Calcium/calmodulin-dependent kinase IV contributes to translation-dependent early synaptic potentiation in the anterior cingulate cortex of adult mice

ARID1B controls transcriptional programs of axon projection in an organoid model of the human corpus callosum

Mutations in ARID1B, a member of the mSWI/SNF complex, cause severe neurodevelopmental phenotypes with elusive mechanisms in humans. The most common structural abnormality in the brain of ARID1B patients is agenesis of the corpus callosum (ACC), characterized by the absence of an interhemispheric white matter tract that connects distant cortical regions. Here, we find that neurons expressing SATB2, a determinant of callosal projection neuron (CPN) identity, show impaired maturation in ARID1B+/- neural organoids. Molecularly, a reduction in chromatin accessibility of genomic regions targeted by TCF-like, NFI-like, and ARID-like transcription factors drives the differential expression of genes required for corpus callosum (CC) development. Through an in vitro model of the CC tract, we demonstrate that this transcriptional dysregulation impairs the formation of long-range axonal projections, causing structural underconnectivity. Our study uncovers new functions of the mSWI/SNF during human corticogenesis, identifying cell-autonomous axonogenesis defects in SATB2+ neurons as a cause of ACC in ARID1B patients.

Synaptic Plasticity in the Pain-Related Cingulate and Insular Cortex

Cumulative animal and human studies have consistently demonstrated that two major cortical regions in the brain, namely the anterior cingulate cortex (ACC) and insular cortex (IC), play critical roles in pain perception and chronic pain. Neuronal synapses in these cortical regions of adult animals are highly plastic and can undergo long-term potentiation (LTP), a phenomenon that is also reported in brain areas for learning and memory (such as the hippocampus). Genetic and pharmacological studies show that inhibiting such cortical LTP can help to reduce behavioral sensitization caused by injury as well as injury-induced emotional changes. In this review, we will summarize recent progress related to synaptic mechanisms for different forms of cortical LTP and their possible contribution to behavioral pain and emotional changes.

Nrf2 improves hippocampal synaptic plasticity, learning and memory through the circ-Vps41/miR-26a-5p/CaMKIV regulatory network

Antioxidant response transcription factor nuclear factor erythroid-2-related factor 2 (Nrf2/Nfe2l2) is a neuroprotective agent in learning and memory impairment. This study provides a new perspective to explore the regulatory mechanisms of Nrf2. Here, we found that Nrf2 regulated circular RNA circ-Vps41 to increase hippocampal synaptic plasticity; Nrf2 bound the Vps41 promoter to activate transcription of the Vps41 gene and promote expression of circ-Vps41; circ-Vps41 positively correlated with Nrf2, synaptic plasticity, and learning and memory but negatively correlated with reactive oxygen species; and Nrf2 promoted CaMKIV expression by increasing levels of circ-Vps41, which can absorb miR-26a-5p that targets CaMKIV. Our findings revealed a new circRNA-based regulatory network regulated by Nrf2 and provided novel insights into the potential mechanism involved in the improvement of learning and memory impairment.

Sevoflurane induces inflammation of microglia in hippocampus of neonatal rats by inhibiting Wnt/β-Catenin/CaMKIV pathway

OBJECTIVE

To investigate the effect of sevoflurane on inflammation of microglia in hippocampus of neonatal rats, and to investigate whether the related mechanism is related to Wnt/β-Catenin/CaMKIV pathway.

METHODS

Neonatal rats were anesthetized with 2% or 3% sevoflurane for 4 h a day for 3 consecutive days. Water maze test was used to detect the effect of sevoflurane anesthesia on memory function of neonatal rats. H&E and Nissl staining were used to observe the pathological damage of hippocampal area of neonatal rats induced by sevoflurane anesthesia. The expression of microglial marker Iba-1 was detected by Immunofluorescence. Immunofluorescence and WB were used to detect the expression CD32b, CD86, TNF-α, IL-6, Wnt3a, β-Catenin and CaMKIV in hippocampus. To further explore the related mechanism, Wnt-3α inhibitor and activator was treated to study the effect of sevoflurane on microglial inflammation in hippocampus of neonatal rats.

