Temporal Fluctuations of Suicide Mortality in Japan from 2009 to 2023 Using Government Databases

In Japan, suicide mortalities consistently decreased before the COVID-19 pandemic (from 2009 to 2019) but, conversely, increased after the pandemic outbreak from 2020 to 2022. To provide up-to-date suicide statistics in Japan, this study determined the temporal fluctuations of standardized suicide mortalities (SMRs), disaggregated by sex and age, by joinpoint regression analysis using the government suicide database, named the "Basic Data on Suicide in Region". From January 2009 to December 2023, three temporal fluctuation patterns of SMRs pertaining to working age and older adults were detected, such as attenuations of decreasing trends before the COVID-19 pandemic (from around the mid-2010s), a sharply increasing trend that coincided with the pandemic outbreak, and gradually decreased during the pandemic, but no changes at the end of the COVID-19 pandemic. In particular, the SMRs of working-age females sharply increased concurrently with the pandemic outbreak, whereas those of males did not change. However, before the pandemic, decreasing trends of the SMRs of working-age males diminished in the mid-2010s, but those of females consistently decreased. The SMRs of working-age males indicated non-significant but sharply increasing trends in early 2022, a trend that was not observed for females. In contrast to working-age adults, the SMRs of adolescents already began to increase in the mid-2010s and also indicated consistently increasing trends between the periods during and after the pandemic. These results suggest, contrary to our expectations, that the impacts of both the outbreak and end of the COVID-19 pandemic were limited regarding the increase in SMRs from 2020. Therefore, when revising suicide prevention programs in the post-COVID-19 era, it should be noted that focusing on pandemic-associated factors alone is not sufficient.

Impacts of Working Hours, Wages, and Regular Employment Opportunity on Suicide Mortalities of Employed and Unemployed Individuals before and during the COVID-19 Pandemic in Japan

Standardized suicide mortality rates per 100,000 population (SMRs) in Japan consistently decreased from 2009-2019, but these decreasing trends were reversed to increase in 2020. To clarify the mechanisms of recent increasing suicide in Japan, temporal fluctuations of SMRs disaggregated by sex and employment status (employed and unemployed individuals) and labor indices such as working hours, wages, and regular employment opportunity index (REO) from January 2012 to June 2023 were analyzed using interrupted time-series analysis. Additionally, temporal causalities from labor indices to SMRs were analyzed using vector autoregressive and non-linear auto-regressive distributed lag analyses. Decreasing trends among employed SMRs of both sexes were attenuated after the enactment of the "Work Style Reform Program" in 2018, but male SMRs were unaffected by the COVID-19 pandemic. However, female employed SMRs sharply increased, synchronized with the "Work Style Reform Act" and the COVID-19 pandemic outbreak (the COVID-19 impact was greater than the "Work Style Reform Act"). Additionally, unemployed SMRs of both sexes sharply increased with the revision and scale-down of countermeasures against economic deterioration caused by COVID-19 ("revision of economic supportive countermeasures against economic deterioration caused by COVID-19"). Unexpectedly, after enacting the "Work Style Reform Act", wages decreased due to possibly decreasing working hours. Increasing REO, which consistently increased, was a protective factor for male suicides, but unemployed SMRs were not affected by any labor indices. It has been established that controlling a heavy workload plays an important role in suppressing the deterioration of physical and mental conditions, including suicide; however, this study suggested that, at least within appropriate ranges of working hours, decreasing working hours due to excessive management probably contributes to increasing suicides of some vulnerable individuals via de-creasing their wages. Although governmental welfare and economic support measures had to be revised according to rapidly changing situations during the COVID-19 pandemic, this study also suggested that temporal gaps among a part of revisions of several welfare and economic support measures were unexpectedly involved in drastically/sharply increasing suicides of unemployed individuals in 2022.

Age and sex effects on paired-pulse suppression and prepulse inhibition of auditory evoked potentials

Responses to a sensory stimulus are inhibited by a preceding stimulus; if the two stimuli are identical, paired-pulse suppression (PPS) occurs; if the preceding stimulus is too weak to reliably elicit the target response, prepulse inhibition (PPI) occurs. PPS and PPI represent excitability changes in neural circuits induced by the first stimulus, but involve different mechanisms and are impaired in different diseases, e.g., impaired PPS in schizophrenia and Alzheimer's disease and impaired PPI in schizophrenia and movement disorders. Therefore, these measures provide information on several inhibitory mechanisms that may have roles in clinical conditions. In the present study, PPS and PPI of the auditory change-related cortical response were examined to establish normative data on healthy subjects (35 females and 32 males, aged 19-70 years). We also investigated the effects of age and sex on PPS and PPI to clarify whether these variables need to be considered as biases. The test response was elicited by an abrupt increase in sound pressure in a continuous sound and was recorded by electroencephalography. In the PPS experiment, the two change stimuli to elicit the cortical response were a 15-dB increase from the background of 65 dB separated by 600 ms. In the PPI experiment, the prepulse and test stimuli were 2- and 10-dB increases, respectively, with an interval of 50 ms. The results obtained showed that sex exerted similar effects on the two measures, with females having stronger test responses and weaker inhibition. On the other hand, age exerted different effects: aging correlated with stronger test responses and weaker inhibition in the PPS experiment, but had no effects in the PPI experiment. The present results suggest age and sex biases in addition to normative data on PPS and PPI of auditory change-related potentials. PPS and PPI, as well as other similar paradigms, such as P50 gating, may have different and common mechanisms. Collectively, they may provide insights into the pathophysiologies of diseases with impaired inhibitory function.

Age-Dependent Activation of Purinergic Transmission Contributes to the Development of Epileptogenesis in ADSHE Model Rats

To explore the developmental processes of epileptogenesis/ictogenesis, this study determined age-dependent functional abnormalities associated with purinergic transmission in a genetic rat model (S286L-TG) of autosomal-dominant sleep-related hypermotor epilepsy (ADSHE). The age-dependent fluctuations in the release of ATP and L-glutamate in the orbitofrontal cortex (OFC) were determined using microdialysis and ultra-high-performance liquid chromatography with mass spectrometry (UHPLC-MS). ATP release from cultured astrocytes was also determined using UHPLC-MS. The expressions of P2X7 receptor (P2X7R), connexin 43, phosphorylated-Akt and phosphorylated-Erk were determined using capillary immunoblotting. No functional abnormalities associated with purinergic transmission could be detected in the OFC of 4-week-old S286L-TG and cultured S286L-TG astrocytes. However, P2X7R expression, as well as basal and P2X7R agonist-induced ATP releases, was enhanced in S286L-TG OFC in the critical ADSHE seizure onset period (7-week-old). Long-term exposure to a modest level of P2X7R agonist, which could not increase astroglial ATP release, for 14 d increased the expressions of P2X7R and connexin 43 and the signaling of Akt and Erk in astrocytes, and it enhanced the sensitivity of P2X7R to its agonists. Akt but not Erk increased P2X7R expression, whereas both Akt and Erk increased connexin 43 expression. Functional abnormalities, enhanced ATP release and P2X7R expression were already seen before the onset of ADSHE seizure in S286L-TG. Additionally, long-term exposure to the P2X7R agonist mimicked the functional abnormalities associated with purinergic transmission in astrocytes, similar to those in S286L-TG OFC. Therefore, these results suggest that long-term modestly enhanced purinergic transmission and/or activated P2X7R are, at least partially, involved in the development of the epileptogenesis of ADSHE, rather than that of ictogenesis.

