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Major depressive disorder (MDD) is associated with significant morbidity and mortality. Most antidepressant medications target the serotonin and norepinephrine transporters, but a significant minority of patients do not respond to treatment and novel therapeutic targets are needed. We previously identified a protein complex composed of the α7 nicotinic acetylcholine receptor (nAChR) and NMDA glutamate receptors (NMDARs), through which α7nAChR upregulates NMDAR function. Disruption of the α7nAChR–NMDAR complex with an interfering peptide blocked α7nAChR-mediated upregulation of NMDAR function and cue-induced reinstatement of nicotine seeking in rat models of relapse. Here we report that disrupting the α7nAChR–NMDAR complex with the interfering peptide also has antidepressant-like effects in the forced swim test (FST), a common rat behaviour screening test for antidepressant effects. Furthermore, the interfering peptide significantly increases extracellular signal-regulated kinase (ERK) activity in the animals subjected to the FST. Our results provide a novel potential therapeutic target for the development of new antidepressant medications. Supplementary Information The online version contains supplementary material available at 10.1186/s13041-021-00817-3.

Electroconvulsive therapy (ECT) is effective for major depressive disorder (MDD) but its effects on memory limit its widespread use. Magnetic seizure therapy (MST) is a potential alternative to ECT that may not adversely affect memory. In the current trial, consecutive patients with MDD consented to receive MST applied over the prefrontal cortex according to an open-label protocol. Depressive symptoms and cognition were assessed prior to, during and at the end of treatment. Patients were treated two to three times per week with high-frequency MST (i.e., 100 Hz) (N = 24), medium frequency MST (i.e., 60 or 50 Hz) (N = 26), or low-frequency MST (i.e., 25 Hz MST) (N = 36) using 100% stimulator output. One hundred and forty patients were screened; 86 patients with MDD received a minimum of eight treatments and were deemed to have an adequate course of MST; and 47 completed the trial per protocol, either achieving remission (i.e., 24-item Hamilton Rating Scale for Depression score 60% at two consecutive assessments; n = 17) or received a maximum of 24 sessions (n = 30). High-frequency (100 Hz) MST produced the highest remission rate (33.3%). Performance on most cognitive measures remained stable, with the exception of significantly worsened recall consistency of autobiographical information and significantly improved brief visuospatial memory task performance. Under open conditions, MST led to clinically meaningful reduction in depressive symptoms in patients with MDD and produced minimal cognitive impairment. Future studies should compare MST and ECT under double-blind randomized condition.

Schizophrenia is considered primarily as a cognitive disorder. However, functional outcomes in schizophrenia are limited by the lack of effective pharmacological and psychosocial interventions for cognitive impairment. GABA (gamma-aminobutyric acid) interneurons are the main inhibitory neurons in the central nervous system (CNS), and they play a critical role in a variety of pathophysiological processes including modulation of cortical and hippocampal neural circuitry and activity, cognitive function-related neural oscillations (eg, gamma oscillations) and information integration and processing. Dysfunctional GABA interneuron activity can disrupt the excitatory/inhibitory (E/I) balance in the cortex, which could represent a core pathophysiological mechanism underlying cognitive dysfunction in schizophrenia. Recent research suggests that selective modulation of the GABAergic system is a promising intervention for the treatment of schizophrenia-associated cognitive defects. In this review, we summarized evidence from postmortem and animal studies for abnormal GABAergic neurotransmission in schizophrenia, and how altered GABA interneurons could disrupt neuronal oscillations. Next, we systemically reviewed a variety of up-to-date subtype-selective agonists, antagonists, positive and negative allosteric modulators (including dual allosteric modulators) for α5/α3/α2 GABA(A) and GABA(B) receptors, and summarized their pro-cognitive effects in animal behavioral tests and clinical trials. Finally, we also discuss various representative histone deacetylases (HDAC) inhibitors that target GABA system through epigenetic modulations, GABA prodrug and presynaptic GABA transporter inhibitors. This review provides important information on current potential GABA-associated therapies and future insights for development of more effective treatments.

Epigenetic gene-regulation abnormalities have been implicated in various neuropsychiatric disorders including schizophrenia and depression, as well as in the regulation of mood and anxiety. In addition, epigenetic mechanisms are involved in the actions of psychiatric drugs. Current anxiolytic drugs have significant shortcomings, and development of new medications is warranted. Two proteins, G9a (also known as EHMT2 or KMT1C) and GLP (G9a-like protein, also known as EHMT1 or KMT1D), which methylate lysine 9 of histone H3 (H3K9), could be promising anxiolytic targets. Postnatal genetic knock-out of G9a reduces anxiety-related behavior, consistent with the reduction of G9a levels by some medications used to treat anxiety (amitriptyline, imipramine and paroxetine). Conversely, there is increased anxiety-like behavior in mice with GLP haplodeficiency. We sought to determine whether two pharmacological inhibitors of G9a/GLP, UNC0642 and A-366, would have similar effects to genetic G9a/GLP insufficiency. We found that G9a/GLP inhibition with either compound reduced anxiety-like behaviors when administered to adult mice, in conjunction with decreased H3K9 methylation in the brain. In contrast, exposure to these compounds from embryonic day 9.5 (E9.5) until birth increased anxiety-like behaviors and decreased social interaction in adulthood, while H3K9 methylation was at normal levels in the brains of the adult mice. These findings reinforce genetic evidence that G9a/GLP has different effects on anxiety-like behavior at different stages of brain development, and suggest that targeting this histone methyltransferase pathway could be useful for developing new anxiolytic drugs. These data also suggest that antidepressant exposure in utero could have negative effects in adulthood, and further investigation of these effects is warranted.

