The claustrum-prelimbic cortex circuit through dynorphin/κ-opioid receptor signaling underlies depression-like behaviors associated with social stress etiology.

Ample evidence has suggested the stress etiology of depression, but the underlying mechanism is not fully understood yet. Here, we report that chronic social defeat stress (CSDS) attenuates the excitatory output of the claustrum (CLA) to the prelimbic cortex (PL) through the dynorphin/κ-opioid receptor (KOR) signaling, being critical for depression-related behaviors in male mice. The CSDS preferentially impairs the excitatory output from the CLA onto the parvalbumin (PV) of the PL, leading to PL micronetwork dysfunction by disinhibiting pyramidal neurons (PNs). Optogenetic activation or inhibition of this circuit suppresses or promotes depressive-like behaviors, which is reversed by chemogenetic inhibition or activation of the PV neurons. Notably, manipulating the dynorphin/KOR signaling in the CLA-PL projecting terminals controls depressive-like behaviors that is suppressed or promoted by optogenetic activation or inhibition of CLA-PL circuit. Thus, this study reveals both mechanism of the stress etiology of depression and possibly therapeutic interventions by targeting CLA-PL circuit.

A morphine reward generalization mouse model based on conditioned place preference and aversion.

BACKGROUND: Conditioned place preference (CPP) is a common behavioral paradigm for studying the association of unconditioned stimulus reward memory with context. Generalization is a flexible memory recall pattern developed on the basis of original memory. Drug-seeking behaviors in substance use disorders (SUDs) exhibit diversity, which we generally attribute to the highly generalized features of SUD memory. However, to date, there are no animal models for SUD generalization studies. METHODS: We design the generalization box (G-box) and the generalization retrieval process based on the conditioned place preference (CPP) model. In the memory retrieval stage, we replaced the conditioning CPP box (T-box) with a generalization box (G-box) to study drug generalization memory. For appearance, the generalized boxes have different angles and numbers of sides compared to the conditioning boxes. For the visual cues, the shapes of the symbols are different (triangle icons for the hexagonal chamber and dot icons for the round chamber), but the orientation information remains the same. To establish CPP generalization, the mice received morphine on the vertical or horizontal side of a conditioning box (T-box) and saline on the other side. Then, after CPP conditioning, the generalization test was performed in a generalization box (G-box: hexagonal chamber and Gr-box: round chamber) 21 days later. RESULTS: CPP-conditioned mice still displayed a clear preference for similar visual information in the G-box. CPA-conditioned mice behaved similarly to CPP, with mice consistently avoiding similar visual information in the G-box. We further observed that the generalization results are similar using two generalization boxes (G-box and Gr-box). CONCLUSION: In this study, we succeeded in creating a simple and effective generalization model for morphine reward. The establishment of this model provides a new tool for generalization studies of SUD and therapy in humans.

High Morphine Use Disorder Susceptibility Is Predicted by Impaired Learning Ability in Mice.

An obvious reason for substance uses disorders (SUDs) is drug craving and seeking behavior induced by conditioned context, which is an abnormal solid context memory. The relationship between susceptibility to SUD and learning ability remains unclear in humans and animal models. In this study, we found that susceptibility to morphine use disorder (MUD) was negatively correlated with learning ability in conditioned place preference (CPP) in C57 mice. By using behavioral tests, we identified the FVB mouse as learning impaired. In addition, we discovered that learning-relevant proteins, such as the glutamate receptor subunits GluA1, NR1, and NR2A, were decreased in FVB mice. Finally, we assessed the context learning ability of FVB mice using the CPP test and priming. We found that FVB mice had lower learning performance with respect to normal memory but higher performance of morphine-reinstatement memory. Compared to C57 mice, FVB mice are highly sensitive to MUDs. Our results suggest that SUD susceptibility is predicted by impaired learning ability in mice; therefore, learning ability can play a simple and practical role in identifying high-risk SUD groups.

Early memory impairment is accompanied by changes in GluA1/p-GluA1 in APP/PS1 mice.

