Characteristics of Visual Cognition in Patients with Anoxic Encephalopathy: An Eye-tracking Study.

Objectives: : Despite the frequent occurrence of visual cognitive impairment after anoxic encephalopathy, only a few studies have analyzed gaze movements following encephalopathy. This study determined the visual cognitive characteristics of patients with anoxic encephalopathy using an eye-tracking system. Methods: : This study included ten patients with anoxic encephalopathy and ten age/sex-matched controls. Factors for anoxic encephalopathy onset and brain imaging findings were extracted from medical records. An eye-tracking system was used to track eye movements during three visual search tasks (pop-out, serial search, and saliency) in patient and healthy control groups. The average target search time, number of saccades, and number of fixations to salient stimuli were compared. Results: : Stagnant blood flow, observed in six of ten patients, was the most common cause of disease onset, four of whom exhibited hypoperfusion in bilateral occipital or parietal lobes on single-photon emission computed tomography. The patient group required longer search times during all visual search tasks and a higher number of saccades during pop-out and serial search tasks. However, no significant difference was observed between the two groups for the number of fixations to salient stimuli during the saliency task. Conclusions: : Following anoxic encephalopathy, bottom-up (pop-out task) and top-down (serial search task) gaze control were considered impaired because of extensive parieto-occipital lobe damage after blood flow stagnation. Patients exhibited reduced top-down function for finding targets (serial search task) but relatively retain inhibitory function for salient stimuli (saliency task). Gaze analysis can be used to reveal the clinical characteristics of anoxic encephalopathy.

A rare genetic variant in the cleavage site of prepro-orexin is associated with idiopathic hypersomnia.

Idiopathic hypersomnia (IH) is a rare, heterogeneous sleep disorder characterized by excessive daytime sleepiness. In contrast to narcolepsy type 1, which is a well-defined type of central disorders of hypersomnolence, the etiology of IH is poorly understood. No susceptibility loci associated with IH have been clearly identified, despite the tendency for familial aggregation of IH. We performed a variation screening of the prepro-orexin/hypocretin and orexin receptors genes and an association study for IH in a Japanese population, with replication (598 patients and 9826 controls). We identified a rare missense variant (g.42184347T>C; p.Lys68Arg; rs537376938) in the cleavage site of prepro-orexin that was associated with IH (minor allele frequency of 1.67% in cases versus 0.32% in controls, P = 2.7 × 10-8, odds ratio = 5.36). Two forms of orexin (orexin-A and -B) are generated from cleavage of one precursor peptide, prepro-orexin. The difference in cleavage efficiency between wild-type (Gly-Lys-Arg; GKR) and mutant (Gly-Arg-Arg; GRR) peptides was examined by assays using proprotein convertase subtilisin/kexin (PCSK) type 1 and PCSK type 2. In both PCSK1 and PCSK2 assays, the cleavage efficiency of the mutant peptide was lower than that of the wild-type peptide. We also confirmed that the prepro-orexin peptides themselves transmitted less signaling through orexin receptors than mature orexin-A and orexin-B peptides. These results indicate that a subgroup of IH is associated with decreased orexin signaling, which is believed to be a hallmark of narcolepsy type 1.

Genome-wide association study of idiopathic hypersomnia in a Japanese population.