RESULTS

Sevoflurane anesthesia significantly increased escape latency time, reduced platform crossing times, and damaged the learning and memory ability of neonatal rats. H&E and Nissl staining results showed that sevoflurane anesthesia caused obvious damage to the hippocampus of neonatal rats. Sevoflurane anesthesia promoted the expression of Iba-1 and activated microglia. Sevoflurane anesthesia not only significantly increased the positive expression of CD32b, CD86, TNF-α and IL-6, but also decreased the expression of Wnt3a, β-Catenin and CaMKIV. These results suggested that sevoflurane inhibited Wnt/β-Catenin/CaMKIV pathway.

CONCLUSION

Sevoflurane induces inflammation of microglia in hippocampus of neonatal rats by inhibiting Wnt/β-Catenin/CaMKIV pathway.

The Calcium/Calmodulin-Dependent Kinases II and IV as Therapeutic Targets in Neurodegenerative and Neuropsychiatric Disorders

CaMKII and CaMKIV are calcium/calmodulin-dependent kinases playing a rudimentary role in many regulatory processes in the organism. These kinases attract increasing interest due to their involvement primarily in memory and plasticity and various cellular functions. Although CaMKII and CaMKIV are mostly recognized as the important cogs in a memory machine, little is known about their effect on mood and role in neuropsychiatric diseases etiology. Here, we aimed to review the structure and functions of CaMKII and CaMKIV, as well as how these kinases modulate the animals’ behavior to promote antidepressant-like, anxiolytic-like, and procognitive effects. The review will help in the understanding of the roles of the above kinases in the selected neurodegenerative and neuropsychiatric disorders, and this knowledge can be used in future drug design.

Pre-LTP requires extracellular signal-regulated kinase in the ACC

The extracellular signal-regulated kinase is an important protein kinase for cortical plasticity. Long-term potentiation in the anterior cingulate cortex is believed to play important roles in chronic pain, fear, and anxiety. Previous studies of extracellular signal-regulated kinase are mainly focused on postsynaptic form of long-term potentiation (post-long-term potentiation). Little is known about the relationship between extracellular signal-regulated kinase and presynaptic long-term potentiation (pre-long-term potentiation) in cortical synapses. In this study, we examined whether pre-long-term potentiation in the anterior cingulate cortex requires the activation of presynaptic extracellular signal-regulated kinase. We found that p42/p44 mitogen-activated protein kinase inhibitors, PD98059 and U0126, suppressed the induction of pre-long-term potentiation. By contrast, these inhibitors did not affect the maintenance of pre-long-term potentiation. Using pharmacological inhibitors, we found that pre-long-term potentiation recorded for 1 h did not require transcriptional or translational processes. Our results strongly indicate that the activation of presynaptic extracellular signal-regulated kinase is required for the induction of pre-long-term potentiation, and this involvement may explain the contribution of extracellular signal-regulated kinase to mood disorders.

Synaptic Plasticity, a Prominent Contributor to the Anxiety in Fragile X Syndrome

Fragile X syndrome (FXS) is an inheritable neuropsychological disease caused by expansion of the CGG trinucleotide repeat affecting the fmr1 gene on X chromosome, resulting in silence of the fmr1 gene and failed expression of FMRP. Patients with FXS suffer from cognitive impairment, sensory integration deficits, learning disability, anxiety, autistic traits, and so forth. Specifically, the morbidity of anxiety in FXS individuals remains high from childhood to adulthood. By and large, it is common that the change of brain plasticity plays a key role in the progression of disease. But for now, most studies excessively emphasized the one-sided factor on the change of synaptic plasticity participating in the generation of anxiety during the development of FXS. Here we proposed an integrated concept to acquire better recognition about the details of this process.

Electroacupuncture alleviates retrieval of pain memory and its effect on phosphorylation of cAMP response element-binding protein in anterior cingulate cortex in rats

Background

Recent evidence suggests that persistent pain and recurrent pain are due to the pain memory which is related to the phosphorylation of cAMP response element-binding protein (p-CREB) in anterior cingulate cortex (ACC). Eletroacupuncture (EA), as a complementary Chinese medical procedure, has a significant impact on the treatment of pain and is now considered as a mind-body therapy.