AIMS: Exploring the neurobiological mechanisms of early AD damage Background: The early diagnosis of Alzheimer's disease (AD) has a very important impact on the prognosis of AD. However, the early symptoms of AD are not obvious and difficult to diagnose. Existing studies have rarely explored the mechanism of early AD. AMPARs are early important learning memory-related receptors. However, it is not clear how the expression levels of AMPARs change in early AD. OBJECTIVE: We explored learning memory abilities and AMPAR expression changes in APP/PS1 mice at 4 months, 8 months, and 12 months. METHOD: We used the classic Morris water maze to explore the learning and memory impairment of APP/PS1 mice and used western blotting to explore the changes in AMPARs in APP/PS1 mice. RESULT: We found that memory impairment occurred in APP/PS1 mice as early as 4 months of age, and the impairment of learning and memory gradually became serious with age. The changes in GluA1 and p-GluA1 were most pronounced in the early stages of AD in APP/PS1 mice. CONCLUSION: Our study found that memory impairment in APP/PS1 mice could be detected as early as 4 months of age, and this early injury may be related to GluA1.

Retrosplenial Cortex Effects Contextual Fear Formation Relying on Dysgranular Constituent in Rats.

Animal contextual fear conditioning (CFC) models are the most-studied forms used to explore the neural substances of posttraumatic stress disorder (PTSD). In addition to the well-recognized hippocampal-amygdalar system, the retrosplenial cortex (RSC) is getting more and more attention due to substantial involvement in CFC, but with a poor understanding of the specific roles of its two major constituents-dysgranular (RSCd) and granular (RSCg). The current study sought to identify their roles and underlying brain network mechanisms during the encoding processing of the rat CFC model. Rats with pharmacologically inactivated RSCd, RSCg, and corresponding controls underwent contextual fear conditioning. [18F]-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scanning was performed for each animal. The 5-h and 24-h retrieval were followed to test the formation of contextual memory. Graph theoretic tools were used to identify the brain metabolic network involved in encoding phase, and changes of nodal (brain region) properties linked, respectively, to disturbed RSCd and RSCg were analyzed. Impaired retrieval occurred in disturbed RSCd animals, not in RSCg ones. The RSC, hippocampus (Hip), amygdala (Amy), piriform cortex (Pir), and visual cortex (VC) are hub nodes of the brain-wide network for contextual fear memory encoding in rats. Nodal degree and efficiency of hippocampus and its connectivity with amygdala, Pir, and VC were decreased in rats with disturbed RSCd, while not in those with suppressed RSCg. The RSC plays its role in contextual fear memory encoding mainly relying on its RSCd part, whose condition would influence the activity of the hippocampal-amygdalar system.

A Temporal Activity of CA1 Neurons Underlying Short-Term Memory for Social Recognition Altered in PTEN Mouse Models of Autism Spectrum Disorder.

Memory-guided social recognition identifies someone from previous encounters or experiences, but the mechanisms of social memory remain unclear. Here, we find that a short-term memory from experiencing a stranger mouse lasting under 30 min interval is essential for subsequent social recognition in mice, but that interval prolonged to hours by replacing the stranger mouse with a familiar littermate. Optogenetic silencing of dorsal CA1 neuronal activity during trials or inter-trial intervals disrupted short-term memory-guided social recognition, without affecting the ability of being sociable or long-term memory-guided social recognition. Postnatal knockdown or knockout of autism spectrum disorder (ASD)-associated phosphatase and tensin homolog (PTEN) gene in dorsal hippocampal CA1 similarly impaired neuronal firing rate in vitro and altered firing pattern during social recognition. These PTEN mice showed deficits in social recognition with stranger mouse rather than littermate and exhibited impairment in T-maze spontaneous alternation task for testing short-term spatial memory. Thus, we suggest that a temporal activity of dorsal CA1 neurons may underlie formation of short-term memory to be critical for organizing subsequent social recognition but that is possibly disrupted in ASD.

Ferulic Acid Ameliorates Alzheimer's Disease-like Pathology and Repairs Cognitive Decline by Preventing Capillary Hypofunction in APP/PS1 Mice.