Idiopathic hypersomnia (IH) is a rare sleep disorder characterized by excessive daytime sleepiness, great difficulty upon awakening, and prolonged sleep time. In contrast to narcolepsy type 1, which is a well-recognized hypersomnia, the etiology of IH remains poorly understood. No susceptibility loci for IH have been identified, although familial aggregations have been observed among patients with IH. Narcolepsy type 1 is strongly associated with human leukocyte antigen (HLA)-DQB1*06:02; however, no significant associations between IH and HLA alleles have been reported. To identify genetic variants that affect susceptibility to IH, we performed a genome-wide association study (GWAS) and two replication studies involving a total of 414 Japanese patients with IH and 6587 healthy Japanese individuals. A meta-analysis of the three studies found no single-nucleotide polymorphisms (SNPs) that reached the genome-wide significance level. However, we identified several candidate SNPs for IH. For instance, a common genetic variant (rs2250870) within an intron of PDE9A was suggestively associated with IH. rs2250870 was significantly associated with expression levels of PDE9A in not only whole blood but also brain tissues. The leading SNP in the PDE9A region was the same in associations with both IH and PDE9A expression. PDE9A is a potential target in the treatment of several brain diseases, such as depression, schizophrenia, and Alzheimer's disease. It will be necessary to examine whether PDE9A inhibitors that have demonstrated effects on neurophysiologic and cognitive function can contribute to the development of new treatments for IH, as higher expression levels of PDE9A were observed with regard to the risk allele of rs2250870. The present study constitutes the first GWAS of genetic variants associated with IH. A larger replication study will be required to confirm these associations. Supplementary Information: The online version contains supplementary material available at 10.1007/s41105-021-00349-2.

Paradoxical changes in mood-related behaviors on continuous social isolation after weaning.

Continuous social isolation (SI) from an early developmental stage may have different effects in youth and adulthood. Moreover, SI is reported to impair neuronal plasticity. In this study, we used post-weaning rats to compare the impact of continuous SI on depressive-like, anxiety-related, and fear-related behaviors and neuronal plasticity in puberty and adulthood. Furthermore, we assessed the effect of lithium on behavioral changes and neuronal plasticity. Continuous SI after weaning induced depressive-like behaviors in puberty; however, in adulthood, depressive-like and anxiety-related behaviors did not increase, but-paradoxically-decreased in comparison with the controls. The decreased expression of neuronal plasticity-related proteins in the hippocampus in puberty was more prominent in the prefrontal cortex and hippocampus in adulthood. In contrast, SI after weaning tended to decrease fear-related behaviors in puberty, a decrease which was more prominent in adulthood with increased neuronal plasticity-related protein expression in the amygdala. Lithium administration over the last 14 days of the SI-induced period removed the behavioral and expression changes of neuronal plasticity-related proteins observed in puberty and adulthood. Our findings suggest that the extension of the duration of SI from an early developmental stage does not simply worsen depressive-like behaviors; rather, it induces a behavior linked to neuronal plasticity damage. Lithium may improve behavioral changes in puberty and adulthood by reversing damage to neuronal plasticity. The mechanisms underlying the depressive-like and anxiety-related behaviors may differ from those underlying fear-related behaviors.

A variant at 9q34.11 is associated with HLA-DQB1*06:02 negative essential hypersomnia.

Essential hypersomnia (EHS) is a lifelong disorder characterized by excessive daytime sleepiness without cataplexy. EHS is associated with human leukocyte antigen (HLA)-DQB1*06:02, similar to narcolepsy with cataplexy (narcolepsy). Previous studies suggest that DQB1*06:02-positive and -negative EHS are different in terms of their clinical features and follow different pathological pathways. DQB1*06:02-positive EHS and narcolepsy share the same susceptibility genes. In the present study, we report a genome-wide association study with replication for DQB1*06:02-negative EHS (408 patients and 2247 healthy controls, all Japanese). One single-nucleotide polymorphism, rs10988217, which is located 15-kb upstream of carnitine O-acetyltransferase (CRAT), was significantly associated with DQB1*06:02-negative EHS (P = 7.5 × 10-9, odds ratio = 2.63). The risk allele of the disease-associated SNP was correlated with higher expression levels of CRAT in various tissues and cell types, including brain tissue. In addition, the risk allele was associated with levels of succinylcarnitine (P = 1.4 × 10-18) in human blood. The leading SNP in this region was the same in associations with both DQB1*06:02-negative EHS and succinylcarnitine levels. The results suggest that DQB1*06:02-negative EHS may be associated with an underlying dysfunction in energy metabolic pathways.

The co-occurrence of zinc deficiency and social isolation has the opposite effects on mood compared with either condition alone due to changes in the central norepinephrine system.