Age-Dependent Activation of Pannexin1 Function Contributes to the Development of Epileptogenesis in Autosomal Dominant Sleep-related Hypermotor Epilepsy Model Rats

To explore the processes of epileptogenesis/ictogenesis, this study determined the age-dependent development of the functional abnormalities in astroglial transmission associated with pannexin1-hemichannel using a genetic rat model of autosomal dominant sleep-related hypermotor epilepsy (ADSHE) named 'S286L-TG'. Pannexin1 expression in the plasma membrane of primary cultured cortical astrocytes and the orbitofrontal cortex (OFC), which is an ADSHE focus region, were determined using capillary immunoblotting. Astroglial D-serine releases induced by artificial high-frequency oscillation (HFO)-evoked stimulation, the removal of extracellular Ca2+, and the P2X7 receptor agonist (BzATP) were determined using ultra-high performance liquid chromatography (UHPLC). The expressions of pannexin1 in the plasma membrane fraction of the OFC in S286L-TG at four weeks old were almost equivalent when compared to the wild type. The pannexin1 expression in the OFC of the wild type non-statistically decreased age-dependently, whereas that in S286L-TG significantly increased age-dependently, resulting in relatively increasing pannexin1 expression from the 7- (at the onset of interictal discharge) and 10-week-old (after the ADSHE seizure onset) S286L-TG compared to the wild type. However, no functional abnormalities of astroglial pannexin1 expression or D-serine release through the pannexin1-hemichannels from the cultured astrocytes of S286L-TG could be detected. Acutely HFO-evoked stimulation, such as physiological ripple burst (200 Hz) and epileptogenic fast ripple burst (500 Hz), frequency-dependently increased both pannexin1 expression in the astroglial plasma membrane and astroglial D-serine release. Neither the selective inhibitors of pannexin1-hemichannel (10PANX) nor connexin43-hemichannel (Gap19) affected astroglial D-serine release during the resting stage, whereas HFO-evoked D-serine release was suppressed by both inhibitors. The inhibitory effect of 10PANX on the ripple burst-evoked D-serine release was more predominant than that of Gap19, whereas fast ripple burst-evoked D-serine release was predominantly suppressed by Gap19 rather than 10PANX. Astroglial D-serine release induced by acute exposure to BzATP was suppressed by 10PANX but not by Gap19. These results suggest that physiological ripple burst during the sleep spindle plays important roles in the organization of some components of cognition in healthy individuals, but conversely, it contributes to the initial development of epileptogenesis/ictogenesis in individuals who have ADSHE vulnerability via activation of the astroglial excitatory transmission associated with pannexin1-hemichannels.

Impact of the Japanese Government's 'General Principles of Suicide Prevention Policy' on youth suicide from 2007 to 2022

BACKGROUND

The Japanese Government programme 'General Principles of Suicide Prevention Policy' (GPSPP) contributed to decreasing suicide mortality rates (SMRs) before the COVID-19 pandemic, but they increased after the pandemic.

AIMS

To identify risk factors for youth suicide and the impact of GPSPP on youth suicide.

METHOD

Annual suicide numbers during 2007-2022 were obtained from government databases. SMRs of student and non-student youths were analysed with a linear mixed-effects model. Interrupted time-series analysis was conducted to investigate temporal relations between three GPSPP periods and SMRs with 52 suicide motives among high school, special vocational school and university students. Multiple regression analysis was conducted to investigate the influence of grade repetition on university student SMRs.

RESULTS

Non-student youth SMRs were higher than student SMRs. School-related (worrying about the future/underachievement), health-related (mainly mental illness) and family-related (conflict with parent and severe verbal reprimands) motives were major motives for student SMRs. During the first GPSPP period (2007-2012), no student SMRs decreased. During the second period (2012-2017), university and special vocational school student SMRs increased, but high school student SMRs were unchanged. In contrast, during the third period (2017-2022), with the exception of male special vocational school students, all SMRs increased. Unexpectedly, long-term grade repetition was negatively associated with health-related SMRs.

CONCLUSIONS

These findings suggest that GPSPP-supported programmes in schools partially contributed to student suicide prevention. To suppress increasing student SMRs, social/life support specialists should participate in in-school support services to bolster the social standing and lives of students who repeat grades or experience setbacks.

Trends in Suicidal Mortality and Motives among Working-Ages Individuals in Japan during 2007-2022

Suicides in Japan consistently decreased from 2009-2019, but increased during the COVID-19 pandemic. To identify causes of increasing suicides, age-dependent and temporal fluctuations of suicide mortality rate per 100,000 (SMRP) in working-age generations (20-59 years) disaggregated by suicidal motives (7-categories; 52-subcategories) and sex from 2007 to 2022, were analyzed by analysis of variance and joinpoint regression, respectively, using the government suicide database "Suicide Statistics". The SMRP of 20-29 year-old males and 20-49 year-old females began to increase in the late 2010s. SMRPs of these high-risk groups for suicides caused by depression (the leading suicidal motive for all groups) began increasing in the late 2010s. Economic-related, employment-related, and romance-related problems contributed to the increasing SMRPs in 20-29 males in the late 2010s. Romance-related and family-related problems contributed to the increasing SMRPs of 20-29 females in the late 2010s. Increasing SMRPs caused by child-raising stress in 20-39 year-old females from the late 2010s was a remarkable finding. In contrast, SMRPs of 30-59 year-old males consistently decreased until 2021; however, in these groups, SMRPs for suicides caused by various motives sharply increased in 2022. The consistent increase in SMRPs of high-risk groups from the late 2010s to the pandemic suggest recent socioeconomic and psychosocial problems in Japan possibly contributed to the increasing SMRPs in these high-risk groups independently of pandemic-associated factors, whereas the SMRPs of males of 30-59 years were probably associated with the ending of the pandemic rather than pandemic-associated factors.

Impacts of Complete Unemployment Rates Disaggregated by Reason and Duration on Suicide Mortality from 2009-2022 in Japan

In Japan, suicides had consistently decreased before the COVID-19 pandemic (from 2009-2019), but conversely increased after the pandemic outbreak (from 2020-2022). To identify the features of fluctuations of suicides in Japan, the standardized suicide mortality rates per 100,000 population (SMRP) disaggregated by gender (males/females) and age (10-year cohorts) from 2009-2022 were analyzed using interrupted time-series and joinpoint regression analyses. Temporal causalities from unemployment rate (CUR) disaggregated by unemployment duration and reasons for seeking work to SMRP were analyzed using vector autoregressive modelling with Granger causality analysis. SMRP fluctuations from 2009-2022 were composed of three patterns, such as positive discontinuity (increasing) synchronized with the pandemic outbreak, attenuations of decreasing trends before the pandemic, turning from decreasing before the pandemic to increasing/unchanging after the pandemic outbreak. Dismissal CUR positively related to SMRP of working-age generations, whereas voluntary CUR negatively related to SMRP of younger population (<30 years), which turned to persistently increasing before the pandemic (approximately 2016-2017). CUR shorter than 3 months positively related to SMRP of working-age females, which displayed promptly increasing synchronization with the pandemic outbreak. CUR longer than 12 months positively related to SMRP of working-age males, which contributed to persistently increasing SMRPs during the pandemic. These results suggest that increasing SMRP during 2020-2022 in Japan has been probably at-tributed to interactions among the pandemic-related factors, continuous vulnerabilities from before the pandemic and newly developing risk factors for suicides during the pandemic. Unexpectedly, increasing SMRPs of working-age males in 2022 suggest that either prolongation of the pandemic or the ending of the pandemic might positively affect suicides in Japan.

A Novel Gliotransmitter, L-β-Aminoisobutyric Acid, Contributes to Pathophysiology of Clinical Efficacies and Adverse Reactions of Clozapine

Clozapine is listed as one of the most effective antipsychotics and has been approved for treating treatment-resistant schizophrenia (TRS); however, several type A and B adverse reactions, including weight gain, metabolic complications, cardiotoxicity, convulsions, and discontinuation syndromes, exist. The critical mechanisms of clinical efficacy for schizophrenia, TRS, and adverse reactions of clozapine have not been elucidated. Recently, the GABA isomer L-β-aminoisobutyric acid (L-BAIBA), a protective myokine in the peripheral organs, was identified as a candidate novel transmission modulator in the central nervous system (CNS). L-BAIBA activates adenosine monophosphate-activated protein kinase (AMPK) signalling in both the peripheral organs and CNS. Activated AMPK signalling in peripheral organs is an established major target for treating insulin-resistant diabetes, whereas activated AMPK signalling in the hypothalamus contributes to the pathophysiology of weight gain and metabolic disturbances. Clozapine increases L-BAIBA synthesis in the hypothalamus. In addition, the various functions of L-BAIBA in the CNS have recently been elucidated, including as an activator of GABA-B and group-III metabotropic glutamate (III-mGlu) receptors. Considering the expressions of GABA-B and III-mGlu receptors (localised in the presynaptic regions), the activation of GABA-B and III-mGlu receptors can explain the distinct therapeutic advantages of clozapine in schizophrenia or TRS associated with N-methyl-D-aspartate (NMDA) receptor disturbance compared with other atypical antipsychotics via the inhibition of the persistent tonic hyperactivation of thalamocortical glutamatergic transmission in the prefrontal cortex. L-BAIBA has also been identified as a gliotransmitter, and a detailed exploration of the function of L-BAIBA in tripartite synaptic transmission can further elucidate the pathophysiology of effectiveness for treating TRS and/or specific adverse reactions of clozapine.

