A Prelimbic Cortex-Thalamus Circuit Bidirectionally Regulates Innate and Stress-induced Anxiety-like Behavior.

Anxiety-related disorders respond to cognitive behavioral therapies, which involved the medial prefrontal cortex (mPFC). Previous studies have suggested that subregions of the mPFC have different and even opposite roles in regulating innate anxiety. However, the specific causal targets of their descending projections in modulating innate anxiety and stress-induced anxiety have yet to be fully elucidated. Here, we found that among the various downstream pathways of the prelimbic cortex (PL), a subregion of the mPFC, PL-mediodorsal thalamic nucleus (MD) projection and PL-ventral tegmental area (VTA) projection exhibited antagonistic effects on anxiety-like behavior, while the PL-MD projection but not PL-VTA projection was necessary for the animal to guide anxiety-related behavior. In addition, MD-projecting PL neurons bidirectionally regulated remote but not recent fear memory retrieval. Notably, restraint stress induced high-anxiety state accompanied by strengthening the excitatory inputs onto MD-projecting PL neurons, and inhibiting PL-MD pathway rescued the stress-induced anxiety. Our findings reveal that the activity of PL-MD pathway may be an essential factor to maintain certain level of anxiety, and stress increased the excitability of this pathway, leading to inappropriate emotional expression, and suggest that targeting specific PL circuits may aid the development of therapies for the treatment of stress-related disorders.Significance statement This study provides insight into PL downstream pathways for regulating innate and stress-induced anxiety-like behavior. We reported that PL-mediodorsal thalamic nucleus (MD) projection and PL-ventral tegmental area (VTA) projection exhibited antagonistic effects on anxiety-like behavior, while the PL-MD projection but not PL-VTA projection was necessary for the animal to guide anxiety-related behavior. In addition, this study provides definite evidence that MD-projecting PL neurons bidirectionally regulated remote fear memory retrieval and concordant with a role for the PL-MD in anxiety. Moreover, this study is the first demonstration that restraint stress induced high-anxiety state accompanied by strengthening the excitatory inputs onto MD-projecting PL neurons, and inhibiting PL-MD pathway rescued the stress-induced anxiety.

PV network plasticity mediated by neuregulin1-ErbB4 signalling controls fear extinction.

Neuroplasticity in the medial prefrontal cortex (mPFC) is essential for fear extinction, the process of which forms the basis of the general therapeutic process used to treat human fear disorders. However, the underlying molecules and local circuit elements controlling neuronal activity and concomitant induction of plasticity remain unclear. Here we show that sustained plasticity of the parvalbumin (PV) neuronal network in the infralimbic (IL) mPFC is required for fear extinction in adult male mice and identify the involvement of neuregulin 1-ErbB4 signalling in PV network plasticity-mediated fear extinction. Moreover, regulation of fear extinction by basal medial amygdala (BMA)-projecting IL neurons is dependent on PV network configuration. Together, these results uncover the local molecular circuit mechanisms underlying mPFC-mediated top-down control of fear extinction, suggesting alterative therapeutic approaches to treat fear disorders.

[Effects of GPR81 agonist on insulin resistance in rats with nonalcoholic fatty liver disease].

Objective: To investigate the effects of NOD-like receptor protein 3 (NLRP3) signaling pathway on insulin resistance and the intervention of lactic acid receptor G protein-coupled receptor 81 (GPR81) agonist in nonalcoholic fatty liver disease (NAFLD) rats. Methods: Thirty SD male rats were randomly divided into three groups: control group, NAFLD group and GPR81 agonist group, with 10 rats in each group. Nonalcoholic fatty liver rat model was established by high fat diet. The rats in GPR81 agonist group were injected intraperitoneally with GPR81 specific agonist lactate (50 nmol/L) on the basis of nonalcoholic fatty liver model once a week, and the other two groups were injected with the same amount of normal saline for 12 weeks. The levels of liver biochemical indexes, fasting blood glucose, insulin and inflammatory factors in liver homogenate were measured, and the histopathological morphology of liver in each group was observed. The protein expressions of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), cysteinyl aspartate specific proteinase-1 (caspase-1), insulin receptor substrate 1 (IRS-1), Tyr465-IRS-1, Ser636-IRS-1, glucose transporter 4 (GLUT4) in liver tissue were detected by Western blot. The mRNA expression levels of NLRP3, ASC, caspase-1, IRS-1 and GLUT4 in liver tissue were detected by qRT-PCR. Results: Compared with the control group, the serum levels of triglyceride (TG), alanine aminotransfease (ALT), aspartate aminotransfease (AST), fasting plasma glucose (FPG), fasting insulin (FINS) and homeostasis model assessment of insulin resistance (HOMA-IR) of NAFLD group were increased significantly (P＜ 0.05). The results of liver histopathology showed that in NAFLD group, there were obvious fatty changes in liver tissue, fat droplets in hepatocytes and inflammatory cell infiltration. And the mRNA and protein expressions of NLRP3, ASC, caspase-1 and the protein expression of Ser636-IRS-1 in NAFLD group were increased significantly, and the contents of interleukin 1ß (IL-1ß) and interleukin 18 (IL-18) in liver and serum were increased, while the mRNA and protein expressions of IRS-1 and GLUT4 and Tyr465-IRS-1 were decreased significantly (P＜0.05). Compared with NAFLD group, the above indexes of GPR81 agonist group were all significantly improved. Conclusion: The activation of NLRP3 signaling pathway mediates the production of inflammatory factors and promotes the development of NAFLD. GPR81 agonist may be a potential treatment for NAFLD.

