Loss of long-term depression in the insular cortex after tail amputation in adult mice

Enhanced long-term potentiation in the anterior cingulate cortex of tree shrew

Synaptic plasticity is a key cellular model for learning, memory and chronic pain. Most previous studies were carried out in rats and mice, and less is known about synaptic plasticity in non-human primates. In the present study, we used integrative experimental approaches to study long-term potentiation (LTP) in the anterior cingulate cortex (ACC) of adult tree shrews. We found that glutamate is the major excitatory transmitter and α-amino-3-hydroxy-5-methyl-4-isoxazole-propionicacid (AMPA) receptors mediate postsynaptic responses. LTP in tree shrews was greater than that in adult mice and lasted for at least 5 h. N-methyl-d-aspartic acid (NMDA) receptors, Ca2+ influx and adenylyl cyclase 1 (AC1) contributed to tree shrew LTP. Our results suggest that LTP is a major form of synaptic plasticity in the ACC of primate-like animals. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

Alleviation of migraine related pain and anxiety by inhibiting calcium-stimulating AC1-dependent CGRP in the insula of adult rats

BACKGROUND

Recent animal and clinical findings consistently highlight the critical role of calcitonin gene-related peptide (CGRP) in chronic migraine (CM) and related emotional responses. CGRP antibodies and receptor antagonists have been approved for CM treatment. However, the underlying CGRP-related signaling pathways in the pain-related cortex remain poorly understood.

METHODS

The SD rats were used to establish the CM model by dural infusions of inflammatory soup. Periorbital mechanical thresholds were assessed using von-Frey filaments, and anxiety-like behaviors were observed via open field and elevated plus maze tests. Expression of c-Fos, CGRP and NMDA GluN2B receptors was detected using immunofluorescence and western blotting analyses. The excitatory synaptic transmission was detected by whole-cell patch-clamp recording. A human-used adenylate cyclase 1 (AC1) inhibitor, hNB001, was applied via insula stereotaxic and intraperitoneal injections in CM rats.

RESULTS

The insular cortex (IC) was activated in the migraine model rats. Glutamate-mediated excitatory transmission and NMDA GluN2B receptors in the IC were potentiated. CGRP levels in the IC significantly increased during nociceptive and anxiety-like activities. Locally applied hNB001 in the IC or intraperitoneally alleviated periorbital mechanical thresholds and anxiety behaviors in migraine rats. Furthermore, CGRP expression in the IC decreased after the hNB001 application.

CONCLUSIONS

Our study indicated that AC1-dependent IC plasticity contributes to migraine and AC1 may be a promising target for treating migraine in the future.

Targeting long-term depression of excitatory synaptic transmission for the treatment of neuropathic pain

Injury or disease in the somatosensory nervous system may cause broad molecular changes and lead to neuropathic pain. Excitatory synaptic transmission in somatosensory pathways conveys the somatosensory information from the peripheral to the central nervous system. Long-term effects of excitatory synaptic transmission on the pain pathway contribute to neuropathic pain hypersensitivity. Synaptic strength is dynamically regulated and undergoes bidirectional changes, manifested by two primary forms of synaptic plasticity, long-term potentiation and long-term depression (LTD), which are mediated by insertion and endocytosis of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), respectively. Molecular mechanisms of LTP have been extensively studied; on the other hand, the role of AMPAR endocytosis in the pain-related synaptic enhancement is less well known. Recent research in the anterior cingulate cortex reveals that loss of LTD contributes to the maintenance of neuropathic pain, which provides the novel perspective of the mechanism of LTD also being critical for maintaining neuropathic pain. More importantly, exploring the molecular mechanism of LTD may help with the development of novel analgesic strategies to manage neuropathic pain.

Effects of Neural Mobilization on Sensory Dysfunction and Peripheral Nerve Degeneration in Rats With Painful Diabetic Neuropathy

OBJECTIVE

This study aims to evaluate the effectiveness of neural mobilization (NM) in the management of sensory dysfunction and nerve degeneration related to experimental painful diabetic neuropathy (PDN).