Following publication of the original article [1], the authors reported that one of the authors’ names is spelled incorrectly.

Depression, or major depressive disorder (MDD), is a serious mental illness that causes substantial worldwide disability. Current antidepressant medications mostly target the serotonin and norepinephrine neurotransmitter systems. These drugs are ineffective in many patients, and there are limited options for treatment-resistant depression. The dopamine neurotransmitter system has recently been identified as another modulator of mood and depressive symptoms, and a recently discovered interaction between the dopamine D1 and D2 receptor may be a novel antidepressant target.

Tardive dyskinesia (TD) has a pharmacogenetic component in which the interaction of antipsychotic exposure with individual genetic variation mediates risk. The glial cell line-derived neurotrophic factor (GDNF) signalling pathway has been associated with neuroprotective effects in central dopaminergic neurons and spinal motor neurons. Clinical trials have also investigated whether GDNF may ameliorate Parkinson's disease symptoms.We tested whether variants in the GDNF receptor alpha 2 (GFRA2) gene could play a role in TD susceptibility evaluating 16 variants in 172 Caucasian schizophrenia subjects.We observed one significant allelic association (rs4739285, permuted p = 0.042) and two genotypic associations: rs4739285 under additive inheritance model and rs4739217 under dominant inheritance model (permuted p = 0.044). Moreover, carriers of the major alleles for both rs6587002 and rs4739217 presented significantly higher risk for TD (OR = 2.04, permuted p = 0.014), while subjects with the minor allele for rs4739217 and the major allele for rs6988470 were less likely to have TD (OR = 0.21, permuted p = 0.0007).Haplotype results indicate that the minor allele of the rs4739217 is a risk factor for TD (permuted allelic p = 0.074). Age was also a risk factor for TD in our sample (p = 0.0001). Taken together, our findings suggest that GFRA2 genetic variants and age may play a role in TD susceptibility, but further work is required to confirm these findings.

Twin studies have provided the basis for genetic and epidemiological studies in human complex traits. As epigenetic factors can contribute to phenotypic outcomes, we conducted a DNA methylation analysis in white blood cells (WBC), buccal epithelial cells and gut biopsies of 114 monozygotic (MZ) twins as well as WBC and buccal epithelial cells of 80 dizygotic (DZ) twins using 12K CpG island microarrays. Here we provide the first annotation of epigenetic metastability of approximately 6,000 unique genomic regions in MZ twins. An intraclass correlation (ICC)-based comparison of matched MZ and DZ twins showed significantly higher epigenetic difference in buccal cells of DZ co-twins (P = 1.2 x 10(-294)). Although such higher epigenetic discordance in DZ twins can result from DNA sequence differences, our in silico SNP analyses and animal studies favor the hypothesis that it is due to epigenomic differences in the zygotes, suggesting that molecular mechanisms of heritability may not be limited to DNA sequence differences.

A number of human and animal studies implicate GSK3 in the pathophysiology and genetics of schizophrenia. In general, the data suggest that phosphorylation levels of GSK3beta are reduced in schizophrenia, resulting in increased GSK3beta activity. Since GSK3beta regulation is altered in schizophrenia, polymorphic variation in this gene may affect susceptibility to schizophrenia or treatment response.To analyze GSK3beta genetic variants for association with schizophrenia and clozapine response.We examined GSK3beta markers in 185 matched case-control subjects, 85 small nuclear families, and 150 schizophrenia patients treated with clozapine for 6 months.Three markers (rs7624540, rs4072520, and rs6779828) showed genotypic association with schizophrenia in the case-control sample. We did not observe any family and clozapine response association with a specific allele, genotype, or haplotype.Our results suggest that GSK3beta polymorphisms might be involved in schizophrenia risk but do not appear to play a significant role in clozapine response.

