Mild stress accumulation limits GABAergic synaptic plasticity in the lateral habenula

Nighttime-specific differential gene expression in suprachiasmatic nucleus and habenula is associated with resilience to chronic social stress

The molecular mechanisms that link stress and biological rhythms still remain unclear. The habenula (Hb) is a key brain region involved in regulating diverse types of emotion-related behaviours while the suprachiasmatic nucleus (SCN) is the body's central clock. To investigate the effects of chronic social stress on transcription patterns, we performed gene expression analysis in the Hb and SCN of stress-naïve and stress-exposed mice. Our analysis revealed a large number of differentially expressed genes and enrichment of synaptic and cell signalling pathways between resilient and stress-naïve mice at zeitgeber 16 (ZT16) in both the Hb and SCN. This transcriptomic signature was nighttime-specific and observed only in stress-resilient mice. In contrast, there were relatively few differences between the stress-susceptible and stress-naïve groups across time points. Our results reinforce the functional link between circadian gene expression patterns and differential responses to stress, thereby highlighting the importance of temporal expression patterns in homoeostatic stress responses.

GABAB1 receptor knockdown in prefrontal cortex induces behavioral aberrations associated with autism spectrum disorder in mice

Autism spectrum disorder (ASD) is a set of heterogeneous neurodevelopmental disorders, characterized by social interaction deficit, stereotyped or repetitive behaviors. Apart from these core symptoms, a great number of individuals with ASD exhibit higher levels of anxiety and memory deficits. Previous studies demonstrate pronounced decrease of γ-aminobutyric acid B1 receptor (GABAB1R) protein level of frontal lobe in both ASD patients and animal models. The aim of the present study was to determine the role of GABAB1R in ASD-related behavioral aberrations. Herein, the protein and mRNA levels of GABAB1R in the prefrontal cortex (PFC) of sodium valproic acid (VPA)-induced mouse ASD model were determined by Western blot and qRT-PCR analysis, respectively. Moreover, the behavioral abnormalities in naive mice with GABAB1R knockdown mediated by recombinant adeno-associated virus (rAAV) were assessed in a comprehensive test battery consisted of social interaction, marble burying, self-grooming, open-field, Y-maze and novel object recognition tests. Furthermore, the action potential changes induced by GABAB1R deficiency were examined in neurons within the PFC of mouse. The results show that the mRNA and protein levels of GABAB1R in the PFC of prenatal VPA-induced mouse ASD model were decreased. Concomitantly, naive mice with GABAB1R knockdown exhibited ASD-like behaviors, such as impaired social interaction and communication, elevated stereotypes, anxiety and memory deficits. Patch-clamp recordings also revealed that GABAB1R knockdown provoked enhanced neuronal excitability by increasing action potential discharge frequencies. Overall, these findings support a notion that GABAB1R deficiency might contribute to ASD-like phenotypes, with the pathogenesis most likely resulting from enhanced neuronal excitability. SUBHEADINGS: GABAB1 Knockdown Induces Behavioral Aberrations with ASD.

Behavioral and neuro-functional consequences of eliminating the KCNQ3 GABA binding site in mice

Voltage-gated potassium (Kv) channels formed by α subunits KCNQ2-5 are important in regulating neuronal excitability. We previously found that GABA directly binds to and activates channels containing KCNQ3, challenging the traditional understanding of inhibitory neurotransmission. To investigate the functional significance and behavioral role of this direct interaction, mice with a mutated KCNQ3 GABA binding site (Kcnq3-W266L) were generated and subjected to behavioral studies. Kcnq3-W266L mice exhibited distinctive behavioral phenotypes, of which reduced nociceptive and stress responses were profound and sex-specific. In female Kcnq3-W266L mice, the phenotype was shifted towards more nociceptive effects, while in male Kcnq3-W266L mice, it was shifted towards the stress response. In addition, female Kcnq3-W266L mice exhibited lower motor activity and reduced working spatial memory. The neuronal activity in the lateral habenula and visual cortex was altered in the female Kcnq3-W266L mice, suggesting that GABAergic activation of KCNQ3 in these regions may play a role in the regulation of the responses. Given the known overlap between the nociceptive and stress brain circuits, our data provide new insights into a sex-dependent role of KCNQ3 in regulating neural circuits involved in nociception and stress, via its GABA binding site. These findings identify new targets for effective treatments for neurological and psychiatric conditions such as pain and anxiety.

Circuits regulating pleasure and happiness - focus on potential biomarkers for circuitry including the habenuloid complex

INTRODUCTION

The multiplicity and complexity of the neuronal connections in the central nervous system make it difficult to disentangle circuits that play an essential role in the development or treatment of (neuro)psychiatric disorders. By choosing the evolutionary development of the forebrain as a starting point, a certain order in the connections can be created. The dorsal diencephalic connection (DDC) system can be applied for the development of biomarkers that can predict treatment response.

MATERIALS AND METHODS

After providing a brief introduction to the theory, we examined neuroanatomical publications on the connectivity of the DDC system. We then searched for neurochemical components that are specific for the habenula.

RESULTS AND DISCUSSION

The best strategy to find biomarkers that reflect the function of the habenular connection is to use genetic variants of receptors, transporters or enzymes specific to this complex. By activating these with probes and measuring the response in people with different functional genotypes, the usefulness of biomarkers can be assessed.

CONCLUSIONS

The most promising biomarkers in this respect are those linked to activation or inhibition of the nicotine receptor, dopamine D4 receptor, μ-opioid receptor and also those of the functioning of habenular glia cells (astrocytes and microglia).

Multi-level variations of lateral habenula in depression: A comprehensive review of current evidence

Despite extensive research in recent decades, knowledge of the pathophysiology of depression in neural circuits remains limited. Recently, the lateral habenula (LHb) has been extensively reported to undergo a series of adaptive changes at multiple levels during the depression state. As a crucial relay in brain networks associated with emotion regulation, LHb receives excitatory or inhibitory projections from upstream brain regions related to stress and cognition and interacts with brain regions involved in emotion regulation. A series of pathological alterations induced by aberrant inputs cause abnormal function of the LHb, resulting in dysregulation of mood and motivation, which present with depressive-like phenotypes in rodents. Herein, we systematically combed advances from rodents, summarized changes in the LHb and related neural circuits in depression, and attempted to analyze the intrinsic logical relationship among these pathological alterations. We expect that this summary will greatly enhance our understanding of the pathological processes of depression. This is advantageous for fostering the understanding and screening of potential antidepressant targets against LHb.