METHODS

This is a pre-clinical animal study performed in the streptozocin-induced diabetic rat model. Three groups were included: a treatment group of rats with PDN receiving NM under anesthesia (PDN-NM, n = 10), a sham treatment group of rats with PDN that received only anesthesia (PDN-Sham, n = 9), and a vehicle control group with nondiabetic animals (Vehicle, n = 10). Rats in the PDN-NM and PDN-Sham groups received 1 treatment session on days 10, 12, and 14 after streptozocin injection, with a 48-hour rest period between sessions. Behavioral tests were performed using von Frey and Plantar tests. Evaluation for peripheral nerve degeneration was performed through measuring protein gene product 9.5-positive intra-epidermal nerve fiber density in hind-paw skin biopsies. All measurements were performed by a blinded investigator.

RESULTS

The behavioral tests showed that a single NM session could reduce hyperalgesia, which was maintained for 48 hours. The second treatment session further improved this treatment effect, and the third session maintained it. These results suggest that it requires multiple treatment sessions to produce and maintain hypoalgesic effects. Skin biopsy analysis showed that the protein gene product 9.5-positive intra-epidermal nerve fiber density was higher on the experimental side of the PDN-NM group compared with the PDN-Sham group, suggesting NM may mitigate the degeneration of peripheral nerves.

CONCLUSION

This study demonstrated that NM may be an effective method to manage experimentally induced PDN, potentially through mitigation of nerve degeneration. Further studies are needed to develop standardized protocols for clinical use.

IMPACT

These findings provide neurophysiological evidence for the use of NM in PDN and can form the basis for the development of physical therapy-based programs in clinics.

Aberrant functional connectivity in insular subregions in somatic depression: a resting-state fMRI study

BACKGROUND

Somatic depression (SD) is different from non-somatic depression (NSD), and insular subregions have been associated with somatic symptoms. However, the pattern of damage in the insular subregions in SD remains unclear. The aim of this study was to use functional connectivity (FC) analyses to explore the bilateral ventral anterior insula (vAI), bilateral dorsal anterior insula (dAI), and bilateral posterior insula (PI) brain circuits in SD patients.

METHODS

The study included 28 SD patients, 30 NSD patients, and 30 matched healthy control (HC) subjects. All participants underwent 3.0 T resting state functional magnetic resonance imaging. FC analyses were used to explore synchronization between insular subregions and the whole brain in the context of depression with somatic symptoms. Pearson correlation analyses were performed to assess relationships between FC values in brain regions showing significant differences and the total and factor scores on the 17-item Hamilton Rating Scale for Depression (HAMD₁₇).

RESULTS

Compared with the NSD group, the SD group showed significantly decreased FC between the left vAI and the right rectus gyrus, right fusiform gyrus, and right angular gyrus; between the right vAI and the right middle cingulate cortex, right precuneus, and right superior frontal gyrus; between the left dAI and the left fusiform gyrus; and between the right dAI and the left postcentral gyrus. Relative to the NSD group, the SD group exhibited increased FC between the left dAI and the left fusiform gyrus. There were no differences in FC between bilateral PI and any brain regions among the SD, NSD, and HC groups. Within the SD group, FC values between the left vAI and right rectus gyrus were positively correlated with cognitive impairment scores on the HAMD₁₇; FC values between the right vAI and right superior frontal gyrus were positively related to the total scores and cognitive impairment scores on the HAMD₁₇ (p < 0.05, uncorrected).

CONCLUSIONS

Aberrant FC between the anterior insula and the frontal and limbic cortices may be one possible mechanism underlying SD.

Restoration of Cingulate Long-Term Depression by Enhancing Non-apoptotic Caspase 3 Alleviates Peripheral Pain Hypersensitivity

Nerve injury in somatosensory pathways may lead to neuropathic pain, which affects the life quality of ∼8% of people. Long-term enhancement of excitatory synaptic transmission along somatosensory pathways contributes to neuropathic pain. Caspase 3 (Casp3) plays a non-apoptotic role in the hippocampus and regulates internalization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits. Whether Casp3-AMPAR interaction is involved in the maintenance of peripheral hypersensitivity after nerve injury remained unknown. Here, we show that nerve injury suppresses long-term depression (LTD) and downregulates Casp3 in the anterior cingulate cortex (ACC). Interfering with interactions between Casp3 and AMPAR subunits or reducing Casp3 activity in the ACC suppresses LTD induction and causes peripheral hypersensitivity. Overexpression of Casp3 restores LTD and reduces peripheral hypersensitivity after nerve injury. We reveal how Casp3 is involved in the maintenance of peripheral hypersensitivity. Our findings suggest that restoration of LTD via Casp3 provides a therapeutic strategy for neuropathic pain management.