Effect of an Internet-Delivered Cognitive Behavioral Therapy-Based Sleep Improvement App for Shift Workers at High Risk of Sleep Disorder: Single-Arm, Nonrandomized Trial

BACKGROUND

Shift workers are at high risk of developing sleep disorders such as shift worker sleep disorder or chronic insomnia. Cognitive behavioral therapy (CBT) is the first-line treatment for insomnia, and emerging evidence shows that internet-based CBT is highly effective with additional features such as continuous tracking and personalization. However, there are limited studies on internet-based CBT for shift workers with sleep disorders.

OBJECTIVE

This study aimed to evaluate the impact of a 4-week, physician-assisted, internet-delivered CBT program incorporating machine learning-based well-being prediction on the sleep duration of shift workers at high risk of sleep disorders. We evaluated these outcomes using an internet-delivered CBT app and fitness trackers in the intensive care unit.

METHODS

A convenience sample of 61 shift workers (mean age 32.9, SD 8.3 years) from the intensive care unit or emergency department participated in the study. Eligible participants were on a 3-shift schedule and had a Pittsburgh Sleep Quality Index score ≥5. The study comprised a 1-week baseline period, followed by a 4-week intervention period. Before the study, the participants completed questionnaires regarding the subjective evaluation of sleep, burnout syndrome, and mental health. Participants were asked to wear a commercial fitness tracker to track their daily activities, heart rate, and sleep for 5 weeks. The internet-delivered CBT program included well-being prediction, activity and sleep chart, and sleep advice. A job-based multitask and multilabel convolutional neural network-based model was used for well-being prediction. Participant-specific sleep advice was provided by sleep physicians based on daily surveys and fitness tracker data. The primary end point of this study was sleep duration. For continuous measurements (sleep duration, steps, etc), the mean baseline and week-4 intervention data were compared. The 2-tailed paired t test or Wilcoxon signed rank test was performed depending on the distribution of the data.

RESULTS

In the fourth week of intervention, the mean daily sleep duration for 7 days (6.06, SD 1.30 hours) showed a statistically significant increase compared with the baseline (5.54, SD 1.36 hours; P=.02). Subjective sleep quality, as measured by the Pittsburgh Sleep Quality Index, also showed statistically significant improvement from baseline (9.10) to after the intervention (7.84; P=.001). However, no significant improvement was found in the subjective well-being scores (all P>.05). Feature importance analysis for all 45 variables in the prediction model showed that sleep duration had the highest importance.

CONCLUSIONS

The physician-assisted internet-delivered CBT program targeting shift workers with a high risk of sleep disorders showed a statistically significant increase in sleep duration as measured by wearable sensors along with subjective sleep quality. This study shows that sleep improvement programs using an app and wearable sensors are feasible and may play an important role in preventing shift work-related sleep disorders.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.2196/24799.

Suicidal Mortality and Motives Among Middle-School, High-School, and University Students

IMPORTANCE

The suicide mortality rate per 100 000 population (SMRP) consistently decreased before the COVID-19 pandemic outbreak in Japan and then unexpectedly increased during the pandemic. However, the underlying mechanisms remain poorly understood.

OBJECTIVE

To identify trends in and factors associated with suicidal mortality and motives among students in Japan from 2007 to 2022.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, data on SMRPs among Japanese middle-school, high-school, and university students were obtained from the government suicide database Suicide Statistics of the National Police Agency.

MAIN OUTCOMES AND MEASURES

Age-dependent and temporal fluctuations in annual SMRPs, disaggregated by suicidal motive (7 categories and 52 subcategories), sex, and school, were analyzed using linear mixed-effect and joinpoint regression models, respectively.

RESULTS

Total suicide numbers from 2007 to 2022 were as follows: 760 male middle-school students, 635 female middle-school students, 2376 male high-school students, 1566 female high-school students, 5179 male university students, and 1880 female university students. The mean (SD) student populations from 2007 to 2022 were as follows: 1 752 737 (81 334) male middle-school students, 1 675 572 (78 824) female middle-school students, 1 648 274 (67 520) male high-school students, 1 614 828 (60 032) female high-school students, 1 652 689 (32 724) male university students, and 1 229 142 (57 484) female university students. Among male students, the leading motives were school-related factors (underachievement and worrying about the future), followed by family-related and health-related motives. Among female students, school-related and family-related motives decreased, but health-related motives showed an age-dependent increase. The SMRPs of middle-school male students and female students were almost equal (mean [SD], 2.7 [1.0] vs 2.4 [1.4]), but the age-dependent increase in SMRPs among male students was pronounced (mean [SD], high-school vs university male students, 9.1 [2.4] vs 19.6 [3.0]; high-school vs university female students, 6.1 [2.4] vs 9.6 [1.8]). However, the incidence of suicide among high-school students associated with health-related motives was greater in female students. The majority of suicides associated with major impactable suicidal motives (school-related, health-related, and family-related motives) began increasing before the pandemic. Changes in SMRP associated with interpersonal relationships, such as conflict with classmates or parents, were not significant, but the rates increased greatly during the pandemic.

CONCLUSIONS AND RELEVANCE

School-related, health-related, and family-related problems were major motives, whereas the impacts of health-related and family-related motives increased and decreased with age, respectively. Notably, most SMRPs associated with major impactable motives (underachievement, conflict with a parent or classmate, and mental illnesses) had already begun increasing in the late 2010s, indicating that recent increasing SMRPs among school-aged individuals were associated with pandemic-related factors and other factors affecting this generation before the pandemic. It may be inappropriate to uniformly apply research findings based on school-aged individuals to school-based suicide prevention programs for students in middle school, high school, and university.

Enhanced L-β-Aminoisobutyric Acid Is Involved in the Pathophysiology of Effectiveness for Treatment-Resistant Schizophrenia and Adverse Reactions of Clozapine

Clozapine is an effective antipsychotic for the treatment of antipsychotic-resistant schizophrenia; however, specific types of A/B adverse effects and clozapine-discontinuation syndromes are also well known. To date, both the critical mechanisms of clinical actions (effective for antipsychotic-resistant schizophrenia) and the adverse effects of clozapine remain to be elucidated. Recently, we demonstrated that clozapine increased the synthesis of L-β-aminoisobutyric acid (L-BAIBA) in the hypothalamus. L-BAIBA is an activator of the adenosine monophosphate-activated protein kinase (AMPK), glycine receptor, GABA_A receptor, and GABA_B receptor (GABA_B-R). These targets of L-BAIBA overlap as potential targets other than the monoamine receptors of clozapine. However, the direct binding of clozapine to these aminoacidic transmitter/modulator receptors remains to be clarified. Therefore, to explore the contribution of increased L-BAIBA on the clinical action of clozapine, this study determined the effects of clozapine and L-BAIBA on tripartite synaptic transmission, including GABA_B-R and the group-III metabotropic glutamate receptor (III-mGluR) using cultured astrocytes, as well as on the thalamocortical hyper-glutamatergic transmission induced by impaired glutamate/NMDA receptors using microdialysis. Clozapine increased astroglial L-BAIBA synthesis in time/concentration-dependent manners. Increased L-BAIBA synthesis was observed until 3 days after clozapine discontinuation. Clozapine did not directly bind III-mGluR or GABA_B-R, whereas L-BAIBA activated these receptors in the astrocytes. Local administration of MK801 into the reticular thalamic nucleus (RTN) increased L-glutamate release in the medial frontal cortex (mPFC) (MK801-evoked L-glutamate release). Local administration of L-BAIBA into the mPFC suppressed MK801-evoked L-glutamate release. These actions of L-BAIBA were inhibited by antagonists of III-mGluR and GABA_B-R, similar to clozapine. These in vitro and in vivo analyses suggest that increased frontal L-BAIBA signaling likely plays an important role in the pharmacological actions of clozapine, such as improving the effectiveness of treating treatment-resistant schizophrenia and several clozapine discontinuation syndromes via the activation of III-mGluR and GABA_B-R in the mPFC.