Nutritional and social environmental problems during the early stages of life are closely associated with the pathophysiology of mood disorders such as depression. Disruption or dysfunction of the central norepinephrine (NE) system is also considered to play a role in mood disorders. Therefore, we evaluated the effects of zinc deficiency and/or social isolation on mood and changes in the central NE system using rats. Compared with the controls, the rats subjected to zinc deficiency or social isolation alone exhibited increased anxiety-related behavior in the elevated plus maze and greater depression-like behavior in the forced swim test. However, the co-occurrence of zinc deficiency and social isolation resulted in decreased anxiety-related behavior and control levels of depression-like behavior. Social isolation alone decreased the rats' cerebral NE concentrations. The expression of the NE transporter was not affected by social isolation alone, but its expression in the locus coeruleus was markedly decreased by the co-occurrence of social isolation and zinc deficiency, and this change was accompanied by an increase in the blood concentration of 3-methoxy-4-hydroxyphenylglycol, which is a marker of central NE system activity. These findings suggest that zinc deficiency or social isolation alone induce anxious or depressive symptoms, but the presence of both conditions has anxiolytic or antidepressive effects. Furthermore, these opposing effects of mood-related behaviors were found to be associated with changes in the central NE system.

An association analysis of HLA-DQB1 with narcolepsy without cataplexy and idiopathic hypersomnia with/without long sleep time in a Japanese population.

Narcolepsy without cataplexy (NA w/o CA) (narcolepsy type 2) is a lifelong disorder characterized by excessive daytime sleepiness and rapid eye movement (REM) sleep abnormalities, but no cataplexy. In the present study, we examined the human leukocyte antigen HLA-DQB1 in 160 Japanese patients with NA w/o CA and 1,418 control subjects. Frequencies of DQB1*06:02 were significantly higher in patients with NA w/o CA compared with controls (allele frequency: 16.6 vs. 7.8%, P=1.1×10(-7), odds ratio (OR)=2.36; carrier frequency: 31.3 vs. 14.7%, P=7.6×10(-8), OR=2.64). Distributions of HLA-DQB1 alleles other than DQB1*06:02 were compared between NA w/o CA and narcolepsy with cataplexy (NA-CA) to assess whether the genetic backgrounds of the two diseases have similarities. The distribution of the HLA-DQB1 alleles in DQB1*06:02-negative NA w/o CA was significantly different from that in NA-CA (P=5.8×10(-7)). On the other hand, the patterns of the HLA-DQB1 alleles were similar between DQB1*06:02-positive NA w/o CA and NA-CA. HLA-DQB1 analysis was also performed in 186 Japanese patients with idiopathic hypersomnia (IHS) with/without long sleep time, but no significant associations were observed.

New susceptibility variants to narcolepsy identified in HLA class II region.

Narcolepsy, a sleep disorder characterized by excessive daytime sleepiness, cataplexy and rapid eye movement sleep abnormalities, is tightly associated with human leukocyte antigen HLA-DQB1*06:02. DQB1*06:02 is common in the general population (10-30%); therefore, additional genetic factors are needed for the development of narcolepsy. In the present study, HLA-DQB1 in 664 Japanese narcoleptic subjects and 3131 Japanese control subjects was examined to determine whether HLA-DQB1 alleles located in trans of DQB1*06:02 are associated with narcolepsy. The strongest association was with DQB1*06:01 (P = 1.4 × 10(-10), odds ratio, OR = 0.39), as reported in previous studies. Additional predisposing effects of DQB1*03:02 were also found (P = 2.5 × 10(-9), OR = 1.97). A comparison between DQB1*06:02 heterozygous cases and controls revealed dominant protective effects of DQB1*06:01 and DQB1*05:01. In addition, a single-nucleotide polymorphism-based conditional analysis controlling for the effect of HLA-DQB1 was performed to determine whether there were other independent HLA associations outside of HLA-DQB1. This analysis revealed associations at HLA-DPB1 in the HLA class II region (rs3117242, P = 4.1 × 10(-5), OR = 2.45; DPB1*05:01, P = 8.1 × 10(-3), OR = 1.39). These results indicate that complex HLA class II associations contribute to the genetic predisposition to narcolepsy.