Cortical potentiation induced by calcitonin gene-related peptide (CGRP) in the insular cortex of adult mice

Recent studies demonstrate that calcitonin gene-related peptide (CGRP) plays critical roles in migraine. Immunohistochemistry and in situ hybridization studies have shown that CGRP and its receptors are expressed in cortical areas that are critical for pain perception including the anterior cingulate cortex (ACC) and insular cortex (IC). Recent studies reported that CGRP enhanced excitatory transmission in the ACC. However, little is known about the possible effect of CGRP on excitatory transmission in the IC. In the present study, we investigated the role of CGRP on synaptic transmission in the IC slices of adult male mice. Bath application of CGRP produced dose-dependent potentiation of evoked excitatory postsynaptic currents (eEPSCs). This potentiation was NMDA receptor (NMDAR) independent. After application of CGRP1 receptor antagonist CGRP_8–37 or BIBN 4096, CGRP produced potentiation was significantly reduced. Paired-pulse facilitation was significantly decreased by CGRP, suggesting possible presynaptic mechanisms. Consistently, bath application of CGRP significantly increased the frequency of spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs). By contrast, amplitudes of sEPSCs and mEPSCs were not significantly affected. Finally, adenylyl cyclase subtype 1 (AC1) and protein kinase A (PKA) are critical for CGRP-produced potentiation, since both selective AC1 inhibitor NB001 and the PKA inhibitor KT5720 completely blocked the potentiation. Our results provide direct evidence that CGRP contributes to synaptic potentiation in the IC, and the AC1 inhibitor NB001 may be beneficial for the treatment of migraine in the future.

Ethanol Modulates Glutamatergic Transmission and NMDAR-Mediated Synaptic Plasticity in the Agranular Insular Cortex

The agranular insular cortex (AIC) has recently been investigated by the alcohol field because of its connectivity to and modulatory control over limbic and brainstem regions implicated in alcohol use disorder (AUD), and because it has shown involvement in animal models of alcohol drinking. Despite evidence of AIC involvement in AUD, there has not yet been an examination of whether ethanol modulates glutamatergic and γ-amino-butyric acid (GABA)ergic synaptic transmission and plasticity in the AIC. Characterizing how the synaptic transmission and plasticity states of AIC cortical processing neurons are modulated by acute ethanol will likely reveal the molecular targets by which chronic ethanol alters AIC function as alcohol drinking transitions from controlled to problematic. Therefore, we collected brain slices from ethanol-naïve adult male mice, obtained whole-cell recording configuration in layer 2/3 AIC pyramidal neurons, and bath-applied ethanol at pharmacologically relevant concentrations during electrophysiological assays of glutamatergic and GABAergic synaptic transmission and plasticity. We found that ethanol inhibited electrically evoked N-methyl-D-aspartate receptor (NMDAR)-mediated excitatory post-synaptic currents (EPSCs) in a concentration-related fashion, and had little effect on evoked α-amino-3-hydrox-5-methylisoxazole-4-propionic acid-type receptor (AMPAR)-mediated EPSCs. Ethanol had no effect on spontaneous excitatory post-synaptic currents (sEPSCs) or inhibitory GABA_AR-mediated post-synaptic currents (sIPSCs). We found that synaptic conditioning (low-frequency stimulation for 15 min at 1 Hz) induced a form of long-term depression (LTD) of evoked AMPAR-mediated EPSCs. The ability to induce LTD was inhibited by a non-selective NMDAR antagonist (DL-2-amino-5-phosphonovaleric acid), and also by acute, intoxicating concentrations of ethanol. Taken together these data suggest that the glutamate, but not GABA system in the AIC is uniquely sensitive to ethanol, and that in particular NMDAR-mediated processes in the AIC may be disrupted by pharmacologically relevant concentrations of ethanol.

