Haruo Shibuya

Neurotransmitters, receptors and neuropeptides in post-mortem brains of chronic schizophrenic patients

In the analysis of post‐mortem brains of 14 chronic schizophrenic patients and 10 controls, biochemical evidence of a hyperdopaminergic state was found in the basal ganglia of schizophrenics; tyrosine hydroxylase activity was increased with a concomitant increase of homovanillic acid. Unusually high tyrosine hydroxylase activity was noted in 2 schizophrenic cases. The Bmax value of 3H‐spiperone binding for schizophrenics was higher than the controls. We also found increased specific binding of 3H‐kainic acid to the prefrontal cortex in schizophrenics. A negative correlation existed between 3H‐kainic acid binding in the medial frontal cortex, and glutamic acid content in various brain areas. Increased immunoreactivity of substance P was found in more than ten brain areas. Methionineenkephalin was also increased in three areas of the prefrontal cortex of schizophrenics. These results suggest that the hyperdopaminergic state co‐existed with glutamatergic hypofunction and increased neuropeptides in various brain areas of chronic schizophrenic patients.

Identification of a polymorphism in the promoter region of DRD4 associated with the human novelty seeking personality trait.

Polymorphism in the human dopamine D4 receptor gene (DRD4) exon III has been associated in some but not all studies of the human personality trait of Novelty Seeking. We searched for polymorphisms in the 5′ region of DRD4 and identified six polymorphisms as follows: −1217G Ins/Del, −809G/A, −616C/G, −603T Ins/Del, −602(G)8–9, and −521C/T. Associations between these polymorphisms and personality traits measured by the Temperament and Character Inventory (TCI) were investigated in 86 healthy Japanese volunteers. The −521C/T polymorphism was significantly associated with Novelty Seeking (P = 0.0001). Subjects with the C/C genotype exhibited the highest Novelty Seeking scores and those with the T/T genotype exhibited the lowest. A transient expression method revealed that the T variant of the C-521T polymorphism reduces transcriptional efficiency. The present study suggests a contribution of dopamine D4 receptor availability to individual differences in Novelty Seeking behavior.

Serotonin transporter binding in patients with mood disorders: a PET study with [11C](+)McN5652

BACKGROUND Several lines of studies have suggested the involvement of serotonin transporter (5-HTT) in the pathophysiology of mood disorders. The aim of this study was to examine whether 5-HTT binding was altered in patients with mood disorders using positron emission tomography (PET). METHODS Thirteen antidepressant-naive or -free patients with mood disorders and 21 age-matched healthy control subjects participated in this study. The patients consisted of 7 with major depressive disorder (MDD) and 6 with bipolar disorder (BD). Positron emission tomography scans were performed using a selective ligand for 5-HTT, [11C](+)McN5652. The uptake was quantified in the thalamus and midbrain by graphical method with reference tissue, and binding potential (BP) was used for the index of 5-HTT binding. RESULTS Binding potential in the thalamus was significantly increased in patients with mood disorders as compared to control subjects, whereas BP in the midbrain did not differ between the groups. Subgroup comparison showed that MDD patients had significantly higher BP in the thalamus compared to control subjects. Binding potential of the thalamus was higher by approximately 22% in the combined patients and 23% in MDD patients relative to control subjects. CONCLUSIONS These findings may suggest the possibility of altered 5-HTT in patients with mood disorders. Functional abnormality in the thalamus may be involved in the pathophysiology of mood disorders.

A circadian rhythm of tryptophan hydroxylase in rat pineals.