Methods

The rat model of pain memory was induced by two injections of carrageenan into the paws, which was administered separately by a 14-day interval, and treated with EA therapy. The paw withdrawal thresholds (PWTs) of animals were measured and p-CREB expressions in ACC were detected by using immunofluorescence (IF) and electrophoretic mobility shift assay (EMSA). Statistical comparisons among different groups were made by one-way, repeated-measures analysis of variance (ANOVA).

Results

The second injection of carrageenan caused the decrease of PWTs in the non-injected hind paw. EA stimulation applied prior to the second injection, increased the values of PWTs. In ACC, the numbers of p-CREB positive cells were significantly increased in pain memory model rats, which were significantly reduced by EA. EMSA results showed EA also down-regulated the combining capacity of p-CREB with its DNA. Furthermore, the co-expression of p-CREB with GFAP, OX-42, or NeuN in ACC was strengthened in the pain memory model rats. EA inhibited the co-expression of p-CREB with GFAP or OX-42, but not NeuN in ACC.

Conclusions

The present results suggest the retrieval of pain memory could be alleviated by the pre-treatment of EA, which is at least partially attributed to the down-regulated expression and combining capacity of p-CREB and the decreased expression of p-CREB in astrocytes and microglia cells.

Adenylyl cyclase subtype 1 is essential for late-phase long term potentiation and spatial propagation of synaptic responses in the anterior cingulate cortex of adult mice

Long-term potentiation (LTP) is a key cellular mechanism for pathological pain in the central nervous system. LTP contains at least two different phases: early-phase LTP (E-LTP) and late-phase LTP (L-LTP). Among several major cortical areas, the anterior cingulate cortex (ACC) is a critical brain region for pain perception and its related emotional changes. Periphery tissue or nerve injuries cause LTP of excitatory synaptic transmission in the ACC. Our previous studies have demonstrated that genetic deletion of calcium-stimulated adenylyl cyclase 1 (AC1) or pharmacological application of a selective AC1 inhibitor NB001 blocked E-LTP in the ACC. However, the effect of AC1 on L-LTP, which requires new protein synthesis and is important for the process of chronic pain, has not been investigated. Here we tested the effects of NB001 on the ACC L-LTP and found that bath application of NB001 (0.1 μM) totally blocked the induction of L-LTP and recruitment of cortical circuitry without affecting basal excitatory transmission. In contrast, gabapentin, a widely used analgesic drug for neuropathic pain, did not block the induction of L-LTP and circuitry recruitment even at a high concentration (100 μM). Gabapentin non-selectively decreased basal synaptic transmission. Our results provide strong evidence that the selective AC1 inhibitor NB001 can be used to inhibit pain-related cortical L-LTP without affecting basal synaptic transmission. It also provides basic mechanisms for possible side effects of gabapentin in the central nervous system and its ineffectiveness in some patients with neuropathic pain.

Pharmacological rescue of cortical synaptic and network potentiation in a mouse model for fragile X syndrome

Fragile X syndrome, caused by the mutation of the Fmr1 gene, is characterized by deficits of attention and learning ability. In the hippocampus of Fmr1 knockout mice (KO), long-term depression is enhanced whereas long-term potentiation (LTP) including late-phase LTP (L-LTP) is reduced or unaffected. Here we examined L-LTP in the anterior cingulate cortex (ACC) in Fmr1 KO mice by using a 64-electrode array recording system. In wild-type mice, theta-burst stimulation induced L-LTP that does not occur in all active electrodes/channels within the cingulate circuit and is typically detected in ∼75% of active channels. Furthermore, L-LTP recruited new responses from previous inactive channels. Both L-LTP and the recruitment of inactive responses were blocked in the ACC slices of Fmr1 KO mice. Bath application of metabotropic glutamate receptor 5 (mGluR5) antagonist or glycogen synthase kinase-3 (GSK3) inhibitors rescued the L-LTP and network recruitment. Our results demonstrate that loss of FMRP will greatly impair L-LTP and recruitment of cortical network in the ACC that can be rescued by pharmacological inhibition of mGluR5 or GSK3. This study is the first report of the network properties of L-LTP in the ACC, and provides basic mechanisms for future treatment of cortex-related cognitive defects in fragile X patients.