Mania: not the opposite of depression, but an extension? Neuronal plasticity and polarity.

What underlies bipolar disorder? What pathophysiologic process can produce symptoms that are apparently polar opposites? Recent studies of neuronal plasticity suggest a mechanism. Both zinc deficiency and social isolation impair neuronal plasticity; both are associated with major depression. Yet when zinc deficiency and social isolation occur together, they are associated with aggression, not with depression. On that basis, and according to additional findings in rats reported herein, it was inferred that moderate impairment of neuronal plasticity induces a depressive state, but that further impairment of neuronal plasticity induces not more depression, but a manic state. However, not only neuronal plasticity, but also some kind of load toward neuronal function can influence polarity or symptoms of mood disorder. Our hypothesis is that mania is an extension of depression from the perspective of neuronal plasticity, and that multiaxial evaluation by neuronal plasticity and neuronal load is useful to elucidate the pathophysiology of mood disorder. Using this hypothesis, many clinical aspects that have been heretofore difficult to interpret can be understood. A mood stabilizer or electric convulsive therapy is often used for the treatment of mood disorder, but it has remained unclear why such therapies are useful for both mania and depression. This hypothesis can explain how mood stabilizers or electric convulsive therapy can improve both mania and depression through the recovery of neuronal plasticity. It is difficult to explain the pathophysiology of manic switching by antidepressants solely from the perspective of the impairment of neuronal plasticity. To interpret this phenomenon, the action of antidepressants to neuronal load should be regarded as the other axis from neuronal plasticity. Based on this hypothesis, it is expected that the pathophysiology of mood disorder and clinical mechanism of mood stabilizers and antidepressants can be understood in an integrated manner.

Region-specific causal mechanism in the effects of ammonia on cerebral glucose metabolism in the rat brain.

Ammonia, which is considered to be the main agent responsible for hepatic encephalopathy, inhibits oxidative glucose metabolism in the brain. However, the effects of ammonia on cerebral glucose metabolism in different brain regions remains unclear. To clarify this issue, we added ammonia directly to fresh rat brain slices and measured its effects on glucose metabolism. Dynamic positron autoradiography with [(18)F]2-fluoro-2-deoxy-D-glucose and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium (WST-1) colorimetric assay revealed that ammonia significantly increased the cerebral glucose metabolic rate and depressed mitochondrial function, as compared to the unloaded control in each of the brain regions examined (cerebral cortex, striatum, and cerebellum), reflecting increased glycolysis that compensates for the decrease in aerobic metabolism. Pre-treatment with (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), a N-methyl-D-aspartate (NMDA) receptor antagonist, significantly attenuated these changes induced by ammonia in cerebellum, but not in cerebral cortex or striatum. The addition of ammonia induced an increase in cyclic guanosine monophosphate (cGMP) levels in cerebellum, but not in cerebral cortex or striatum, reflecting the activation of the NMDA receptor-nitric oxide-cGMP pathway. These results suggested that NMDA receptor activation is responsible for the impairment of glucose metabolism induced by ammonia specifically in cerebellum.

[Multiaxial evaluation of the pathophysiology of mood disorder and therapeutic mechanisms of clinical drugs by neuronal plasticity and neuronal load].