A Candidate Gliotransmitter, L-β-Aminoisobutyrate, Contributes to Weight Gain and Metabolic Complication Induced by Atypical Antipsychotics

Lurasidone and quetiapine are effective atypical mood-stabilizing antipsychotics, but lurasidone and quetiapine are listed as lower-risk and high-risk for weight gain/metabolic complications, respectively. The pathophysiology of the discrepancy of metabolic adverse reactions between these antipsychotics remains to be clarified. The GABA isomer, β-aminoisobutyric acid (BAIBA) enantiomer, was recently re-discovered as myokine via an AMP-activated protein kinase activator (AMPK) enhancer and inhibitory gliotransmitter. Notably, activation of AMPK in peripheral organs improves, but in the hypothalamus, it aggravates metabolic disturbances. Therefore, we determined effects of chronic administration of lurasidone and quetiapine on intracellular and extracellular levels of the BAIBA enantiomer. L-BAIBA is a major BAIBA enantiomer in the hypothalamus and astrocytes, whereas L-BAIBA only accounted for about 5% of total plasma BAIBA enantiomers. Chronic lurasidone administration did not affect body weight but decreased the L-BAIBA level in hypothalamus and cultured astrocytes, whereas chronic quetiapine administration increased body weight and the L-BAIBA level in hypothalamus and astrocytes. Contrary, neither lurasidone nor quetiapine affected total plasma levels of the BAIBA enantiomer since D-BAIBA levels were not affected by these antipsychotics. These results suggest that activation of intracellular L-BAIBA signaling is, at least partially, involved in the pathophysiology of metabolic adverse reaction of quetiapine. Furthermore, this study also demonstrated that lurasidone and quetiapine suppressed and enhanced astroglial L-BAIBA release induced by ripple-burst stimulation (which physiologically contributes to cognitive memory integration during sleep), respectively. Therefore, L-BAIBA probably contributes to the pathophysiology of not only metabolic adverse reactions, but also a part of clinical action of lurasidone or quetiapine.

Analyzing the changing relationship between personal consumption and suicide mortality during COVID-19 pandemic in Japan, using governmental and personal consumption transaction databases

During the early stages of the ongoing COVID-19 pandemic, suicides did not increase in most countries/regions. Japan, however, was an exception to this, reporting increased numbers of female suicides with no changes in male suicide. To explore the trends of increasing suicides, the fluctuations of personal consumption (as an indicator of lifestyle) and standardized suicide death rate (SDR) disaggregated by age, sex, and prefecture, were determined using a linear mixed-effect model. Additionally, fixed effects of personal consumption on SDR during the pandemic were also analyzed using hierarchical linear regression models with robust standard errors. During the first wave of the pandemic, SDR for both sexes decreased slightly but increased during the second half of 2020. SDR of females younger than 70 years old and males younger than 40 years old continued to increase throughout 2021, whereas SDR for other ages of both sexes did not increase. Personal consumption expenditures on out-of-home recreations (travel agencies, pubs, and hotels) and internet/mobile communication expenses decreased, but expenditures on home-based recreations (contents distribution) increased during the pandemic. Increased expenditures on internet/mobile communication were related to increasing SDR of both sexes. Increasing expenditures on content distributions were related to increasing females' SDR without affecting that of males. Decreasing expenditures on pubs were related to increasing SDR of both sexes in the non-metropolitan region. These findings suggest that transformed individual lifestyles, extended time at home with a decreased outing for contact with others, contributed to the progression of isolation as a risk of suicide. Unexpectedly, increasing compensatory contact with others using internet/mobile communication enhanced isolation resulting in increased suicide risk.

Dose-Dependent Biphasic Action of Quetiapine on AMPK Signalling via 5-HT7 Receptor: Exploring Pathophysiology of Clinical and Adverse Effects of Quetiapine

Recent pharmacological studies indicated that the modulation of tripartite-synaptic transmission plays important roles in the pathophysiology of schizophrenia, mood disorders and adverse reactions. Therefore, to explore the mechanisms underlying the clinical and adverse reactions to atypical antipsychotics, the present study determined the effects of the sub-chronic administration of quetiapine (QTP: 3~30 μM) on the protein expression of 5-HT7 receptor (5-HT7R), connexin43 (Cx43), cAMP level and intracellular signalling, Akt, Erk and adenosine monophosphate-activated protein kinase (AMPK) in cultured astrocytes and the rat hypothalamus, using ultra-high-pressure liquid chromatography with mass spectrometry and capillary immunoblotting systems. QTP biphasically increased physiological ripple-burst evoked astroglial D-serine release in a concentration-dependent manner, peaking at 10 μM. QTP enhanced the astroglial signalling of Erk concentration-dependently, whereas both Akt and AMPK signalling’s were biphasically enhanced by QTP, peaking at 10 μM and 3 μM, respectively. QTP downregulated astroglial 5-HT7R in the plasma membrane concentration-dependently. Protein expression of Cx43 in astroglial cytosol and intracellular cAMP levels were decreased and increased by QTP also biphasically, peaking at 3 μM. The dose-dependent effects of QTP on the protein expression of 5-HT7R and Cx43, AMPK signalling and intracellular cAMP levels in the hypothalamus were similar to those in astrocytes. These results suggest several complicated pharmacological features of QTP. A therapeutically relevant concentration/dose of QTP activates Akt, Erk and AMPK signalling, whereas a higher concentration/dose of QTP suppresses AMPK signalling via its low-affinity 5-HT7R inverse agonistic action. Therefore, 5-HT7R inverse agonistic action probably plays important roles in the prevention of a part of adverse reactions of QTP, such as weight gain and metabolic complications.

Bidirectional Causality between Spreading COVID-19 and Individual Mobilisation with Consumption Motives across Prefectural Borders in Japan

A combination of pharmaceutical and non-pharmaceutical interventions as well as social restrictions has been recommended to prevent the spread of coronavirus disease 2019 (COVID-19). Therefore, social contact surveys play an essential role as the basis for more effective measures. This study attempts to explore the fundamental basis of the expansion of COVID-19. Temporal bidirectional causalities between the numbers of newly confirmed COVID-19 cases (NCCC) and individual mobilisations with consumption motives across prefecture borders in three metropolitan regions in Japan were analysed using vector autoregression models. Mobilisation with consumption in pubs from Kanto to Tokai contributed to the spread of COVID-19 in both regions. Meanwhile, causal mobilisation with consumption motives in Kansai also contributed to the expansion of COVID-19; however, the pattern was dependent on the industrial characteristics of each prefecture in Kansai. Furthermore, the number of pub visitors in Kanto immediately decreased when NCCC increased in Kanto. In contrast, the causal mobilisations for the expansion of COVID-19 in the Tokai and Kansai regions were unaffected by the increasing NCCC. These findings partially proved the validity of the conventional governmental measures to suppress pub visitors across prefectural borders. Nevertheless, the individual causal mobilisations with consumption motives that contributed to the increasing COVID-19 cases are not identical nationwide, and thus, regional characteristics should be considered when devising preventive strategies.

Catechol-O-methyltransferase (COMT) Val158Met Polymorphism and Prepulse Inhibition of the Change-related Cerebral Response

Change-related potentials elicited by an abrupt sound feature's change are attenuated by a leading weak sound (prepulse inhibition: PPI). We investigated whether the PPI index is associated with the catechol-methyltransferase (COMT) Val158Met polymorphism (rs4680), which is involved in the metabolism of dopamine in the prefrontal cortex. Healthy subjects with normal hearing were recruited (n = 70). A train of 100-Hz clicks 650 ms in duration was used. The test stimulus was an abrupt increase in sound intensity (+10 dB) from the baseline (70 dB) provided at 400 ms after the sound onset. Three consecutive clicks at 30, 40, and 50 ms before the change's onset were greater (+3 or +5 dB) from the baseline as a prepulse. The targeting auditory evoked potential component was Change-N1 peaking approx. 130 ms after the change onset. We calculated the inhibition level as the% inhibition of the Change-N1 amplitude by a prepulse. The %PPI in the Met-carriers was significantly greater than that in the Val/Val-individuals. Our results suggest that dopamine might play a role in the PPI of the change-related response. We propose that this index has the potential to identify an intermediate phenotype in psychiatric disorders such as schizophrenia.