Loss of Synaptic Tagging in the Anterior Cingulate Cortex after Tail Amputation in Adult Mice

Anterior cingulate cortex (ACC) is known to play important roles in key brain functions such as pain perception, cognition, and emotion. Different forms of homosynaptic plasticity such as long-term potentiation (LTP) and long-term depression have been studied in ACC synapses. However, heterosynaptic plasticity such as synaptic tagging has not been reported. Here, we demonstrate synaptic tagging in the ACC of adult male mice by using a 64-channel multielectrode array recording system. Weak theta burst stimulation (TBS), normally inducing early-phase LTP or No-LTP in most of the activated channels, produced late phase-LTP (L-LTP) in a majority of channels when a strong TBS was applied earlier to a separate input within a certain time window. Similar to hippocampus, synaptic tagging in the ACC depends on the synthesis of new proteins. Tail amputation-induced peripheral injury caused a loss of this heterosynaptic L-LTP and occluded strong TBS-evoked L-LTP as well. Together, we provide the first report of the synaptic tagging-like phenomenon in the ACC of adult mice, and the loss of synaptic tagging to amputation may contribute to injury-related cognitive changes and phantom limb sensation and pain.SIGNIFICANCE STATEMENT ACC is an important cortical region involved in many brain functions. Previous studies have dissected the molecular mechanism of multiple types of homosynaptic plasticity of ACC synapses. Here, we report a novel form of heterosynaptic plasticity occurring in the ACC. This newly identified, protein synthesis-dependent neocortical synaptic tagging is sensitive to peripheral tail amputation injury and may provide basic mechanisms for synaptic pathophysiology of phantom pain and related cognitive changes.

Characterization of short- and long-term mechanical sensitisation following surgical tail amputation in pigs

Commercial pigs are frequently exposed to tail mutilations in the form of preventive husbandry procedures (tail docking) or as a result of abnormal behaviour (tail biting). Although tissue and nerve injuries are well-described causes of pain hypersensitivity in humans and in rodent animal models, there is no information on the changes in local pain sensitivity induced by tail injuries in pigs. To determine the temporal profile of sensitisation, pigs were exposed to surgical tail resections and mechanical nociceptive thresholds (MNT) were measured in the acute (one week post-operatively) and in the long-term (either eight or sixteen weeks post-surgery) phase of recovery. The influence of the degree of amputation on MNTs was also evaluated by comparing three different tail-resection treatments (intact, ‘short tail’, ‘long tail’). A significant reduction in MNTs one week following surgery suggests the occurrence of acute sensitisation. Long-term hypersensitivity was also observed in tail-resected pigs at either two or four months following surgery. Tail amputation in pigs appears to evoke acute and sustained changes in peripheral mechanical sensitivity, which resemble features of neuropathic pain reported in humans and other species and provides new information on implications for the welfare of animals subjected to this type of injury.

Metabotropic Glutamate Receptor Dependent Cortical Plasticity in Chronic Pain

Many cortical areas play crucial roles in higher order brain functions such as pain and emotion-processing, decision-making, and cognition. Among them, anterior cingulate cortex (ACC) and insular cortex (IC) are two key areas. Glutamate mediates major excitatory transmission during long-term plasticity in both physiological and pathological conditions. Specifically related to nociceptive or pain behaviors, metabotropic glutamate subtype receptors (mGluRs) have been involved in different types of synaptic modulation and plasticity from periphery to the spinal cord. However, less is known about their functional roles in plasticity related to pain and its related behaviors within cortical regions. In this review, we first summarized previous studies of synaptic plasticity in both the ACC and IC, and discussed how mGluRs may be involved in both cortical long-term potentiation (LTP) and long-term depression (LTD)-especially in LTD. The activation of mGluRs contributes to the induction of LTD in both ACC and IC areas. The loss of LTD caused by peripheral amputation or nerve injury can be rescued by priming ACC or IC with activations of mGluR1 receptors. We also discussed the potential functional roles of mGluRs for pain-related behaviors. We propose that targeting mGluRs in the cortical areas including the ACC and IC may provide a new therapeutic strategy for the treatment of chronic pain, phantom pain or anxiety.