Recent work has established that the circadian rhythms of the pineal N-acetyltransferase, N-acetylserotonin and melatonin clearly exist with high values during darkness and low during light period, while the pineal serotonin rhythm is opposite in phase. Regarding the circadian rhythm of the pineal tryptophan hydroxylase, there have been very few studies and it has been believed that no daily fluctuation exists. The purpose of the present study is to describe the presence of the circadian changes in the enzyme activity by means of a sensitive and reliable assay method developed by Ichiyama et al. 8,9. Adult male Wistar rats (200-300 g) were housed in a light-tight room under diurnal lighting conditions (lights on from 7.00 a.m. to 7.00 p.m.) for about 3 weeks before experiments. The room was illuminated with overhead cool-white fluorescent lamps providing 100-120 lux as measured at the bottom of the cage. Oriental MF rat chow containing 24.6 ~ protein and 0.22 ~ tryptophan and tap water were available ad libitum. Rats were killed by decapitation every 4 h from 10 a.m. During the dark period they were treated under a dim red light. The pineals were rapidly removed in the cold box which was kept at around 0 °C and homogenized in 0.1 ml of ice-cold 0.01 M Tris.acetate buffer, pH 7.4, containing 1 ~ Lubrol-WX using a glass-Teflon homogenizer. Tryptophan hydroxylase activity was assayed according to the method of Ichiyama et al. 8. The preincubation mixture in the Thunberg tube whose air was replaced with nitrogen gas contained 31.3 m M dithiothreitol, 0.05-mM ferrous ammonium sulfate, 225-300 U catalase, 0.1 M Tris.acetate buffer, pH 8.1, to give a final pH 8.1, and pineal homogenate in a total volume of 0.4 ml. The tubes were preincubated at 30 °C for 20 min under anaerobic conditions. The hydroxylation was started by adding an aliquot of the preincubated enzyme. Immediately, the incubation tube was connected with a vial using a tight-fitting rubber tube. The vial contained a filter paper (80 × 16 mm, Whatman No. 1) which had been previously absorbed with

Further association study on dopamine D2 receptor variant S311C in schizophrenia and affective disorders

The dopamine D2 receptor gene is a candidate gene for schizophrenia because the potency of certain neuroleptics correlates with their affinity for this receptor. Case-control studies in 291 schizophrenics, 78 patients with affective disorders, and 579 controls on an association of a molecular variant of S311C of the dopamine D2 receptor with psychiatric disorders were conducted. The frequency of individuals with S311C was significantly higher in schizophrenics with the absence of negative symptoms (17.1%, P < 0.00001), but similar in schizophrenics with the presence of negative symptoms (5.7%, P = 0.46) when compared with the controls (4.1%). The frequency of S311C was significantly higher in familial schizophrenics from one local area but not in those from other areas. It was significant that S311C was frequently present in patients with mood-incongruent psychotic affective disorders (33.3%, P < 0.0001), but not in those with other affective disorders. These data suggest that S311C might be one of the genetic factors for symptomatic dimensions of delusions and hallucinations and might be involved in underlying clinical heterogeneity in schizophrenia and affective disorders.

Identification of a compound short tandem repeat stretch in the 5'-upstream region of the cholecystokinin gene, and its association with panic disorder but not with schizophrenia.

The cholecystokinin gene (CCK) is thought to play a role in the pathogenesis of both panic disorder1–4 and schizophrenia.5 In this study, we have extended the 5′-upstream sequence of the CCK gene, and identified a compound short tandem repeat (STR), located approximately −2.2 to −1.8 kb from the cap site. This STR was found to be polymorphic with ten different allele lengths. Case-control studies using 73 panic patients, 305 schizophrenics and 252 controls showed a significant allelic association with panic disorder (P = 0.025), but not with schizophrenia. Dividing the STR alleles into three classes according to length, Long (L), Medium (M) and Short (S), produced strong genotypic (MM) (nominal P = 0.0014) and allelic (M) (nominal P = 0.0079) associations with panic disorder. screening the newly extended promoter region detected not only the previously identified −36c>t and −188a>g single nucleotide polymorphisms (snps) but a new rare snp, −345g>C. Neither of the former two SNPs showed significant association with either panic disorder or schizophrenia. Haplotypic distributions of the STR and SNPs −188 and −36 were significantly different between panic samples and controls (P = 0.0003). These findings suggest that the novel STR or a nearby variant may confer susceptibility to the development of panic disorder.