Brain capillaries are crucial for cognitive functions by supplying oxygen and other nutrients to and removing metabolic wastes from the brain. Recent studies have demonstrated that constriction of brain capillaries is triggered by beta-amyloid (Aß) oligomers via endothelin-1 (ET1)-mediated action on the ET1 receptor A (ETRA), potentially exacerbating Aß plaque deposition, the primary pathophysiology of Alzheimer's disease (AD). However, direct evidence is still lacking whether changes in brain capillaries are causally involved in the pathophysiology of AD. Using APP/PS1 mouse model of AD (AD mice) relative to age-matched negative littermates, we identified that reductions of density and diameter of hippocampal capillaries occurred from 4 to 7 months old while Aß plaque deposition and spatial memory deficit developed at 7 months old. Notably, the injection of ET1 into the hippocampus induced early Aß plaque deposition at 5 months old in AD mice. Conversely, treatment of ferulic acid against the ETRA to counteract the ET1-mediated vasoconstriction for 30 days prevented reductions of density and diameter of hippocampal capillaries as well as ameliorated Aß plaque deposition and spatial memory deficit at 7 months old in AD mice. Thus, these data suggest that reductions of density and diameter of hippocampal capillaries are crucial for initiating Aß plaque deposition and spatial memory deficit at the early stages, implicating the development of new therapies for halting or curing memory decline in AD.

Developing of Focal Ischemia in the Hippocampus or the Amygdala Reveals a Regional Compensation Rule for Fear Memory Acquisition.

Circuit compensation is often observed in patients with acute ischemic stroke, suggesting the importance of the interaction between brain regions. Also, contextual fear memory is an association between multisensory contexts and fearful stimuli, for which the interaction between the hippocampus and the amygdala is believed to be critical. To understand how focal ischemia in one region could influence the other region, we used a modified photo-thrombosis to induce focal ischemia in the hippocampus or the amygdala or both in freely-moving rats. We found that the learning curve and short-term memory (STM) were not affected in the rats although focal ischemia was induced 5 h before learning in either the hippocampus or the amygdala; these were impaired by the induction of ischemia in both the regions. Furthermore, the learning curve and STM were impaired when ischemia was induced 24 h before learning in either the hippocampus or the amygdala when the synaptic transmission was altered in one region because of ischemia in the other region. These results suggest that the circuit compensation between the hippocampus and the amygdala is critical for fear memory acquisition.

ZFP804A mutant mice display sex-dependent schizophrenia-like behaviors.

Genome-wide association studies uncovered the association of ZNF804A (Zinc-finger protein 804A) with schizophrenia (SZ). In vitro data have indicated that ZNF804A might exert its biological roles by regulating spine and neurite morphogenesis. However, no in vivo data are available for the role of ZNF804A in psychiatric disorders in general, SZ in particular. We generated ZFP804A mutant mice, and they showed deficits in contextual fear and spatial memory. We also observed the sensorimotor gating impairment, as revealed by the prepulse inhibition test, but only in female ZFP804A mutant mice from the age of 6 months. Notably, the PPI difference between the female mutant and control mice was no longer existed with the administration of Clozapine or after the ovariectomy. Hippocampal long-term potentiation was normal in both genders of the mutant mice. Long-term depression was absent in male mutants, but facilitated in the female mutants. Protein levels of hippocampal serotonin-6 receptor and GABAB1 receptor were increased, while those of cortical dopamine 2 receptor were decreased in the female mutants with no obvious changes in the male mutants. Moreover, the spine density was reduced in the cerebral cortex and hippocampus of the mutant mice. Knockdown of ZFP804A impaired the neurite morphogenesis of cortical and hippocampal neurons, while its overexpression enhanced neurite morphogenesis only in the cortical neurons in vitro. Our data collectively support the idea that ZFP804A/ZNF804A plays important roles in the cognitive functions and sensorimotor gating, and its dysfunction may contribute to SZ, particularly in the female patients.

Antidepressant effect of venlafaxine in chronic unpredictable stress: Evidence of the involvement of key enzymes responsible for monoamine neurotransmitter synthesis and metabolism.

