intracellular Ca(2+) increase induced by thapsigargin, an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase pump (SERCA), and a capacitative Ca(2+) entry followed by addition of extracellular Ca(2+), in the presence or absence of PKC/calmodulin modulators in the platelets of healthy subjects in order to elucidate the role of SERCA in Ca(2+) homeostasis and to assess how both PKC and calmodulin systems regulate the two Ca(2+) responses. Moreover, we also examined the thapsigargin-elicited transient Ca(2+) increase and capacitative Ca(2+) entry in patients with mood disorders. PKC and calmodulin systems have opposite regulatory effects on the transient Ca(2+) increase and capacitative Ca(2+) entry in the platelets of normal subjects. The inhibitory effect of PKC activation on capacitative Ca(2+) entry is significantly increased and the stimulatory effect of PKC inhibition is significantly decreased in bipolar disorder compared to major depressive disorder and normal controls. These results suggest the possibility that increased PKC activity may activate the inhibitory effect of capacitative Ca(2+) entry in bipolar disorder. However, this is a preliminary study using a small sample, thus further studies are needed to examine the PKC and calmodulin modulators on the capacitative Ca(2+) entry in a larger sample.

Adult↗

PubMed2006

Left temporal perfusion associated with suspiciousness score on the Brief Psychiatric Rating Scale in schizophrenia.

We evaluated the relationship between regional cerebral blood flow (rCBF) and clinical symptoms in patients with schizophrenia. Single photon emission computed tomography with N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) was used to study 29 patients with schizophrenia. Clinical symptoms were assessed using the Brief Psychiatric Rating Scale (BPRS). We examined the correlation between rCBF and each BPRS item score using Statistical Parametric Mapping software. Corrected P-values < 0.05 were considered as statistically significant. The suspiciousness score on the BPRS was positively correlated with rCBF in the left inferior temporal gyrus. There was no significant correlation between rCBF and any other items of the BPRS. There was no significant correlation between rCBF and chlorpromazine-equivalent dosage. This analysis permits the quantitative assessment of the severity of persecutory delusions in relation to left temporal perfusion in patients with schizophrenia.

Adolescent↗

PubMed2006

Long-term outcome of antidepressant-refractory depression: the relevance of unrecognized bipolarity.

BACKGROUND: The long-term outcome of antidepressant-refractory depression is not well known. Therefore, the present study investigated the long-term outcome of 26 antidepressant-refractory patients with depression, whom we had studied and treated in 1995. METHODS: Before being classified as nonresponse, these patients had been treated adequately with at least two tricyclic or heterocyclic antidepressants (a minimum of the equivalent of 150 mg of imipramine for 4 weeks). In 1995, 21 of 26 patients were diagnosed with unipolar depression, while 5 were diagnosed with bipolar depression. Mean follow-up was 5.7 years (range: 1-7 years) and changes in diagnosis, remission and treatment efficacy were evaluated. RESULTS: Following the long-term follow-up, 13 patients achieved full remission and demonstrated high social functioning (mean GAF score, 91). A further four depressed patients experienced full remission; however, subsequent recurrence was observed. In total, 17 of 26 patients experienced remission at least once during the long-term follow-up period despite the chronic depressive episodes observed at study entry. Adjuvant treatment with lithium, dopamine receptor agonists or thyroid hormone was effective for promoting full remission. Among the 21 patients initially diagnosed with unipolar depression in 1995, diagnoses were changed to bipolar disorder in 5 cases. LIMITATIONS: This naturalistic study had a relatively small sample size and treatment was not controlled. CONCLUSIONS: Long-term follow-up revealed that a substantial proportion of antidepressant-refractory depression is comprised of bipolar disorders. In addition, augmentation therapies are effective for promoting full remission among chronically depressed patients without a risk of serious side effects.

Adult↗

PubMed2006

Effect of combined treatment with noradrenaline and serotonin reuptake inhibitors on conditioned freezing.

To clarify the therapeutic interaction between serotonin and noradrenaline reuptake inhibition on fear, this study examined the acute and subchronic effects of combined treatment with the selective serotonin reuptake inhibitor citalopram and the selective noradrenaline reuptake inhibitor reboxetine on the expression of conditioned fear (re-exposure to an environment paired previously with inescapable electric footshocks). After fear conditioning was achieved with footshocks, the drugs were administered to rats and freezing behavior, as an index of fear, was observed in the shock chamber. Acute and subchronic treatment with citalopram was reproducibly anxiolytic against conditioned freezing. Acute reboxetine worsened conditioned freezing and reversed the acute anxiolytic effects of citalopram, but this anxiogenic effect of noradrenaline reuptake inhibition was not observed after subchronic treatment. These results suggest that adding noradrenaline reuptake inhibitors to serotonin reuptake inhibitors adversely affects fear, at least with acute treatment.