Uncoupling PSD-95 interactions leads to rapid recovery of cortical function after focal stroke

Since the most significant ischemic sequelae occur within hours of stroke, it is necessary to understand how neuronal function changes during this time. While histologic and behavioral models show the extent of stroke-related damage, only in vivo recordings can illustrate changes in brain activity during stroke and validate effectiveness of neuroprotective compounds. Spontaneous and evoked field potentials (fEPs) were recorded in the deep layers of the cortex with a linear microelectrode array for 3 hours after focal stroke in anesthetized rats. Tat-NR2B9c peptide, which confers neuroprotection by uncoupling the PSD-95 protein from N-methyl-D-aspartate receptor (NMDAR), was administered 5 minutes before ischemia. Evoked field potentials were completely suppressed within 3 minutes of infarct in all ischemic groups. Evoked field potential recovery after stroke in rats treated with Tat-NR2B9c (83% of baseline) was greater compared with stroke-only (61% of baseline) or control peptide (Tat-NR2B-AA; 67% of baseline) groups (P<0.001). Electroencephalography (EEG) power was higher in Tat-NR2B9c-treated animals at both 20 minutes and 1 hour (50% and 73% of baseline, respectively) compared with stroke-only and Tat-NR2B-AA-treated rats (P<0.05). Tat-NR2B9c significantly reduces stroke-related cortical dysfunction as evidenced by greater recovery of fEPs and EEG power; illustrating the immediate effects of the compound on poststroke brain function.

Long-term potentiation of synaptic transmission in the adult mouse insular cortex: multielectrode array recordings

The insular cortex (IC) is widely believed to be an important forebrain structure involved in cognitive and sensory processes such as memory and pain. However, little work has been performed at the cellular level to investigate the synaptic basis of IC-related brain functions. To bridge the gap, the present study was designed to characterize the basic synaptic mechanisms for insular long-term potentiation (LTP). Using a 64-channel recording system, we found that an enduring form of late-phase LTP (L-LTP) could be reliably recorded for at least 3 h in different layers of IC slices after theta burst stimulation. The induction of insular LTP is protein synthesis dependent and requires activation of both GluN2A and GluN2B subunits of the NMDA receptor, L-type voltage-gated calcium channels, and metabotropic glutamate receptor 1. The paired-pulse facilitation ratio was unaffected by insular L-LTP induction, and expression of insular L-LTP required the recruitment of postsynaptic calcium-permeable AMPA receptors. Our results provide the first in vitro report of long-term multichannel recordings of L-LTP in the IC in adult mice and suggest its potential important roles in insula-related memory and chronic pain.

Running-induced epigenetic and gene expression changes in the adolescent brain

Physical exercise is associated with positive neural functioning. Here we examined the gene expression consequences of 1 week of voluntary wheel running in adolescent male mice. We assayed expression levels of genes associated with synaptic plasticity, signaling pathways, and epigenetic modifying enzymes. Two regions were examined: the hippocampus, which is typically examined in exercise studies, and the cerebellum, an area directly involved in motor control and learning. After 1 week of exercise, global acetylation of histone 3 was increased in both brain regions. Interestingly this was correlated with increased brain derived neural growth factor in the hippocampus, as noted in many other studies, but only a trend was found in cerebellum. Differences and similarities between the two areas were noted for genes encoding functional proteins. In contrast, the expression pattern of DNA methyltransferases (Dnmts) and histone deacetylases (Hdacs), genes that influence DNA methylation and histone modifications in general, decreased in both regions with exercise. We hypothesize that epigenetic mechanisms, involving many of the genes assessed here, are essential for the positive affects of exercise on behavior and suspect these data have relevance for adolescent boys.

Upregulation of transmitter release probability improves a conversion of synaptic analogue signals into neuronal digital spikes

Action potentials at the neurons and graded signals at the synapses are primary codes in the brain. In terms of their functional interaction, the studies were focused on the influence of presynaptic spike patterns on synaptic activities. How the synapse dynamics quantitatively regulates the encoding of postsynaptic digital spikes remains unclear. We investigated this question at unitary glutamatergic synapses on cortical GABAergic neurons, especially the quantitative influences of release probability on synapse dynamics and neuronal encoding. Glutamate release probability and synaptic strength are proportionally upregulated by presynaptic sequential spikes. The upregulation of release probability and the efficiency of probability-driven synaptic facilitation are strengthened by elevating presynaptic spike frequency and Ca²⁺. The upregulation of release probability improves spike capacity and timing precision at postsynaptic neuron. These results suggest that the upregulation of presynaptic glutamate release facilitates a conversion of synaptic analogue signals into digital spikes in postsynaptic neurons, i.e., a functional compatibility between presynaptic and postsynaptic partners.