A number of studies have linked abnormalities in the function of the serotonergic and noradrenergic systems to the pathophysiology of depression. It has been reported that selective serotonin reuptake inhibitors promote the expression of tryptophan hydroxylase (TPH), which is involved in the synthesis of serotonin. However, limited evidence of TPH alteration has been found in selective serotonin and noradrenaline reuptake inhibitors (SNRIs), and more key enzymes need to be investigated. The aim of the present study was to determine whether venlafaxine (VLX; a classical SNRI) regulates TPH and other key enzymes responsible for the synthesis and metabolism of monoaminergic transmitters in rats with chronic unpredictable stress (CUS). The present results suggested that CUS­exposed rats exhibited decreased locomotor activity in the open­field test and increased immobility time in the forced swim test, as compared with the controls. Pretreatment with VLX (20 mg/kg) significantly increased locomotor activity and reduced immobility time in the CUS­exposed rats. In addition, VLX (20 mg/kg) treatment prevented the CUS­induced reduction in tyrosine hydroxylase and TPH expression in the cortex and hippocampus. Furthermore, VLX alleviated the CUS­induced oxidative stress in the serum, cortex and hippocampus. However, VLX administration did not have an effect on indoleamine­2,3­dioxygenase overexpression in the hippocampus. It was therefore concluded that the regulation of abnormalities in the synthesis and metabolism of monoaminergic transmitters may be associated with the antidepressant effects of VLX, suggesting that multimodal pharmacological treatments can efficiently treat depression.

Antidepressant mechanisms of venlafaxine involving increasing histone acetylation and modulating tyrosine hydroxylase and tryptophan hydroxylase expression in hippocampus of depressive rats.

Venlafaxine (VEN) is a widely used antidepressant as a serotonin-reuptake and norepinephrine-reuptake inhibitor. It is used primarily in depression, especially with generalized anxiety disorder or chronic pain. This medicine is of interest because its mechanisms involved multiple aspects. In the current study, the antidepressant action of VEN was investigated by studying the histone acetylation and expression of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) in rats exposed to chronic unpredicted stress (CUS) for 28 days. Male Sprague-Dawley rats were divided into a control group, VEN-treated control group, CUS group, and VEN-treated CUS group. VEN (23.4 mg/kg once daily) was administered to rats by intragastric gavage, whereas the same volume of vehicle was given to rats in the control and model groups. Rat behaviors, acetylated H3 at lysine 9 (acH3K9), acetylated H3 at lysine 14 (acH3K14), acetylated H4 at lysine 12 (acH4K12), histone deacetylase 5, and TH and TPH expression in the hippocampus were determined. Chronic VEN treatment significantly relieved the anxiety- and depression-like behaviors, prevented the increase of histone deacetylase 5 expression and decrease of acH3K9 level, and promoted TH and TPH protein expression in the hippocampus of CUS rats. The results suggest that the preventive antidepressant mechanism of VEN is partly involved in the blocking effects on histone de-acetylated modification and then increasing TH, TPH expression.

The interhemispheric CA1 circuit governs rapid generalisation but not fear memory.

Encoding specificity theory predicts most effective recall by the original conditions at encoding, while generalization endows recall flexibly under circumstances which deviate from the originals. The CA1 regions have been implicated in memory and generalization but whether and which locally separated mechanisms are involved is not clear. We report here that fear memory is quickly formed, but generalization develops gradually over 24 h. Generalization but not fear memory is impaired by inhibiting ipsilateral (ips) or contralateral (con) CA1, and by optogenetic silencing of the ipsCA1 projections onto conCA1. By contrast, in vivo fEPSP recordings reveal that ipsCA1-conCA1 synaptic efficacy is increased with delay over 24 h when generalization is formed but it is unchanged if generalization is disrupted. Direct excitation of ipsCA1-conCA1 synapses using chemogenetic hM3Dq facilitates generalization formation. Thus, rapid generalization is an active process dependent on bilateral CA1 regions, and encoded by gradual synaptic learning in ipsCA1-conCA1 circuit.

Abnormal modification of histone acetylation involved in depression-like behaviors of rats induced by chronically unpredicted stress.