Neonatal Maternal Deprivation Enhances Presynaptic P2X7 Receptor Transmission in Insular Cortex in an Adult Rat Model of Visceral Hypersensitivity

AIMS

Insular cortex (IC) is involved in processing the information of pain. The aim of this study was to investigate roles and mechanisms of P2X7 receptors (P2X7Rs) in IC in development of visceral hypersensitivity of adult rats with neonatal maternal deprivation (NMD).

METHODS

Visceral hypersensitivity was quantified by abdominal withdrawal reflex threshold to colorectal distension (CRD). Expression of P2X7Rs was determined by qPCR and Western blot. Synaptic transmission in IC was recorded by patch-clamp recording.

RESULTS

The expression of P2X7Rs and glutamatergic neurotransmission in IC was significantly increased in NMD rats when compared with age-matched controls. Application of BzATP (P2X7R agonist) enhanced the frequency of spontaneous excitatory postsynaptic currents (sEPSC) and miniature excitatory postsynaptic currents (mEPSC) in IC slices of control rats. Application of BBG (P2X7R antagonist) suppressed the frequencies of sEPSC and mEPSC in IC slices of NMD rats. Microinjection of BzATP into right IC significantly decreased CRD threshold in control rats while microinjection of BBG or A438079 into right IC greatly increased CRD threshold in NMD rats.

CONCLUSION

Data suggested that the enhanced activities of P2X7Rs in IC, likely through a presynaptic mechanism, contributed to visceral hypersensitivity of adult rats with NMD.

Metabotropic glutamate receptor dependent long-term depression in the cortex

Metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD), a type of synaptic plasticity, is characterized by a reduction in the synaptic response, mainly at the excitatory synapses of the neurons. The hippocampus and the cerebellum have been the most extensively studied regions in mGluR-dependent LTD, and Group 1 mGluR has been reported to be mainly involved in this synaptic LTD at excitatory synapses. However, mGluR-dependent LTD in other brain regions may be involved in the specific behaviors or diseases. In this paper, we focus on five cortical regions and review the literature that implicates their contribution to the pathogenesis of several behaviors and specific conditions associated with mGluR-dependent LTD.

Contribution of synaptic plasticity in the insular cortex to chronic pain

Animal and human studies have consistently demonstrated that cortical regions are important for pain perception and pain-related emotional changes. Studies of the anterior cingulate cortex (ACC) have shown that adult cortical synapses can be modified after peripheral injuries, and long-term changes at synaptic level may contribute to long-lasting suffering in patients. It also explains why chronic pain is resistant to conventional analgesics that act by inhibiting synaptic transmission. Insular cortex (IC), another critical cortical area, is found to be highly plastic and can undergo long-term potentiation (LTP) after injury. Inhibiting IC LTP reduces behavioral sensitization caused by injury. LTP of glutamatergic transmission in pain related cortical areas serves as a key mechanism for chronic pain.

Acid-sensing ion channel 1a contributes to hippocampal LTP inducibility through multiple mechanisms

The exact roles of acid-sensing ion channels (ASICs) in synaptic plasticity remain elusive. Here, we address the contribution of ASIC1a to five forms of synaptic plasticity in the mouse hippocampus using an in vitro multi-electrode array recording system. We found that genetic deletion or pharmacological blockade of ASIC1a greatly reduced, but did not fully abolish, the probability of long-term potentiation (LTP) induction by either single or repeated high frequency stimulation or theta burst stimulation in the CA1 region. However, these treatments did not affect hippocampal long-term depression induced by low frequency electrical stimulation or (RS)-3,5-dihydroxyphenylglycine. We also show that ASIC1a exerts its action in hippocampal LTP through multiple mechanisms that include but are not limited to augmentation of NMDA receptor function. Taken together, these results reveal new insights into the role of ASIC1a in hippocampal synaptic plasticity and the underlying mechanisms. This unbiased study also demonstrates a novel and objective way to assay synaptic plasticity mechanisms in the brain.