Distinct projections from the infralimbic cortex exert opposing effects in modulating anxiety and fear.

Anxiety-related disorders can be treated by cognitive therapies and transcranial magnetic stimulation, which involve the medial prefrontal cortex (mPFC). Subregions of the mPFC have been implicated in mediating different and even opposite roles in anxiety-related behaviors. However, precise causal targets of these top-down connections among diverse possibilities have not been established. Here, we show that the lateral septum (LS) and the central nucleus of the amygdala (CeA) represent 2 direct targets of the infralimbic cortex (IL), a subregion of the mPFC that modulates anxiety and fear. Two projections were unexpectedly found to exert opposite effects on the anxious state and learned freezing: the IL-LS projection promoted anxiety-related behaviors and fear-related freezing, whereas the IL-CeA projection exerted anxiolytic and fear-releasing effects for the same features. Furthermore, selective inhibition of corresponding circuit elements showed opposing behavioral effects compared with excitation. Notably, the IL-CeA projection implemented top-down control of the stress-induced high-anxiety state. These results suggest that distinct IL outputs exert opposite effects in modulating anxiety and fear and that modulating the excitability of these projections with distinct strategies may be beneficial for the treatment of anxiety disorders.

ErbB4 knockdown in serotonergic neurons in the dorsal raphe induces anxiety-like behaviors.

There is a close relationship between serotonergic (5-HT) activity and anxiety. ErbB4, a receptor tyrosine kinase, is expressed in 5-HT neurons. However, whether ErbB4 regulates 5-HT neuronal function and anxiety-related behaviors is unclear. Here, using transgenic and viral approaches, we show that mice with ErbB4 deficiency in 5-HT neurons exhibit heightened anxiety-like behavior and impaired fear extinction, possibly due to an increased excitability of 5-HT neurons in the dorsal raphe nucleus (DRN). Notably, the chemogenetic inhibition of 5-HT neurons in the DRN of ErbB4 mutant mice rescues anxiety-like behaviors. Altogether, our results unravel a previously unknown role of ErbB4 signaling in the regulation of DRN 5-HT neuronal function and anxiety-like behaviors, providing novel insights into the treatment of anxiety disorders.

Erbin in Amygdala Parvalbumin-Positive Neurons Modulates Anxiety-like Behaviors.

BACKGROUND: Anxiety disorders are the most common psychiatric diseases, affecting 28% of people worldwide within their lifetime. The excitation-inhibition imbalance in the amygdala is thought to be an underlying pathological mechanism; however, the cellular and molecular control of amygdala excitation-inhibition balance is largely unknown. METHODS: By using mice expressing chemogenetic activator or inhibitor channel in amygdala parvalbumin (PV) neurons, Erbin mutant mice, and mice with Erbin specifically knocked down in amygdala PV neurons, we systematically investigated the role of amygdala PV neurons and Erbin expressed therein in the pathogenesis of anxiety disorders using the combined approaches of immunohistochemistry, electrophysiology, and behavior. RESULTS: In naïve mice, chemogenetic inhibition of PV neurons produced anxiogenic effects, suggesting an essential role in the regulation of anxiety. In stressed mice with anxiety, excitatory postsynaptic responses on amygdala PV neurons were selectively diminished, accompanied by a decreased expression of Erbin specifically in amygdala PV neurons. Remarkably, both Erbin mutant mice and amygdala PV-specific Erbin knockdown mice exhibited impaired excitatory postsynaptic responses on amygdala PV neurons and increased anxiety-like behaviors. Furthermore, chemogenetic activation of amygdala PV neurons normalized anxiety behaviors in amygdala PV-specific Erbin knockdown mice and stressed mice. CONCLUSIONS: Together, these results demonstrate that Erbin in PV neurons is critical for maintaining the excitation-inhibition balance in the amygdala and reveal a novel pathophysiological mechanism for anxiety disorders.

Satb2 Ablation Impairs Hippocampus-Based Long-Term Spatial Memory and Short-Term Working Memory and Immediate Early Genes (IEGs)-Mediated Hippocampal Synaptic Plasticity.

Special AT-rich sequence-binding protein 2 (Satb2) is a protein binding to the matrix attachment regions of DNA and important for gene regulation. Patients with SATB2 mutation usually suffer moderate to severe mental retardation. However, the mechanisms for the defects of intellectual activities in patients with SATB2 mutation are largely unclear. Here we established the heterozygous Satb2 mutant mice and Satb2 conditional knockout mice to mimic the patients with SATB2 mutation and figured out the role of Satb2 in mental activities. We found that the spatial memory and working memory were significantly damaged in the heterozygous Satb2 mutant mice, early postnatal Satb2-deficient mice (CaMKIIα-Cre+Satb2fl/fl mice), and adult Satb2 ablation mice (Satb2fl/fl mice injected with CaMKIIα-Cre virus). Functionally, late phase long-term potentiation (L-LTP) in these Satb2 mutant mice was greatly impaired. Morphologically, in CA1 neurons of CaMKIIα-Cre+Satb2fl/fl mice, we found decreased spine density of the basal dendrites and less branches of apical dendrites that extended into lacunar molecular layer. Mechanistically, expression levels of immediate early genes (IEGs) including Fos, FosB, and Egr1 were significantly decreased after Satb2 deletion. And, Satb2 could regulate expression of FosB by binding to the promoter of FosB directly. In general, our study uncovers that Satb2 plays an important role in spatial memory and working memory by regulating IEGs-mediated hippocampal synaptic plasticity.