Analysis of Variance↗

PubMed2006

Involvement of a polymorphism in the 5-HT2A receptor gene in impulsive behavior.

RATIONALE AND OBJECTIVE: Impulsive behavior has been suggested to occur due to a dysfunction of serotonergic 5-HT neurotransmission. After evaluation by a self-reporting measure, a polymorphism in the promoter of the 5-HT2A receptor gene has been proposed to underlie the impulsive behavior; however, this hypothesis is not convincing. In this study, we examined whether this 5-HT2A receptor gene polymorphism is involved in impulsive aggression by evaluating a behavioral task (go/no-go task) in normal volunteers. MATERIALS AND METHODS: The polymorphism of the 5-HT2A receptor gene promoter was analyzed by polymerase chain reaction using lymphocytes from 71 volunteers. Impulsivity was defined as the number of commission errors (responding when one should not) made during a go/no-go task (a larger number of commission errors indicates greater difficulty in inhibiting the behavior). RESULTS: The subjects in the group with the A-1438A allele of the 5-HT2A receptor gene (A-1438A group) made more commission errors under the punishment-reward condition in a go/no-go task than those in the G-1438G group. CONCLUSIONS: These results suggest the possible involvement of the A-1438A polymorphism of the 5-HT2A receptor gene in impulsive behavior; this was evaluated using a behavioral task measure that can directly reveal the traits of human impulsive behavior.

Adult↗

PubMed2006

Effect of carbamazepine on the single oral dose pharmacokinetics of perospirone and its active metabolite.

Perospirone is a serotonin 5-HT(2A) and dopamine D(2) receptor antagonist which originated in Japan. It has been shown that perospirone is metabolized to ID-15036 mainly by CYP3A4 based on an in vitro study. To investigate the metabolism of perospirone in humans, the authors measured the concentration of perospirone and ID-15036 after a single oral dose of perospirone (8 mg) in 10 healthy male subjects, before and during coadministration of carbamazepine, known as a potent inducer of CYP3A4. Before carbamazepine coadministration, the peak plasma concentrations+/-SD of perospirone and ID-15036 were 4.0+/-4.3 and 11.7+/-7.1 ng/ml, respectively. During carbamazepine coadministration, the concentration of perospirone was decreased below the detection limit, and that of ID-15036 was 6.0+/-1.7 ng/ml. The concentrations of perospirone and ID-15036 were influenced significantly by the treatment with carbamazepine, and this was probably attributable to the induction of CYP3A4. This study provided an in vivo evidence of involvement of CYP3A4 in the metabolism of perospirone.

Administration, Oral↗

PubMed2006

Fluvoxamine treatment of generalized social anxiety disorder in Japan: a randomized double-blind, placebo-controlled study.

The efficacy of selective serotonin reuptake inhibitors (SSRIs) for the treatment of social anxiety disorder (SAD) has been reported in the USA and Europe. However, no clinical investigation has been done with SSRIs in Japanese patients with SAD. This study was performed to determine the effectiveness and safety of fluvoxamine for generalized SAD (GSAD) in Japanese patients. In this double-blind study, patients meeting DSM-IV criteria for GSAD were randomized to receive treatment with fluvoxamine or placebo for 10 wk. Fluvoxamine treatment was initiated at 50 mg/d, and increased by 50 mg weekly to a maximum of 150 or 300 mg/d. The primary efficacy outcome was mean change from baseline on the Liebowitz Social Anxiety Scale - Japanese Version (LSAS-J) total score. The secondary outcomes were response according to the Clinical Global Impressions - Global Improvement (CGI-I) score and three domains of the Sheehan Disability Scale (SDS; used to assess psychosocial impairment). A total of 176 fluvoxamine-treated patients and 89 placebo-treated patients were eligible for the efficacy analysis. At week 10, the fluvoxamine-treated patients had a significantly greater reduction in the LSAS-J total score compared with placebo-treated patients (p=0.0197), with significantly more fluvoxamine recipients being at least much improved on the CGI-I scale compared with placebo-treated patients (p=0.024). Fluvoxamine-treated patients also had better responses on the SDS compared with placebo-treated patients (p=0.0208). Fluvoxamine was safe and well tolerated. These results suggest that fluvoxamine is effective for the treatment of Japanese patients with GSAD.