Impairment of neuronal plasticity is important in the pathophysiology of mood disorder. Both zinc deficiency and social isolation impair neuronal plasticity. Both cause a depressive state. However, in experiments using animals, their combined loading induced manic-like behavior. Therefore, it was inferred that moderate impairment of neuronal plasticity induces a depressive state, and that further impairment of neuronal plasticity induces a manic state. However, some kind of load toward neuronal function through neural transmission can influence mood disorder symptoms without direct effects on neuronal plasticity. Our hypothesis is that mania is an aggravation of depression from the perspective of neuronal plasticity, and that multiaxial evaluation by neuronal plasticity and neuronal load through neural transmission is useful for understanding the pathophysiology of mood disorder. There are many clinical aspects that have been difficult to interpret in mood disorder: Why is a mood stabilizer or electric convulsive therapy useful for both mania and depression? What is the pathophysiology of the mixed state? Why does manic switching by an antidepressant occur or not? Our hypothesis is useful to understand these aspects, and using this hypothesis, it is expected that the pathophysiology of mood disorder and clinical mechanism of mood stabilizers and antidepressants can now be understood as an integrated story.

Effect of dietary zinc deficiency on ischemic vulnerability of the brain.

Deficiency of zinc, which modulates glutamate release, might increase ischemic vulnerability of the brain. We examined effects of dietary zinc deficiency for 2 weeks on ischemic vulnerability in several brain regions using dynamic positron autoradiography technique and [18F]2-fluoro-2-deoxy-d-glucose with rat brain slices. In the normal diet group, the cerebral glucose metabolic rate (CMRglc) was not significantly different from that of the ischemia-unloaded control even after the loading of ischemia for 45 min. However, in the zinc-deficient diet group, CMRglc was significantly lower than that of the ischemia-unloaded control after loading of ischemia for 45 min. With treatment of MK-801 (NMDA receptor antagonist) from the start of ischemia loading, CMRglc was not significantly different from that of the ischemia-unloaded control. These findings, obtained for all analyzed brain regions, suggest that dietary zinc deficiency increased ischemic vulnerability in the brain, and that glutamate might contribute to this effect through activation of the NMDA receptor.

Effects of antidepressants and mood stabilizers on serum levels of adiponectin.

The effect of antidepressants and mood stabilizers on serum levels of adiponectin was investigated. Fluvoxamine (30 and 50 mg/kg/day) or lithium (40 and 60 mg/kg/day) was dissolved in distilled water and administered orally to rats every day for 4 weeks. Fluvoxamine (50 mg/kg/day) alone significantly elevated the serum level of adiponectin, but no significant difference was found between other drug-treated groups and the control group. This difference of these drugs' effectiveness on serum adiponectin might contribute to their differences of action mechanisms and therapeutic effects.

Lentivirally mediated GSK-3ß silencing in the hippocampal dentate gyrus induces antidepressant-like effects in stressed mice.

Inhibition of glycogen synthase kinase-3 (GSK-3) by pharmacological tools can produce antidepressant-like effects in rodents. However, the GSK-3 isoform(s) and brain region(s) involved in regulating these behavioural effects remain elusive. We studied the effects of bilateral intra-hippocampal injections of lentivirus-expressing short-hairpin (sh)RNA targeting GSK-3ß on behavioural performance in mice subjected to chronic stress. Pre-injection of lentivirus-expressing GSK-3ß shRNA into the hippocampal dentate gyrus significantly decreased immobility time in both forced swim and tail suspension tests, while the locomotor activity of these mice was unchanged. These results suggest that lentiviral GSK-3ß shRNA injection induces antidepressant-like effects in chronically stressed mice. Under these conditions, the expression levels of GSK-3ß were persistently and markedly reduced in the hippocampus following GSK-3ß shRNA injection. To our knowledge, this is the first demonstration that a single injection of lentivirus-expressing GSK-3ß shRNA in the hippocampal dentate gyrus of chronically stressed mice has antidepressant-like effects elicited by gene silencing.

Effects of vitamin E supplementation on plasma membrane permeabilization and fluidization induced by chlorpromazine in the rat brain.