Exploring characteristics of increased suicide during the COVID-19 pandemic in Japan using provisional governmental data

Background

The Japanese age-standardised death rate of suicide (SDR) had decreased during 2009-2019, but increased in 2020-2021, during the COVID-19 pandemic.

Methods

This study aimed to explain the trend change in the SDR during the pandemic, disaggregated by prefecture, gender, suicide method and household, as compared to predicted SDR derived from pre-pandemic data, using linear mixed-effect and hierarchical linear regression models with robust standard error analyses.

Findings

The SDR was lower during March-June 2020 (during the first wave of the pandemic), but higher during July-December 2020 than the predicted SDR. In 2021, males' SDR was nearly equal to the predicted SDR, whereas females' SDR in the metropolitan-region (17.5%: 95% confidence interval: 13.9-21.2%) and non-metropolitan-region (24.7%: 95% confidence interval: 22.8-26.7%) continued to be higher than the predicted SDR. These gender- and region-dependent temporal fluctuations of SDR were synchronised with those of SDRs caused by hanging, at home and single-person-households. Additionally, the rising number of infected patients with the SARS-CoV-2 and polymerase chain reaction (PCR) diagnostic examinations were positively (β = 0.024) and negatively (β =-0.002) related to the SDR during the pandemic, respectively.

Interpretation

Japanese suicide statistics have previously established that the predominant method and place of suicide were by hanging and at the individual's home, respectively. The present findings suggest that transformed lifestyles during the pandemic, increasing time spent at home, enhanced the suicide risk of Japanese people by hanging and at home.

Funding

Regional Suicide Countermeasures Emergency Enhancement Fund of Mie Prefecture (2021-40).

Brexpiprazole Reduces 5-HT7 Receptor Function on Astroglial Transmission Systems

Several atypical antipsychotics exert mood-stabilising effects via the modulation of various monoamine receptors and intracellular signallings. Recent pharmacodynamic studies suggested that tripartite synaptic transmission can contribute to the pathophysiology of schizophrenia and mood disorders, their associated cognitive impairment, and several adverse reactions to atypical antipsychotics. Therefore, to explore the mechanisms underlying the antidepressive mood-stabilising and antipsychotic effects of brexpiprazole (Brex), we determined the effects of subchronic administration of therapeutically relevant concentrations/doses of Brex on the protein expression of 5-HT receptors, connexin43, cAMP levels, and intracellular signalling in cultured astrocytes and rat hypothalamus using ultra-high-pressure liquid chromatography with mass spectrometry and capillary immunoblotting systems. Subchronic administration of a therapeutically relevant concentration of Brex (300 nM) downregulated both 5-HT1A (5-HT1AR) and 5-HT7 (5-HT7R) receptors, in addition to phosphorylated Erk (pErk), without affecting phosphorylated Akt in the astroglial plasma membrane. Subchronic administration of 300 nM Brex decreased and increased phosphorylated AMPK and connexin43, respectively, in the astroglial cytosol fraction. A therapeutically relevant concentration of Brex acutely decreased the astroglial cAMP level, whereas, under the inhibition of 5-HT1AR, Brex did not affect astroglial cAMP levels. However, the 5-HT7R-agonist-induced increased astroglial cAMP level was inhibited by Brex. In contrast to the in vitro study, systemic subchronic administration of effective doses of Brex (3 and 10 mg/kg/day for 14 days) increased the cAMP level but did not affect phosphorylated AMPK in the rat hypothalamus. These results suggest several complicated pharmacological features of Brex. Partial 5-HT1AR agonistic action predominates in the low range of therapeutically relevant concentrations of Brex, whereas in the high range, 5-HT7R inverse agonist-like action is overlapped on the 5-HT1A agonistic action. These unique suppressive effects of Brex on 5-HT7R play important roles in the clinical features of Brex regarding its antidepressive mood-stabilising actions.

Impact of 5-HT7 receptor inverse agonism of lurasidone on monoaminergic tripartite synaptic transmission and pathophysiology of lower risk of weight gain

A part of atypical antipsychotics exert mood-stabilising effects via modulation of various monoamine receptors and intracellular signalling. Recent pharmacodynamic studies suggested that tripartite-synaptic transmission can be involved in pathophysiology of mood-disorders, schizophrenia, their associated cognitive impairments, and several adverse-reactions to atypical antipsychotics. Therefore, to explore mechanisms underlying antidepressive mood-stabilising and antipsychotic effects of lurasidone, we determined concentration-dependent effects of acute and subchronic lurasidone administrations on astroglial L-glutamate release, and expression of connexin43, ERK, AKT, adenosine monophosphate activated protein kinase (AMPK), 5-HT1A (5-HT1AR) and 5-HT7 (5-HT7R) receptors in cultured astrocytes using ultra-high-pressure liquid-chromatography with mass-spectrometry and capillary-immunoblotting systems. Therapeutically-relevant lurasidone concentration suppressed astroglial L-glutamate release through activated connexin43-containing hemichannel by decreasing connexin43 expression in plasma-membrane. Subchronic lurasidone administration downregulated 5-HT1AR and 5-HT7R in astroglial plasma-membrane concentration-dependently. Subchronic lurasidone administration attenuated ERK and AMPK signallings concentration-dependently without affecting AKT signalling. These results suggest that effects of subchronic lurasidone administration on astroglial L-glutamate release, 5-HT receptor, and intracellular signalling are similar to vortioxetine and different from mood-stabilising atypical antipsychotics, clozapine. Therefore, inhibitory effects of subchronic lurasidone administration on astroglial L-glutamate release through activated connexin43-containing hemichannel probably contribute to pathophysiology of antidepressive mood-stabilising effects of lurasidone. Furthermore, inhibitory effects of subchronic lurasidone administration on ERK and AMPK activities (without affecting AKT activity) induced by downregulation of 5-HT7R could result in clinical advantages of lurasidone, lower risk of weight gain.

Effects of Magnitude of Leading Stimulus on Prepulse Inhibition of Auditory Evoked Cerebral Responses: An Exploratory Study

An abrupt change in a sound feature (test stimulus) elicits a specific cerebral response, which is attenuated by a weaker sound feature change (prepulse) preceding the test stimulus. As an exploratory study, we investigated whether and how the magnitude of the change of the prepulse affects the degree of prepulse inhibition (PPI). Sound stimuli were 650 ms trains of clicks at 100 Hz. The test stimulus was an abrupt sound pressure increase (by 10 dB) in the click train. Three consecutive clicks, weaker (−5 dB, −10 dB, −30 dB, or gap) than the baseline, at 30, 40, and 50 ms before the test stimulus, were used as prepulses. Magnetic responses to the ten types of stimuli (test stimulus alone, control, four types of tests with prepulses, and four types of prepulses alone) were recorded in 10 healthy subjects. The change-related N1m component, peaking at approximately 130 ms, and its PPI were investigated. The degree of PPI caused by the −5 dB prepulse was significantly weaker than that caused by other prepulses. The degree of PPI caused by further decreases in prepulse magnitude showed a plateau level between the −10 dB and gap prepulses. The results suggest that there is a physiologically significant range of sensory changes for PPI, which plays a role in the change detection for survival.

Internet-Based Individualized Cognitive Behavioral Therapy for Shift Work Sleep Disorder Empowered by Well-Being Prediction: Protocol for a Pilot Study

Background

Shift work sleep disorders (SWSDs) are associated with the high turnover rates of nurses, and are considered a major medical safety issue. However, initial management can be hampered by insufficient awareness. In recent years, it has become possible to visualize, collect, and analyze the work-life balance of health care workers with irregular sleeping and working habits using wearable sensors that can continuously monitor biometric data under real-life settings. In addition, internet-based cognitive behavioral therapy for psychiatric disorders has been shown to be effective. Application of wearable sensors and machine learning may potentially enhance the beneficial effects of internet-based cognitive behavioral therapy.