Adolescent↗

PubMed2006

Target brain sites of the anxiolytic effect of citalopram, a selective serotonin reuptake inhibitor.

The purpose of the present study was to elucidate the brain regions in which citalopram, a selective serotonin reuptake inhibitor (SSRI), exerts its anxiolytic effects in conditioned fear stress (CFS) in rats, an animal model of anxiety. The effect of citalopram on CFS-induced c-Fos expression was investigated using immunohistochemistry. Systemic administration of citalopram attenuated contextual CFS-induced c-Fos expression in the secondary motor cortex, primary somatosensory cortex, and basolateral nucleus of the amygdala. Among these regions the basolateral nucleus of the amygdala is a likely candidate region in which citalopram exerts its anxiolytic effect.

Amygdala↗

PubMed2006

Effects of co-administration of a selective serotonin reuptake inhibitor and monoamine oxidase inhibitors on 5-HT-related behavior in rats.

5-hydroxytryptamine (5-HT) syndrome is a dangerous condition of 5-HT excess that can occur in the case of co-administration of a monoamine oxidase (MAO) inhibitor and a serotonin reuptake inhibitor (SSRI). The goal of the present study was to investigate the effects of acute administration of MAO inhibitors and subchronic administration of fluvoxamine on 5-HT-related behaviors (head shaking and 5-HT syndrome) in rats treated with 5-hydroxytryptophan (5-HTP). Administration of the non-selective MAO inhibitor, pargyline, and the selective MAO-A inhibitor, clorgyline, resulted in 5-HT syndrome in 5-HTP-treated rats, and subchronic co-administration of fluvoxamine intensified the syndrome. However, administration of the selective MAO-B inhibitor, selegiline, did not induce 5-HT syndrome with or without subchronic fluvoxamine co-administration. These data suggest that non-selective MAO and selective MAO-A inhibitors can induce 5-HT syndrome in humans when co-administered with SSRI. Further, the risk of 5-HT syndrome may be lower with the selective MAO-B inhibitor, selegiline.

Analysis of Variance↗

PubMed2006

Effect of co-administration of subchronic lithium pretreatment and acute MAO inhibitors on extracellular monoamine levels and the expression of contextual conditioned fear in rats.

We investigated the effects of clorgyline [a selective MAO (monoamine oxidase inhibitor)-A inhibitor] and lazabemide (a selective MAO-B inhibitor) on extracellular serotonin, dopamine and noradrenaline concentrations in the medial prefrontal cortex after 1-week treatment with subchronic 0.2% or 0.05% Li2CO3 (p.o.) and the effects on expression of contextual conditioned fear, previously reported to be reduced by facilitation of serotonin neurotransmission. As compared to normal diet controls, the subchronic 0.2% Li2CO3 group showed significantly higher levels of extracellular serotonin, but not noradrenaline. No changes were observed in the 0.05% Li2CO3 group. Acute clorgyline (10 mg/kg) treatments combined with subchronic 0.2% Li2CO3 treatments showed significant increases in extracellular serotonin concentrations, but not in dopamine or noradrenaline, as compared with clorgyline treatment alone. There was an additive effect with combined treatment of subchronic 0.2% Li2CO3 and acute clorgyline on the reduction of conditioned freezing, an index of conditioned fear, and this was not observed with subchronic 0.05% Li2CO3. These behavioral data indicate the functional significance of increased extracellular serotonin concentrations due to combined use of a MAO-A inhibitor with subchronic lithium. Effects of lazabemide (10 mg/kg) on extracellular monoamine concentrations and conditioned fear were slight or negligible, and were not affected by subchronic lithium treatment. The present study suggests that lithium augmentation of the antidepressant effect of MAO inhibitors is mediated by additional increases in the extracellular serotonin concentrations induced by MAO-A inhibition and suggests that the anxiolytic action of MAO inhibitors may be enhanced by lithium.

Animals↗

PubMed2006

5-HT1A receptor agonist affects fear conditioning through stimulations of the postsynaptic 5-HT1A receptors in the hippocampus and amygdala.