Blockade of behavioral sensitization to methamphetamine by lesion of hippocampo-accumbal pathway

The present studies were carried out to explore a role of the hippocampal efferents in the development of the locomotor augmentation induced by repeated methamphetamine administrations. For this purpose, electrolytic lesions of either the dorsal fornix or the fimbria fornix were made bilaterally in rats. The latter treatment, not the former, blocked the behavioral sensitization. These results suggest that the hippocampo-accumbal pathway may play an important role in the development of the sensitization.

Possible association between a haplotype of the GABA-A receptor alpha 1 subunit gene (GABRA1) and mood disorders

BACKGROUND The gamma-aminobutyric acid (GABA) neurotransmitter system has been implicated in the pathogenesis of mood disorders. The GABRA1 gene encodes one of the subunits of GABA-A receptor and is located on human chromosome 5q34-q35, which is a region reportedly linked to mood disorders. We examined the GABRA1 gene as a candidate for mood disorders. METHODS We performed mutation screening of GABRA1 in 24 Japanese bipolar patients and evaluated associations in Japanese case-control subjects consisting of 125 patients with bipolar disorder, 147 patients with depressive disorders, and 191 healthy control subjects. Associations were confirmed in the National Institute of Mental Health (NIMH) Initiative Bipolar Pedigrees, which consists of 88 multiplex pedigrees with 480 informative persons. RESULTS We identified 13 polymorphisms in the GABRA1 gene. Nonsynonymous mutations were not found. Association of a specific haplotype with affective disorders was suggested in the Japanese case-control population (corrected p=.0008). This haplotype association was confirmed in the NIMH pedigrees (p=.007). CONCLUSIONS These results indicate that the GABRA1 gene may play a role in the etiology of bipolar disorders.

Sigma receptors in schizophrenic cerebral cortices.

Antipsychotics represent high affinity for sigma receptors and sigma-like drugs often have the psychotomimetic properties. Besides, the receptors are unevenly distributed in human brain. These findings suggest that sigma receptors might be involved in the pathophysiology of schizophrenia. Sigma receptors in rat and human brain were measured with [3H]-1, 3, di-o-tolylguanidine (DTG) and non-specific binding of [3H]DTG was determined in the presence of 10−5M haloperidol. Monovalent and divalent cations strongly inhibited [3H]DTG binding. Glutamate, aspartate and glycine also decreased the binding to human cerebral membranes. With post-mortem brain samples from 12 schizophrenics and 10 controls, sigma receptors were measured in 17 areas of cerebral cortex. Sigma receptors binding showed the regional differences in the cortex, but no significant differences between schizophrenics and controls were observed except the superior parietal cortex where the binding significantly increased in the schizophrenic group. These results suggest that sigma receptors in cerebral cortices might not be directly concerned with the pathophysiological role in schizophrenia.

Association study on the DUSP6 gene, an affective disorder candidate gene on 12q23, performed by using fluorescence resonance energy transfer-based melting curve analysis on the LightCycler.

We introduced a new genotyping method, fluorescence resonance energy transfer-based melting curve analysis on the LightCycler, for the analysis of the gene, DUSP6 (dual specificity MAP kinase phosphatase 6), in affective disorder patients. The DUSP6 gene is located on chromosome 12q22–23, which overlaps one of the reported bipolar disorder susceptibility loci. because of its role in intracellular signalling pathways, the gene may be involved in the pathogenesis of affective disorders not only on the basis of its position but also of its function. we performed association analysis using a t>G polymorphism that gives rise to a missense mutation (Leu114Val). No evidence for a significant disease-causing effect was found in Japanese unipolars (n = 132) and bipolars (n = 122), when compared with controls (n = 299). More importantly, this study demonstrates that melting curve analysis on the LightCycler is an accurate, rapid and robust method for discriminating genotypes from biallelic markers. This strategy has the potential for use in high throughput scanning for and genotyping of single nucleotide polymorphisms (SNPs).