Minocycline does not affect long-term potentiation in the anterior cingulate cortex of normal adult mice

It has been reported that activated microglia plays important roles in chronic pain-related sensory signaling at the spinal cord dorsal horn. Less is known about the possible contribution of microglia to cortical plasticity that has been found to be important for chronic pain. In the present study, we used a 64-channel multi-electrode array recording system to investigate the role of microglia in cortical plasticity of the anterior cingulate cortex (ACC) in normal adult mice. We found that bath application of minocycline, an inhibitor of microglial activation, had no effect on postsynaptic LTP (post-LTP) induced by theta burst stimulation in the ACC. Furthermore, presynaptic LTP (pre-LTP) induced by the combination of low-frequency stimulation with a GluK1-containing kainate receptor agonist was also not affected. The spatial distribution of post-LTP or pre-LTP among the cingulate network is also unaltered by minocycline. Our results suggest that minocycline does not affect cingulate plasticity and neurons are the major player in pain-related cortical plasticity.

GluA1 phosphorylation contributes to postsynaptic amplification of neuropathic pain in the insular cortex

Long-term potentiation of glutamatergic transmission has been observed after physiological learning or pathological injuries in different brain regions, including the spinal cord, hippocampus, amygdala, and cortices. The insular cortex is a key cortical region that plays important roles in aversive learning and neuropathic pain. However, little is known about whether excitatory transmission in the insular cortex undergoes plastic changes after peripheral nerve injury. Here, we found that peripheral nerve ligation triggered the enhancement of AMPA receptor (AMPAR)-mediated excitatory synaptic transmission in the insular cortex. The synaptic GluA1 subunit of AMPAR, but not the GluA2/3 subunit, was increased after nerve ligation. Genetic knock-in mice lacking phosphorylation of the Ser845 site, but not that of the Ser831 site, blocked the enhancement of the synaptic GluA1 subunit, indicating that GluA1 phosphorylation at the Ser845 site by protein kinase A (PKA) was critical for this upregulation after nerve injury. Furthermore, A-kinase anchoring protein 79/150 (AKAP79/150) and PKA were translocated to the synapses after nerve injury. Genetic deletion of adenylyl cyclase subtype 1 (AC1) prevented the translocation of AKAP79/150 and PKA, as well as the upregulation of synaptic GluA1-containing AMPARs. Pharmacological inhibition of calcium-permeable AMPAR function in the insular cortex reduced behavioral sensitization caused by nerve injury. Our results suggest that the expression of AMPARs is enhanced in the insular cortex after nerve injury by a pathway involving AC1, AKAP79/150, and PKA, and such enhancement may at least in part contribute to behavioral sensitization together with other cortical regions, such as the anterior cingulate and the prefrontal cortices.

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.

No requirement of TRPV1 in long-term potentiation or long-term depression in the anterior cingulate cortex

One major interest in the study of transient receptor potential vanilloid type 1 (TRPV1) in sensory system is that it may serve as a drug target for treating chronic pain. While the roles of TRPV1 in peripheral nociception and sensitization have been well documented, less is known about its contribution to pain-related cortical plasticity. Here, we used 64 multi-electrode array recording to examine the potential role of TRPV1 in two major forms of synaptic plasticity, long-term potentiation (LTP) and long-term depression (LTD), in the anterior cingulate cortex (ACC). We found that pharmacological blockade of TRPV1 with either [(E)-3-(4-t-Butylphenyl)-N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)acrylamide] (AMG9810, 10 μM) or N-(3-methoxyphenyl)-4-chlorocinnamide (SB366791, 20 μM) failed to affect LTP induced by strong theta burst stimulation in the ACC of adult mice. Similarly, neither AMG9810 nor SB366791 blocked the cingulate LTD induced by low-frequency stimulation. Analysis of the results from different layers of the ACC obtained the same conclusions. Spatial distribution of LTP or LTD-showing channels among the ACC network was also unaltered by the TRPV1 antagonists. Since cortical LTP and LTD in the ACC play critical roles in chronic pain triggered by inflammation or nerve injury, our findings suggest that TRPV1 may not be a viable target for treating chronic pain, especially at the cortical level.