A number of linkage studies have previously implicated the region of chromosome 13q34 in schizophrenia. Chumakov and colleagues (2002) identified a gene complex called G72 (now termed D-amino acid oxidase activator: DAOA)/G30 in this region and performed association analyses of the DAOA/G30 as well as the D-amino-acid oxidase (DAAO) gene with schizophrenia. DAAO oxidizes D-serine, a potent activator of the N-methyl-D-aspartate (NMDA) type glutamate receptor in the human brain whereas the DAOA protein is considered an activator of DAAO. The interaction of these two genes has thus been implicated in the NMDA receptor regulation pathway in schizophrenia. To date, several studies have shown a relatively consistent positive association between schizophrenia and DAOA/G30, but not with DAAO. The aim of our study was to further evaluate the contributions of these genes to the susceptibility to schizophrenia using two different sample sets. Our sample consisted of 168 matched case-control pairs as well as a family-based sample (n=113) for transmission disequilibrium test. Significant associations between the DAOA/G30 M-7 and M-18 polymorphisms and schizophrenia were observed in our case-control sample whereas no associations were observed for DAAO markers. We also observed significant or suggestive transmission disequilibrium for DAOA/G30 M-7, M-23, and M-24 to probands with schizophrenia in our family-based sample. Subsequent analysis of haplotypes made up of four DAOA/G30 markers, one marker selected from each of two linkage disequilibrium blocks that were observed in our sample as well as both ends (M-7 and M-25), were also associated with schizophrenia. Our data provide further evidence that the DAOA/G30 locus may play a role in the pathophysiology of schizophrenia. Although no direct link to genetic polymorphism in these genes and NMDA receptor function has been revealed, the present findings support previous reports implicating DAOA/G30 as susceptibility genes for schizophrenia. Further research is warranted to determine the functional variation underlying these findings and to relate this to the pathophysiology of schizophrenia.

This study presents a framework for numerical simulations based upon micromechanical parameters in modeling progressive failures of heterogeneous rock specimens under compression. In our numerical simulations, a Weibull distribution of the strength and elastic properties of the finite elements is assumed, and the associated Weibull parameters are estimated in terms of microstructural properties, such as crack size distribution and grain size, through microscopic observations of microcracks. The main uncertainty in this procedure lies on the fact that various ways can be used to formulate a “microcrack size distribution” in relating to the Weibull parameters. As one possible choice, the present study uses the number of counted cracks per unit scanned volume per grain size to formulate the crack distributions. Finally, as a tool, the Rock Failure Process Analysis code (RFPA2D) is adopted for simulating the progressive failure and microseismicity of heterogeneous rocks by using an elastic-damage finite-element approach. To verify our framework, compression tests on marble specimens are conducted, and the measured acoustic emissions (AE) are compared with those predicted by the numerical simulations. The mode of failure, compressive strength and AE pattern of our simulations basically agree with experimental observations.

Although the genetic contribution to schizophrenia is substantial, positive findings in whole-genome linkage scans have not been consistently replicated. We analyzed gene expression in various rat conditions to identify novel candidate genes for schizophrenia. Suppression subtraction hybridization (SSH), with polyA mRNA from temporal and frontal cortex of rats, was used to identify differentially expressed genes. Expression of mRNA was compared between adult Lewis and Fischer 344 (F344) rats, adult and postnatal day 6 (d6) F344, and adult F344 treated with haloperidol or control vehicle. These groups were chosen because each highlights a particular aspect of schizophrenia: differences in strain vulnerability to behavioral analogs of psychosis; factors that may relate to disease onset in relation to CNS development; and improvement of symptoms by haloperidol. The 14-3-3 gene family, as represented by 14-3-3gamma and 14-3-3zeta isoforms in the SSH study, and SNAP-25 were among the candidate genes. Genetic association between schizophrenia and the 14-3-3eta gene, positioned close to a genomic locus implicated in schizophrenia, and SNAP-25 genes was analyzed in 168 schizophrenia probands and their families. These findings address three different genes in the 14-3-3 family. We find a significant association with schizophrenia for two polymorphisms in the 14-3-3eta gene: a 7 bp variable number of tandem repeats in the 5' noncoding region (P=0.036, 1 df), and a 3' untranslated region SNP (753G/A) that is an RFLP visualized with Ava II (P=0.028). There was no significant genetic association with SNAP-25. The candidate genes identified may be of functional importance in the etiology, pathophysiology or treatment response of schizophrenia or psychotic symptoms. This is to our knowledge the first report of a significant association between the 14-3-3eta-chain gene and schizophrenia in a family-based sample, strengthening prior association reports in case-control studies and microarray gene expression studies.

Background There is evidence for neurodevelopmental aberrations in both schizophrenia and bipolar disorder. We have studied the genes for synaptosomal associated protein of 25 kilodaltons (SNAP-25) and the brain derived neurotrophic factor (BDNF), that are known to be involved in normal brain development. SNAP-25 expression is associated with regions of high synaptic plasticity and is required for axonal elongation. A strain of mouse designated coloboma possessing a 2 cM deletion encompassing the Snap25 gene exhibits hyperactivity, delayed development, and abnormalities in dopaminergic, serotonergic, and glutamatergic transmission. Additionally, several studies have suggested a direct involvement of SNAP-25 in schizophrenia etiology based upon altered levels of brain and CSF expression. Furthermore, our group (Wong et al., 2003) have observed SNAP-25 expression to be significantly altered in rats treated with the antipsychotic medication haloperidol, versus controls. We examined transmission of alleles at three single nucleotide polymorphisms in the SNAP-25 gene in more than 100 schizophrenia triad families and found evidence of a haplotype related to the disease (Klempan et al., 2002).