Objective

In this study, we aim to develop and evaluate the effect of a new internet-based cognitive behavioral therapy for SWSD (iCBTS). This system includes current methods such as medical sleep advice, as well as machine learning well-being prediction to improve the sleep durations of shift workers and prevent declines in their well-being.

Methods

This study consists of two phases: (1) preliminary data collection and machine learning for well-being prediction; (2) intervention and evaluation of iCBTS for SWSD. Shift workers in the intensive care unit at Mie University Hospital will wear a wearable sensor that collects biometric data and answer daily questionnaires regarding their well-being. They will subsequently be provided with an iCBTS app for 4 weeks. Sleep and well-being measurements between baseline and the intervention period will be compared.

Results

Recruitment for phase 1 ended in October 2019. Recruitment for phase 2 has started in October 2020. Preliminary results are expected to be available by summer 2021.

Conclusions

iCBTS empowered with well-being prediction is expected to improve the sleep durations of shift workers, thereby enhancing their overall well-being. Findings of this study will reveal the potential of this system for improving sleep disorders among shift workers.

Trial Registration

UMIN Clinical Trials Registry UMIN000036122 (phase 1), UMIN000040547 (phase 2); https://tinyurl.com/dkfmmmje, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046284

International Registered Report Identifier (IRRID)

DERR1-10.2196/24799

Electrical field distribution of Change-N1 and its prepulse inhibition

An abrupt change in a sound feature (Test) in a continuous sound elicits an auditory evoked potential, peaking at approx. 100-180 ms (Change-N1) after the change onset. Change-N1 is attenuated by a preceding weak change stimulus (Prepulse), in the phenomenon known as prepulse inhibition (PPI). In this electroencephalographic study, we compared these two indexes among scalp electrodes. Change-N1 was elicited by an abrupt 10-dB increase in sound pressure in repeats of a 70-dB click sound at 100 Hz and was recorded using 22 electrodes in 31 healthy subjects. The prepulse was a 10-dB decrease in three consecutive clicks at 30, 40, and 50 ms before the Test onset. Four stimuli (Test alone, Test with Prepulse, Prepulse alone, and background alone) were presented randomly through headphones at an even probability. The results demonstrated that: (1) Electrodes at the frontal/central midline were reconfirmed to be suitable to record Change-N1; (2) Change-N1 showed right-hemisphere predominance; (3) There was no difference in the %PPI among regions (prefrontal/frontal/central) and hemispheres (midline/left/right); and (4) the Change-N1 amplitude and its PPI at prefrontal electrodes were positively correlated with those at the frontal electrodes. These results support the use of Change-N1 and its PPI as a tool to evaluate the change detection sensitivity and inhibitory function in individuals. The use of prefrontal electrodes can be an option for a screening test.

The Auditory Steady-State Response: Electrophysiological Index for Sensory Processing Dysfunction in Psychiatric Disorders

Sensory processing is disrupted in several psychiatric disorders, including schizophrenia, bipolar disorder, and autism spectrum disorder. In this review, we focus on the electrophysiological auditory steady-state response (ASSR) driven by high-frequency stimulus trains as an index for disease-associated sensory processing deficits. The ASSR amplitude is suppressed within the gamma band (≥30 Hz) among these patients, suggesting an imbalance between GABAergic and N-methyl-D-aspartate (NMDA) receptor-mediated neurotransmission. The reduced power and synchronization of the 40-Hz ASSR are robust in patients with schizophrenia. In recent years, similar ASSR deficits at gamma frequencies have also been reported in patients with bipolar disorder and autism spectrum disorder. We summarize ASSR abnormalities in each of these psychiatric disorders and suggest that the observed commonalities reflect shared pathophysiological mechanisms. We reviewed studies on phase resetting in which a salient sensory stimulus affects ASSR. Phase resetting induces the reduction of both the amplitude and phase of ASSR. Moreover, phase resetting is also affected by rare auditory stimulus patterns or superimposed stimuli of other modalities. Thus, sensory memory and multisensory integration can be investigated using phase resetting of ASSR. Here, we propose that ASSR amplitude, phase, and resetting responses are sensitive indices for investigating sensory processing dysfunction in psychiatric disorders.

Weaker prepulse exerts stronger suppression of a change-detecting neural circuit

Change-N1 peaking 90-180 ms after changes in a sound feature of a continuous sound is clearly attenuated by a preceding change stimulus (called a "prepulse"). Here, we investigated the effects of a preceding decrease in sound pressure on the degree of inhibition of the subsequent Change-N1 amplitude. Using 100-Hz click train sounds, we obtained Change-N1s from 11 healthy volunteers. The two types of test stimuli were an abrupt 10-dB increase from the baseline (70 dB) and the insertion of a 0.45-ms inter-aural time difference in the middle of the sound. Three consecutive clicks at 30, 40, and 50 ms before the change onset that was used as a prepulse were weaker than the background by 5 or 10 dB. The Change-N1 elicited by the two test stimuli was attenuated more strongly by the weaker prepulse, which was not congruent with the theory that the inhibition of the subsequent sensory/sensory-motor processing depends on the sound pressure level of a prepulse. These results suggest that a change in any type of sound feature elicits a change-related response that is inhibited by any type of preceding change stimulus, which reflects auto-inhibition of the change-responding circuit.

Effects of Sound-Pressure Change on the 40 Hz Auditory Steady-State Response and Change-Related Cerebral Response

The auditory steady-state response (ASSR) elicited by a periodic sound stimulus is a neural oscillation recorded by magnetoencephalography (MEG), which is phase-locked to the repeated sound stimuli. This ASSR phase alternates after an abrupt change in the feature of a periodic sound stimulus and returns to its steady-state value. An abrupt change also elicits a MEG component peaking at approximately 100-180 ms (called "Change-N1m"). We investigated whether both the ASSR phase deviation and Change-N1m were affected by the magnitude of change in sound pressure. The ASSR and Change-N1m to 40 Hz click-trains (1000 ms duration, 70 dB), with and without an abrupt change (± 5, ± 10, or ± 15 dB) were recorded in ten healthy subjects. We used the source strength waveforms obtained by a two-dipole model for measurement of the ASSR phase deviation and Change-N1m values (peak amplitude and latency). As the magnitude of change increased, Change-N1m increased in amplitude and decreased in latency. Similarly, ASSR phase deviation depended on the magnitude of sound-pressure change. Thus, we suspect that both Change-N1m and the ASSR phase deviation reflect the sensitivity of the brain's neural change-detection system.

Prepulse Inhibition of the Auditory Off-Response: A Magnetoencephalographic Study

A weak preceding sound stimulus attenuates the startle response evoked by an intense sound stimulus. Like startle reflexes, change-related auditory responses are suppressed by a weak leading stimulus (ie, a prepulse). We aim to examine whether a prepulse inhibits cerebral responses to the sound offset and how the prepulse magnitude affects the degree of the prepulse inhibition (PPI). Using magnetoencephalography, we recorded the Off-P50m elicited by an offset of a train sound of 100-Hz clicks in 12 healthy subjects. A single click slightly louder (+1.5, +3, or +5 dB) than the background sound of 80 dB was inserted 50 ms before the sound offset as a prepulse. We performed a dipole source analysis of the Off-P50m, and we measured its latency and amplitude using the source strength waveforms. The origin of the Off-P50m was estimated to be the auditory cortex on both hemispheres. The Off-P50m was clearly attenuated by the prepulses, and the degree of PPI was greater with a louder prepulse. The Off-P50m is considered to be a simple change-related response, which does not overlap with a processing of incoming sounds. Thus, the Off-P50m and its PPI comprise a valuable tool for investigating the neural inhibitory system.