Neurotransmitter receptors play a key role in most research on antipsychotic drugs, but little is known about the effects of these drugs on the plasma membrane in the central nervous system. Therefore, we investigated whether chlorpromazine (CPZ), a typical phenothiazine antipsychotic drug, affects the plasma membrane integrity in the rat brain, and if so, whether these membrane alterations can be prevented by dietary supplementation with vitamin E, which has been shown to be an antioxidant and also a membrane-stabilizer. Leakage of [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG)-6-phosphate from rat striatal slices and decrease in 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy were used as indexes for plasma membrane permeabilization and fluidization, respectively. CPZ induced leakage of [(18)F]FDG-6-phosphate from striatal slices, and the leakage was delayed in the vitamin E-supplemented group compared to that in the normal diet group. The decrease in plasma membrane anisotropy induced by CPZ was significantly attenuated by vitamin E supplementation. Chronic treatment with alpha-phenyl-N-tert-butyl nitrone, a free radical scavenger, had no effect on CPZ-induced plasma membrane permeabilization, and the treatment with CPZ did not induce lipid peroxidation. CPZ can reduce plasma membrane integrity in the brain, and this reduction can be prevented by vitamin E via its membrane-stabilizing properties, not via its antioxidant activity.

Effects of haloperidol and its pyridinium metabolite on plasma membrane permeability and fluidity in the rat brain.

The use of antipsychotic drugs is limited by their tendency to produce extrapyramidal movement disorders such as tardive dyskinesia and parkinsonism. In previous reports it was speculated that extrapyramidal side effects associated with the butyrophenone neuroleptic agent haloperidol (HP) could be caused in part by the neurotoxic effect of its pyridinium metabolite (HPP(+)). Although both HPP(+) and HP have been shown to induce neurotoxic effects such as loss of cell membrane integrity, no information exists about the difference in the neurotoxic potency, especially in the potency to induce plasma membrane damage, between these two agents. In the present study, we compared the potency of the interaction of HPP(+) and HP with the plasma membrane integrity in the rat brain. Membrane permeabilization (assessed as [(18)F]2-fluoro-2-deoxy-d-glucose-6-phosphate release from brain slices) and fluidization (assessed as the reduction in the plasma membrane anisotropy of 1,6-diphenyl 1,3,5-hexatriene) were induced by HPP(+) loading (at >or=100 microM and >or=10 microM, respectively), while comparable changes were induced only at a higher concentration of HP (=1 mM). These results suggest that HPP(+) has a higher potency to induce plasma membrane damage than HP, and these actions of HPP(+) may partly underlie the pathogenesis of HP-induced extrapyramidal side effects.

Biphasic mechanism of the toxicity induced by 1-methyl-4-phenylpyridinium ion (MPP+) as revealed by dynamic changes in glucose metabolism in rat brain slices.

1-Methyl-4-phenylpyridinium (MPP+) is a well-known neurotoxin which causes a clinical syndrome similar to Parkinson's disease. The classical mechanism of MPP+ toxicity involves its entry into cells through the dopamine transporter (DAT) to inhibit aerobic glucose metabolism, while recent studies suggest that an oxidative mechanism may contribute to the toxicity of MPP+. However, it has not been adequately determined what role these two mechanisms play in the development of neurotoxicity after MPP+ loading in the brain. To clarify this issue, MPP+ was added directly to fresh rat brain slices and the dynamic changes in the cerebral glucose metabolic rate (CMRglc) produced by MPP+ were serially and two-dimensionally measured using the dynamic positron autoradiography technique with [(18)F]2-fluoro-2-deoxy-D-glucose as a tracer. MPP+ dose-dependently increased CMRglc in each of the brain regions examined, reflecting enhanced glycolysis compensating for the decrease in aerobic metabolism. Treatment with DAT inhibitor GBR 12909 significantly attenuated the enhanced glycolysis induced by 10 microM MPP+ in the striatum. Treatment with free radical spin trap alpha-phenyl-N-tert-butylnitrone (PBN) significantly attenuated the enhancement of glycolysis induced by 100 microM MPP+ in all brain regions. These results suggest that the mechanism of the toxicity of MPP+ is biphasic and consists of a DAT-mediated mechanism selective for dopaminergic regions at a lower concentration of MPP+ (10 microM), and an oxidative mechanism that occurs at a higher concentration of MPP+ (100 microM) and is not restricted to dopaminergic regions.