Rapid synaptic potentiation within the anterior cingulate cortex mediates trace fear learning

Although the cortex has been extensively studied in long-term memory storage, less emphasis has been placed on immediate cortical contributions to fear memory formation. AMPA receptor plasticity is strongly implicated in learning and memory, and studies have identified calcium permeable AMPA receptors (CP-AMPARs) as mediators of synaptic strengthening. Trace fear learning engages the anterior cingulate cortex (ACC), but whether plastic events occur within the ACC in response to trace fear learning, and whether GluN2B subunits are required remains unknown. Here we show that the ACC is necessary for trace fear learning, and shows a rapid 20% upregulation of membrane AMPA receptor GluA1 subunits that is evident immediately after conditioning. Inhibition of NMDA receptor GluN2B subunits during training prevented the upregulation, and disrupted trace fear memory retrieval 48 h later. Furthermore, intra-ACC injections of the CP-AMPAR channel antagonist, 1-naphthylacetyl spermine (NASPM) immediately following trace fear conditioning blocked 24 h fear memory retrieval. Accordingly, whole cell patch clamp recordings from c-fos positive and c-fos negative neurons within the ACC in response to trace fear learning revealed an increased sensitivity to NASPM in recently activated neurons that was reversed by reconsolidation update extinction. Our results suggest that trace fear learning is mediated through rapid GluN2B dependent trafficking of CP-AMPARs, and present in vivo evidence that CP-AMPAR activity within the ACC immediately after conditioning is necessary for subsequent memory consolidation processes.

Hyperalgesia by synaptic long-term potentiation (LTP): an update

Long-term potentiation of synaptic strength (LTP) in nociceptive pathways shares principle features with hyperalgesia including induction protocols, pharmacological profile, neuronal and glial cell types involved and means for prevention. LTP at synapses of nociceptive nerve fibres constitutes a contemporary cellular model for pain amplification following trauma, inflammation, nerve injury or withdrawal from opioids. It provides a novel target for pain therapy. This review summarizes recent progress which has been made in unravelling the properties and functions of LTP in the nociceptive system and in identifying means for its prevention and reversal.

Interplay of amygdala and cingulate plasticity in emotional fear

The amygdala is known to be a critical brain region for emotional fear. It is believed that synaptic plasticity within the amygdala is the cellular basis of fear memory. Recent studies demonstrate that cortical areas such as the prefrontal cortex (PFC) and anterior cingulate cortex (ACC) may also contribute to the formation of fear memory, including trace fear memory and remote fear memory. At synaptic level, fear conditioning also triggers plastic changes within the cortical areas immediately after the condition. These results raise the possibility that certain forms of synaptic plasticity may occur within the cortex while synaptic potentiation takes place within synapses in the hippocampus and amygdala. This hypothesis is supported by electrophysiological evidence obtained from freely moving animals that neurons in the hippocampus/amygdala fire synchronous activities with cortical neurons during the learning. To study fear-related synaptic plasticity in the cortex and its functional connectivity with neurons in the amygdala and hippocampus will help us understand brain mechanisms of fear and improve clinical treatment of emotional disorders in patients.

Erasing injury-related cortical synaptic potentiation as a new treatment for chronic pain

Synaptic plasticity in the spinal cord and the cortex is believed to be important for the amplification of painful information in chronic pain conditions. The investigation of molecular mechanism responsible for maintaining injury-related plastic changes, such as through the study of long-term potentiation in these structures, provides potential novel targets for designing new medicine for chronic pain. Recent studies using integrative neurobiological approaches demonstrate that protein kinase M zeta (PKMζ) maintains pain-induced persistent changes in the anterior cingulate cortex (ACC), and inhibiting PKMζ by ζ-pseudosubstrate inhibitory peptide produces analgesic effects in animal models of chronic pain. We propose that targeting PKMζ, or its up- or downstream signaling proteins, in the ACC may provide novel clinical treatment for chronic pain.