GABAergic mechanisms involved in the prepulse inhibition of auditory evoked cortical responses in humans

Despite their essential roles in signal processing in the brain, the functions of interneurons currently remain unclear in humans. We recently developed a method using the prepulse inhibition of sensory evoked cortical responses for functional measurements of interneurons. When a sensory feature is abruptly changed in a continuous sensory stimulus, change-related cortical responses are recorded using MEG. By inserting a weak change stimulus (prepulse) before the test change stimulus, it is possible to observe the inhibition of the test response. By manipulating the prepulse–test interval (PTI), several peaks appear in inhibition, suggesting the existence of temporally distinct mechanisms. We herein attempted to separate these components through the oral administration of diazepam and baclofen. The test stimulus and prepulse were an abrupt increase in sound pressure in a continuous click train of 10 and 5 dB, respectively. The results obtained showed that the inhibition at PTIs of 10 and 20 ms was significantly greater with diazepam than with the placebo administration, suggesting increased GABA_A-mediated inhibition. Baclofen decreased inhibition at PTIs of 40 and 50 ms, which may have been due to the activation of GABA_B autoreceptors. Therefore, the present study separated at least two inhibitory mechanisms pharmacologically.

Inhibition in the Human Auditory Cortex

Despite their indispensable roles in sensory processing, little is known about inhibitory interneurons in humans. Inhibitory postsynaptic potentials cannot be recorded non-invasively, at least in a pure form, in humans. We herein sought to clarify whether prepulse inhibition (PPI) in the auditory cortex reflected inhibition via interneurons using magnetoencephalography. An abrupt increase in sound pressure by 10 dB in a continuous sound was used to evoke the test response, and PPI was observed by inserting a weak (5 dB increase for 1 ms) prepulse. The time course of the inhibition evaluated by prepulses presented at 10-800 ms before the test stimulus showed at least two temporally distinct inhibitions peaking at approximately 20-60 and 600 ms that presumably reflected IPSPs by fast spiking, parvalbumin-positive cells and somatostatin-positive, Martinotti cells, respectively. In another experiment, we confirmed that the degree of the inhibition depended on the strength of the prepulse, but not on the amplitude of the prepulse-evoked cortical response, indicating that the prepulse-evoked excitatory response and prepulse-evoked inhibition reflected activation in two different pathways. Although many diseases such as schizophrenia may involve deficits in the inhibitory system, we do not have appropriate methods to evaluate them; therefore, the easy and non-invasive method described herein may be clinically useful.

Gender-specific association between the COMT Val158Met polymorphism and openness to experience in panic disorder patients

BACKGROUND

Because major depression and panic disorder are both more prevalent among females and since several lines of evidence suggest that genetic factors might influence an individual's vulnerability to panic disorder, gene-gender interactions are being examined in such psychiatric disorders and mental traits. A number of studies have suggested that specific genes, e.g. catechol-O-methyltransferase (COMT), might lead to distinct clinical characteristics of panic disorder.

METHOD

We compared gender-specific personality-related psychological factors of 470 individuals with panic disorder and 458 healthy controls in terms of their COMT Val158Met polymorphism and their scores on the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) with a 1-way analysis of covariance.

RESULTS

In the male panic disorder patients, the NEO PI-R score for openness to experience was significantly lower in the Met/Met carrier group, whereas there was no such association among the female panic disorder patients or the male or female control groups.

CONCLUSION

The gender-specific effect of the COMT genotype suggests that the COMT Val/Met genotype may influence a personality trait, openness to experience, in males with panic disorder.

Gene×gene×gender interaction of BDNF and COMT genotypes associated with panic disorder

Genetic and gender differences are among the factors that have a role in the etiology of panic disorder (PD). It is thought that PD is related to neurotransmitter pathways, such as brain-derived neurotrophic factor (BDNF) and catechol-O-methyltransferase (COMT), both of which are involved in the regulation of the monoamine mechanism. We examined the interactions of BDNF, COMT and gender differences in terms of personality characteristics in PD. The subjects were 470 patients (178 men, 292 women) with a DSM-IV diagnosis of PD, and 458 healthy controls (195 men, 263 women). The subjects were further clinically characterized using the Revised NEO Personality Inventory (NEO-PI-R) and State-Trait Anxiety Inventory (STAI). COMT Val158Met polymorphisms (rs4680) and BDNF Val66Met (rs6265) polymorphisms were genotyped using allelic discrimination by a real-time PCR assay. A multivariate analysis of covariance (MANCOVA) was performed with STAI and NEO-PI-R scores as the dependent factor, gender and genotyping groups (BDNF and COMT) as fixed factors, and the covariate of age in the PD and healthy control groups. Post hoc MANCOVA tests were conducted to evaluate COMT × BDNF interactions. An interaction of BDNF × COMT × gender was confirmed in the PD group by MANCOVA on STAI scores and NEO-PI-R Neuroticism and Extraversion scores, whereas no association of such interactions was observed in the healthy controls. The anxiety sensitivity of the COMT Met+BDNF Val/Val carriers was higher than that of the COMT Val/Val+BDNF Val/Val carriers by post hoc MANCOVA. A significant BDNF × COMT × gender interaction was observed in the PD patients but not in the controls. Our findings partly demonstrated the involvement of a gene × gene × gender interaction in the pathogenesis of PD.

Prepulse inhibition of change-related P50m no correlation with P50m gating

Both prepulse inhibition (PPI) of the startle response and P50 sensory gating are important tools to investigate the inhibitory mechanisms of sensory processing. However, previous studies found no or a weak association between these two measures, which may have been due to the different indexes used. We examined the relationship between P50 sensory gating and P50 PPI. P50m sensory gating and PPI of Change-related P50m were assessed in 14 subjects using magnetoencephalography. Concerning P50m sensory gating, the amplitudes of the response to the second click relative to that to the first one were reduced by 43 and 47% for the left and right hemisphere, respectively. Change-related P50m was evoked by an abrupt sound pressure increase by 10 dB in a continuous click train of 70 dB. When this test stimulus was preceded by a click (prepulse) with a weaker sound pressure increase (5 dB) at a prepulse-test interval of 30, 60, or 90 ms, Change-P50m was suppressed by 33 ~ 65% while the prepulse itself elicited no or very weak P50m responses. Although the amplitude of the P50m response to the first click and the amplitude of the Change-P50m test alone response were positively correlated (r = 0.6), the degree of the inhibition of the two measures was not (r = -0.06 ~ 0.14). The neural origin was estimated to be located in the supratemporal plane around the superior temporal gyrus or Heschl’s gyrus and did not differ between P50m and Change-P50m. The present results suggest that P50m and Change-P50m are generated by a similar group of neurons in the auditory cortex, while the mechanisms of P50m sensory gating and Change-P50m PPI are different.

Differential mechanisms underlie the regulation of serotonergic transmission in the dorsal and median raphe nuclei by mirtazapine: a dual probe microdialysis study

RATIONALE

Blockade of α2 adrenoceptors and histamine H1 receptors plays important roles in the antidepressant and hypnotic effects of mirtazapine.

OBJECTIVES

However, it remains unclear how mirtazapine's actions at these receptors interact to affect serotonergic transmission in the dorsal (DRN) and median (MRN) raphe nuclei.

METHOD

Using dual-probe microdialysis, we determined the roles of α2 and H1 receptors in the effects of mirtazapine on serotonergic transmission in the DRN and MRN and their respective projection regions, the frontal (FC) and entorhinal (EC) cortices.

RESULTS

Mirtazapine (<30 μM) failed to alter extracellular serotonin levels when perfused alone into the raphe nuclei, but when co-perfused with a 5-HT1A receptor antagonist, mirtazapine increased serotonin levels in the DRN, MRN, FC, and EC. Serotonin levels in the DRN and FC were decreased by blockade and increased by activation of H1 receptors in the DRN. Serotonin levels in the MRN and EC were not affected by H1 agonists/antagonists perfused in the MRN. The increase in serotonin levels in the DRN and FC induced by DRN H1 receptor activation was attenuated by co-perfusion with mirtazapine. Furthermore, the increase in serotonin levels (DRN/FC) induced by DRN α2 adrenoceptor blockade was attenuated by concurrent DRN H1 blockade, whereas the increase in serotonin levels (MRN/EC) induced by MRN α2 adrenoceptor inhibition was unaffected by concurrent MRN H1 receptor blockade.