Depression is a complex multifactorial mental disorder. Its etiology involves many factors such as social environments, genetics, and psychology. Recent studies have shown that epigenetic modification may be associated with depression. Histone acetylation is one of the main mechanisms of epigenetic modification and plays an important role in genetic expression. In this study, we investigated the role of histone acetylation in the depression-like behaviors of rats undergoing chronically unpredicted stress (CUS) by detecting the mRNA and protein expression of histone deacetylase 5, cAMP-response element-binding protein, and the level of histone acetylated modification of H3K14, H3K23, and H4K16 in the prefrontal cortex and hippocampus of the rats. The results showed that significantly increasing depression-like behaviors were observed with a decreasing histone acetylated modification level, especially on acytelated-H3K14, acytelated-H3K23, and acytelated-H4K16, upregulating histone deacetylase 5 expression and downregulating cAMP-response element-binding protein expression in CUS rats, compared with control rats. The results indicate that the decrease in the histone acetylation modification level may be partly involved in the mechanism of depression-like behaviors of rats induced by CUS.

The Small GTPase Rac1 Contributes to Extinction of Aversive Memories of Drug Withdrawal by Facilitating GABAA Receptor Endocytosis in the vmPFC.

Extinction of aversive memories has been a major concern in neuropsychiatric disorders, such as anxiety disorders and drug addiction. However, the mechanisms underlying extinction of aversive memories are not fully understood. Here, we report that extinction of conditioned place aversion (CPA) to naloxone-precipitated opiate withdrawal in male rats activates Rho GTPase Rac1 in the ventromedial prefrontal cortex (vmPFC) in a BDNF-dependent manner, which determines GABAA receptor (GABAAR) endocytosis via triggering synaptic translocation of activity-regulated cytoskeleton-associated protein (Arc) through facilitating actin polymerization. Active Rac1 is essential and sufficient for GABAAR endocytosis and CPA extinction. Knockdown of Rac1 expression within the vmPFC of rats using Rac1-shRNA suppressed GABAAR endocytosis and CPA extinction, whereas expression of a constitutively active form of Rac1 accelerated GABAAR endocytosis and CPA extinction. The crucial role of GABAAR endocytosis in the LTP induction and CPA extinction is evinced by the findings that blockade of GABAAR endocytosis by a dynamin function-blocking peptide (Myr-P4) abolishes LTP induction and CPA extinction. Thus, the present study provides first evidence that Rac1-dependent GABAAR endocytosis plays a crucial role in extinction of aversive memories and reveals the sequence of molecular events that contribute to learning experience modulation of synaptic GABAAR endocytosis.SIGNIFICANCE STATEMENT This study reveals that Rac1-dependent GABAAR endocytosis plays a crucial role in extinction of aversive memories associated with drug withdrawal and identifies Arc as a downstream effector of Rac1 regulations of synaptic plasticity as well as learning and memory, thereby suggesting therapeutic targets to promote extinction of the unwanted memories.

Protective efficacy of a single salvianolic acid A treatment on photothrombosis-induced sustained spatial memory impairments.

With respect to the high burden of ischemic stroke and the absence of pharmacological treatment for promoting rehabilitation, promising candidates with specific effects on long-term functional recovery are highly desired. Candidates need reasonable experimental paradigms to evaluate the long-term functional outcome focused on ischemia-induced sensorimotor and memory deficits. "Danshen", a traditional Chinese herb, has long been used to treat coronary and cerebral vascular diseases as well as dementia. Salvianolic acid A (SAA), one of the major active ingredients of Danshen, was demonstrated to be effective in protecting against cerebral ischemic injury. Here, employing an experimental stroke model induced by photothrombosis in the unilateral frontal cortex of rats, we investigated whether SAA has long-term protective effects on ischemia-induced sensorimotor and memory deficits in our behavioral tests. The results indicated that a single SAA treatment improved the cortical ischemia-induced sensorimotor deficits during 15 days' cylinder test period, and alleviated ischemia-induced sustained spatial memory impairments during the 2 months' dependent Morris Water Maze (MWM) tests. In addition, either ischemic injury or SAA treatment did not show any changes compared with sham group in other behavioral tests including rotarod tests, swimming speed in MWM tests, open field tests, elevated plus maze tests, treadmill tests and forced swimming tests. The results reveal that the cognitive deficits are not the results of animal's anxiety or confounding motor impairments. Overall, the present paradigm appears suitable for the preclinical evaluation of the long-term effects of pharmacological treatments on ischemic stroke. Meanwhile, SAA might have therapeutic potential for the treatment of memory deficits associated with ischemic stroke.