Evidence from preclinical and clinical studies has shown that 5-HT(1A) receptor agonists have anxiolytic actions. The anxiolytic actions of 5-HT(1A) receptor agonists have been tested by our previous studies using fear conditioning. However, little is known about the brain regions of anxiolytic actions of 5-HT(1A) receptor agonists in this paradigm. In the present study, we investigated the effects of bilateral microinjections of flesinoxan, a selective 5-HT(1A) receptor agonist, into the hippocampus, amygdala and medial prefrontal cortex on the expression of contextual conditioned freezing and the defecation induced by conditioned fear stress in rats. These results reveal that both intrahippocampal and intraamygdala injections of flesinoxan decreased the expression of conditioned freezing, while injections into the medial prefrontal cortex did not. In addition, intraamygdala injection of flesinoxan attenuated the increased defecation induced by conditioned fear, but injections into the hippocampus and medial prefrontal cortex failed. These results suggest that flesinoxan exerts its anxiolytic actions in the fear conditioning through stimulations of the postsynaptic 5-HT(1A) receptors in the hippocampus and amygdala.

Amygdala↗

PubMed2006

Effects of itraconazole and tandospirone on the pharmacokinetics of perospirone.

Perospirone is an atypical antipsychotic agent originated and clinically used in Japan. Based on an in vitro study, it is reported that perospirone is mainly metabolized to ID-15036 by cytochrome P450 (CYP) 3A4. In this study, the authors investigated the effects of itraconazole, which is a specific inhibitor of CYP3A4, or tandospirone, which is mainly metabolized by CYP3A4 and is expected to competitively inhibit the activity of this enzyme, on single oral dose pharmacokinetics of perospirone. After pretreatment with 200 mg daily of itraconazole or 10 mg daily of tandospirone for 5 days, 9 healthy male subjects received 8 mg of perospirone. Plasma concentrations of perospirone and ID-15036 up to 10 hours after perospirone dosing were measured by high-performance liquid chromatography (HPLC). The metabolism of perospirone was significantly inhibited by treatment with itraconazole but not by tandospirone. The present study suggests that CYP3A4 is significantly involved in metabolism of perospirone in humans.

Adult↗

PubMed2006

Lithium response and Val66Met polymorphism of the brain-derived neurotrophic factor gene in Japanese patients with bipolar disorder.

Lithium is a first-line agent for the treatment of bipolar disorder. A significant association between the Val66Met polymorphism of the brain-derived neurotrophic factor gene and bipolar disorder has been reported. We investigated whether this polymorphism is associated with the response to lithium treatment in Japanese patients with bipolar disorder. Patients had been treated with lithium carbonate for more than 1 year, and the response was retrospectively evaluated. No significant differences were found in the genotype distribution or allele frequency between responders and non-responders. Our results suggested that the brain-derived neurotrophic factor Val66Met polymorphism might not greatly contribute to the efficacy of lithium in bipolar disorder.

Adult↗

PubMed2006

Neuromagnetic source localization of epileptiform activity in patients with graphogenic epilepsy.

PURPOSE: To clarify the source localization of epileptiform activity by using magnetoencephalography (MEG) in patients with graphogenic epilepsy. METHODS: MEG and simultaneous EEG were recorded with a 204-channel whole-head MEG system in two patients with graphogenic epilepsy. During the MEG recordings, the patients performed a set of tasks comprising mental arithmetic calculation, speaking, moving the right arm in a manner resembling writing, writing, and thinking of writing. Equivalent current dipoles (ECD) were calculated for epileptiform discharges on MEG by using a single-dipole model. The ECD were superimposed on the magnetic resonance images of the patients. RESULTS: The task of writing provoked seizures, in which both patients jerked the right arms. Thinking of writing also induced these seizures. In both patients, EEG associated with the seizures showed bursts of spike-and-slow-wave complexes predominantly in the centroparietal region. MEG also showed epileptiform discharges corresponding to the EEG bursts. ECDs obtained from the discharges were clustered in the left centroparietal area. CONCLUSIONS: Thinking of writing was a trigger for the seizures, as well as the task of writing. The source of the epileptiform discharge associated with the seizures was localized in the unilateral centroparietal area. The findings suggest that the centroparietal region plays an important role in the pathophysiology underlying these two graphogenic epilepsy cases.

Adult↗

PubMed2006

Assessment of depressive symptoms in Japanese school children and adolescents using the Birleson Depression Self-Rating Scale.