CONCLUSION

These results suggest that enhanced serotonergic transmission resulting from α2 adrenoceptor blockade is offset by subsequent activation of 5-HT1A receptors and, in the DRN but not MRN, H1 receptor inhibition. These pharmacological actions of mirtazapine may explain its antidepressant and hypnotic actions.

Source localization of posterior slow waves of youth using dipole modeling

AIM

Posterior slow waves of youth have a well-known electroencephalographic pattern that peaks in adolescence and usually disappears in adulthood. In general, posterior slow waves of youth are regarded as normal, but some reports have suggested that their presence is related to immature personalities or inappropriate social behavior. The physiological significance of this electroencephalographic pattern, however, remains unclear. The purpose of this study was to investigate the neural origins of posterior slow waves of youth using dipole source modeling.

METHODS

Electroencephalographic epochs, including clear posterior slow waves of youth, were visually selected from electroencephalograms obtained from six normal adolescents using 25 scalp electrodes. The selected epochs were then averaged by arranging the negative peak of the slow waves at the occipital area of each epoch on the time axis. The averaged waveforms consisting of six right and one left posterior slow waves of youth were used for dipole source analysis. A single equivalent current dipole was estimated for the averaged waveforms.

RESULTS

The best equivalent current dipoles were estimated to be located in or around the fusiform and middle occipital gyrus ipsilateral to the posterior slow waves of youth.

CONCLUSIONS

The location of the estimated dipoles of posterior slow waves of youth was on the so-called ventral visual pathway. Further research is required to clarify the physiological significance of posterior slow waves of youth with respect to their origin.

Prepulse inhibition of auditory change-related cortical responses

Background

Prepulse inhibition (PPI) of the startle response is an important tool to investigate the biology of schizophrenia. PPI is usually observed by use of a startle reflex such as blinking following an intense sound. A similar phenomenon has not been reported for cortical responses.

Results

In 12 healthy subjects, change-related cortical activity in response to an abrupt increase of sound pressure by 5 dB above the background of 65 dB SPL (test stimulus) was measured using magnetoencephalography. The test stimulus evoked a clear cortical response peaking at around 130 ms (Change-N1m). In Experiment 1, effects of the intensity of a prepulse (0.5 ~ 5 dB) on the test response were examined using a paired stimulation paradigm. In Experiment 2, effects of the interval between the prepulse and test stimulus were examined using interstimulus intervals (ISIs) of 50 ~ 350 ms. When the test stimulus was preceded by the prepulse, the Change-N1m was more strongly inhibited by a stronger prepulse (Experiment 1) and a shorter ISI prepulse (Experiment 2). In addition, the amplitude of the test Change-N1m correlated positively with both the amplitude of the prepulse-evoked response and the degree of inhibition, suggesting that subjects who are more sensitive to the auditory change are more strongly inhibited by the prepulse.

Conclusions

Since Change-N1m is easy to measure and control, it would be a valuable tool to investigate mechanisms of sensory gating or the biology of certain mental diseases such as schizophrenia.

Clozapine, but not haloperidol, enhances glial D-serine and L-glutamate release in rat frontal cortex and primary cultured astrocytes

BACKGROUND AND PURPOSE

Deficient transmission at the glutamate NMDA receptor is considered a key component of the pathophysiology of schizophrenia. However, the effects of antipsychotic drugs on the release of the endogenous NMDA receptor partial agonist, D-serine, remain to be clarified.

EXPERIMENTAL APPROACH

We determined the interaction between antipsychotic drugs (clozapine and haloperidol) and transmission-modulating toxins (tetanus toxin, fluorocitrate, tetrodotoxin) on the release of L-glutamate and D-serine in the medial prefrontal cortex (mPFC) of freely moving rats, using microdialysis, and primary cultures of astrocytes using extreme high-pressure liquid chromatography.

KEY RESULTS

Release of L-glutamate and D-serine in the mPFC and in cultured astrocytes was inhibited by tetanus toxin (a synaptobrevin inhibitor) and fluorocitrate (a glial toxin), whereas tetrodotoxin (a voltage-sensitive Na(+) blocker) inhibited depolarization-induced L-glutamate release in the mPFC without affecting that of D-serine. Clozapine (1 and 5 mg·kg(-1)), but not haloperidol (0.5 and 1 mg·kg(-1)), dose-dependently increased L-glutamate and D-serine release from both astrocytes and mPFC. Clozapine-induced release of L-glutamate and D-serine was also reduced by tetanus toxin and fluorocitrate. Tetrodotoxin reduced clozapine-induced mPFC L-glutamate release but not that of D-serine. Clozapine-induced L-glutamate release preceded clozapine-induced D-serine release. MK-801 (a NMDA receptor antagonist) inhibited the delayed clozapine-induced L-glutamate release without affecting that of D-serine.

CONCLUSIONS AND IMPLICATIONS

Clozapine predominantly activated glial exocytosis of D-serine, and this clozapine-induced D-serine release subsequently enhances neuronal L-glutamate release via NMDA receptor activation. The enhanced D-serine associated glial transmission seems a novel mechanism of action of clozapine but not haloperidol.

Electroencephalographic dipole source modeling of frontal intermittent rhythmic delta activity

BACKGROUND

Frontal intermittent rhythmic delta activity (FIRDA) on electroencephalography (EEG) consists of a run of rhythmic delta waves with frontal predominance. Although FIRDA is a relatively common abnormal EEG finding, the underlying mechanisms that produce FIRDA remain unclear. The aim of this study was to investigate the cortical source of FIRDA using dipole source modeling.

METHODS

We selected EEG epochs, including typical FIRDAs, from EEG recordings obtained using 25 scalp electrodes on 5 subjects. We averaged these epochs by arranging the negative peaks of the delta waves at the Fp electrodes and estimated dipoles for nine averaged waveforms.

RESULTS

Averaged waveforms were explained by a single-dipole model in seven FIRDAs and by a two-dipole model in the remaining two FIRDAs with high reliability. Estimated dipoles had a radial orientation with respect to the frontal pole and were located in the medial frontal region. The anterior cingulate cortex was the most common dipole location.

CONCLUSIONS

This is the first study to approach the fundamental FIRDA mechanism by dipole source modeling and to clarify that FIRDA may be generated from the medial frontal region, particularly from the anterior cingulate cortex.

Dopamine D2 and serotonin 5-HT1A receptors mediate the actions of aripiprazole in mesocortical and mesoaccumbens transmission

The antipsychotic agent aripiprazole acts as a partial agonist of dopamine D2 and serotonin 5-HT1A receptors. However, the detailed actions of aripiprazole in mesolimbic and mesocortical transmission remain to be clarified. To address this, we examined the effects of systemic and local administrations of aripiprazole on extracellular levels of dopamine and GABA in medial prefrontal cortex (mPFC), nucleus accumbens (NAc), and anterior (aVTA) and posterior (pVTA) ventral tegmental areas. Intraperitoneal injection of aripiprazole (0.5mg/kg) increased dopamine release in mPFC without affecting those in aVTA, pVTA, or NAc, whereas 10mg/kg decreased the release in all four regions. Local sulpiride administration in aVTA increased concentration-dependently dopamine release in both aVTA and NAc without affecting that in mPFC, whereas local aripiprazole administration in aVTA concentration-dependently decreased dopamine release in aVTA and mPFC without affecting that in NAc. Blockade of 5-HT1A receptor in aVTA produced aripiprazole-induced dopamine release in aVTA and prevented the aripiprazole-induced reduction of dopamine release in mPFC. Local administration of aripiprazole in mPFC increased dopamine and decreased GABA releases, whereas local administration of sulpiride had no effect on dopamine or GABA. In mPFC, blockade of 5-HT1A receptor prevented the aripiprazole-induced dopamine elevation and GABA reduction; however, under the activation of GABA(A) receptor, local perfusion with aripiprazole in mPFC decreased GABA release without affecting dopamine release. The results suggested that the combination of 5-HT1A and D2 partial agonistic actions of aripiprazole against mesocortical and mesoaccumbens transmission, explains, at least in part, the atypical antipsychotic properties of aripiprazole. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.