Abnormal levels of seven amino neurotransmitters in depressed rat brain and determination by HPLC-FLD.

The determination of amino acids with actions like neurotransmitters or modulators has been increasingly important for diagnosis in many neuropsychiatric diseases. A rapid and simple high-performance liquid chromatography with fluorescence detection method was developed for simultaneous determination of seven amino acids: aspartate (Asp), glutamate (Glu), serine (Ser), glutamine (Gln), glycine (Gly), taurine (Tau) and γ-aminobutyric` acid (GABA). Homoserine was used as an internal standard. The analysis was performed on a BDS column with methanol and 50 mm sodium acetate solution (pH 6.5) using a simple gradient elution. Several parameters of the developed method were validated including linearity, accuracy, precision, extraction recovery and stability, which were within the acceptable range. The method was successfully applied to determination of real samples: hippocampus and cortex in depressed rats exposed to chronically unpredictable stress in order to study if there existed differences in the seven amino acids levels between depressed rats and control. The results showed that Asp, Gly, Tau and GABA significantly decreased with increasing Gln in the hippocampus of depressed rats, compared with that of the control group, among which obviously lower level of Asp and higher level of Gln in cortex were observed. The analytical method and the results could be useful for clinical diagnosis and further insight into pathophysiological mechanism of depression.

Infliximab ameliorating depression-like behavior through inhibiting the activation of the IDO-HAAO pathway mediated by tumor necrosis factor-α in a rat model.

In recent years, some studies have suggested that the activation of inflammatory system plays a role in the occurrence of depression. Tumor necrosis factor-α (TNF-α), as one of the preinflammatory cytokines, has been reported to be involved in the occurrence of various diseases including depression. Infliximab, an antagonist of TNF-α, is usually used to treat some autoimmune diseases such as Crohn's disease and can perhaps be used to treat other diseases. In this study, the antidepressant effect and a possible mechanism of infliximab were investigated by studying the depression-like behavior and expression of TNF-α, indoleamine 2, 3-dioxygenase (IDO), and 3-hydroxyl amino acid oxygenase (HAAO) from the cortex and hippocampus in rat exposed to chronic unpredicted stress. Forty male Sprague-Dawley rats were divided into a control group (CG), an infliximab-treated control group, a model group (MG), and an infliximab-treated model group (IFXM). Infliximab (5 mg/kg once week) was administered to the infliximab-treated control group and IFXM rats by an intraperitoneal injection, whereas an equivalent volume of vehicle was administered to CG and MG rats. Rat behaviors and the expression of TNF-α, IDO, and HAAO in the cortex and hippocampus were determined. It was found that a significant relief in depression-like behaviors was observed with a downregulation of TNF-α, IDO, and HAAO expression in the IFXM rats compared with MG rats. The results show the antidepressant effect of infliximab and suggest that its mechanism is partly related to inhibition of IDO-HAAO pathway activation mediated by TNF-α in rat brain.

Corticosterone regulates fear memory via Rac1 activity in the hippocampus.

Stressful events can generate enduring memories, which may induce certain psychiatric disorders such as post-traumatic stress disorder (PTSD). However, the underlying molecular mechanisms in these processes remain unclear. In this study, we examined whether the active form of the small G protein Rac1, Rac1-GTP, is involved in fear memory. Firstly, we detected the time course changes of Rac1-GTP after foot shocks (a strong stressor) and exogenous corticosterone (CORT) treatment. The data showed that stress and CORT induced the downregulation of Rac1-GTP in the hippocampus. Changes in the serum CORT level were negatively correlated with the level of Rac1-GTP. Additionally, a glucocorticoid receptor antagonist, RU38486, not only recovered the expression of Rac1-GTP but also impaired fear memory. Furthermore, systemic administration of NSC23766, an inhibitor of Rac1-GTP, improved fear memory at 1.5 and 24h. Therefore, Rac1 activity plays a critical role in stress-related cognition and may be a potential target in stress-related disorders.