OBJECTIVE: The aim of this study was to investigate the prevalence of depressive symptoms in children and adolescents in the general Japanese population using a depression self-rating scale and determine whether this prevalence varies according to age, gender, or region. METHOD: The Birleson Depression Self-Rating Scale for children (DSRS) was used to examine the extent to which depressive tendencies were present among 2,453 elementary and middle-school children (6 to 15 years old) in two cities in Japan. RESULTS: The mean DSRS score was high at 8.75 +/- 5.66. A significant increase in score was observed with increasing age. There were no significant differences between regions. Using a DSRS cutoff score of 15 points as a risk of depression, the scores of 14.9% of the subjects exceeded the cutoff. CONCLUSIONS: As determined using the DSRS, a high proportion of Japanese children and adolescents have depressive tendencies.

Adolescent↗

PubMed2005

Genomewide high-density SNP linkage analysis of 236 Japanese families supports the existence of schizophrenia susceptibility loci on chromosomes 1p, 14q, and 20p.

The Japanese Schizophrenia Sib-Pair Linkage Group (JSSLG) is a multisite collaborative study group that was organized to create a national resource for affected sib pair (ASP) studies of schizophrenia in Japan. We used a high-density single-nucleotide-polymorphism (SNP) genotyping assay, the Illumina BeadArray linkage mapping panel (version 4) comprising 5,861 SNPs, to perform a genomewide linkage analysis of JSSLG samples comprising 236 Japanese families with 268 nonindependent ASPs with schizophrenia. All subjects were Japanese. Among these families, 122 families comprised the same subjects analyzed with short tandem repeat markers. All the probands and their siblings, with the exception of seven siblings with schizoaffective disorder, had schizophrenia. After excluding SNPs with high linkage disequilibrium, we found significant evidence of linkage of schizophrenia to chromosome 1p21.2-1p13.2 (LOD=3.39) and suggestive evidence of linkage to 14q11.2 (LOD=2.87), 14q11.2-q13.2 (LOD=2.33), and 20p12.1-p11.2 (LOD=2.33). Although linkage to these regions has received little attention, these regions are included in or partially overlap the 10 regions reported by Lewis et al. that passed the two aggregate criteria of a meta-analysis. Results of the present study--which, to our knowledge, is the first genomewide analysis of schizophrenia in ASPs of a single Asian ethnicity that is comparable to the analyses done of ASPs of European descent--indicate the existence of schizophrenia susceptibility loci that are common to different ethnic groups but that likely have different ethnicity-specific effects.

Chromosomes, Human, Pair 1↗

PubMed2005

Subchronic milnacipran treatment increases basal extracellular noradrenaline concentrations in the medial prefrontal cortex of rats.

In this study, we investigated the acute effects of milnacipran, a serotonin-noradrenaline reuptake inhibitor, following subchronic treatment with milnacipran (30 mg/kg periorally for 7 days) on extracellular noradrenaline, dopamine and serotonin concentrations in the medial prefrontal cortex. Subchronic administration of milnacipran produced significantly higher basal levels of extracellular noradrenaline. Acute milnacipran administration following subchronic milnacipran treatment for 7 days produced a greater increase in extracellular noradrenaline than a single dose of milnacipran alone. The present results suggest that subchronic milnacipran treatment enhances noradrenergic neural transmission beyond that achieved with acute administration of milnacipran alone, but has no effect on serotonergic or dopaminergic neural transmission.

Administration, Oral↗

PubMed2005

Effect of a dopamine D1/5 receptor antagonist on haloperidol-induced inhibition of the acquisition of conditioned fear.

This study examined the effects of combined treatment with the typical antipsychotic drug haloperidol and dopamine D1/5 receptor antagonist SCH 23390 on the acquisition of contextual conditioned fear (re-exposure to an environment paired previously with inescapable electric footshocks), compared with those of various antipsychotic adjuvants, which may increase the effects of antipsychotic drugs. Rats were treated subcutaneously with haloperidol (3 mg/kg) combined with SCH 23390 (0.03 mg/kg) and were given fear conditioning by 5 min footshocks in shock chambers 30 min after the injection. One week after the footshocks, the rats were tested in the same shock chamber without shocks and freezing behavior was observed as an index of fear and anxiety. Haloperidol significantly inhibited the acquisition of conditioned freezing. SCH 23390 combined with haloperidol inhibited the acquisition of conditioned freezing more than either drug alone did. These results suggest that combined dopamine D2-like receptor antagonism and dopamine D1-like receptor antagonism is a promising and effective strategy to increase antipsychotic effects.

Analysis of Variance↗