Oxytocin in the anterior cingulate cortex attenuates neuropathic pain and emotional anxiety by inhibiting presynaptic long-term potentiation

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'.

Potential role of oxytocin in the regulation of memories and treatment of memory disorders

Oxytocin (OXT) is an "affiliative" hormone or neurohormone or neuropeptide consists of nine amino acids, synthesized in magnocellular neurons of paraventricular (PVN) and supraoptic nuclei (SON) of hypothalamus. OXT receptors are widely distributed in various region of brain and OXT has been shown to regulate various social and nonsocial behavior. Hippocampus is the main region which regulates the learning and memory. Hippocampus particularly regulates the acquisition of new memories and retention of acquired memories. OXT has been shown to regulate the synaptic plasticity, neurogenesis, and consolidation of memories. Further, findings from both preclinical and clinical studies have suggested that the OXT treatment improves performance in memory related task. Various trials have suggested the positive impact of intranasal OXT in the dementia patients. However, these studies are limited in number. In the present study authors have highlighted the role of OXT in the formation and retrieval of memories. Further, the study demonstrated the outcome of OXT treatment in various memory and related disorders.

Neuropeptides affecting social behavior in mammals: Oxytocin

Oxytocin (OXT), a neuropeptide consisting of only nine amino acids, is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Although OXT is best known for its role in lactation and parturition, recent research has shown that it also has a significant impact on social behaviors in mammals. However, a comprehensive review of this topic is still lacking. In this paper, we systematically reviewed the effects of OXT on social behavior in mammals. These effects of OXT from the perspective of five key behavioral dimensions were summarized: parental behavior, anxiety, aggression, attachment, and empathy. To date, researchers have agreed that OXT plays a positive regulatory role in a wide range of social behaviors, but there have been controversially reported results. In this review, we have provided a detailed panorama of the role of OXT in social behavior and, for the first time, delved into the underlying regulatory mechanisms, which may help better understand the multifaceted role of OXT. Levels of OXT in previous human studies were also summarized to provide insights for diagnosis of mental disorders.

Re-wiring of the bonded brain: Gene expression among pair bonded female prairie voles changes as they transition to motherhood

Motherhood is a costly life-history transition accompanied by behavioral and neural plasticity necessary for offspring care. Motherhood in the monogamous prairie vole is associated with decreased pair bond strength, suggesting a trade-off between parental investment and pair bond maintenance. Neural mechanisms governing pair bonds and maternal bonds overlap, creating possible competition between the two. We measured mRNA expression of genes encoding receptors for oxytocin (oxtr), dopamine (d1r and d2r), mu-opioids (oprm1a), and kappa-opioids (oprk1a) within three brain areas processing salience of sociosensory cues (anterior cingulate cortex; ACC), pair bonding (nucleus accumbens; NAc), and maternal care (medial preoptic area; MPOA). We compared gene expression differences between pair bonded prairie voles that were never pregnant, pregnant (~day 16 of pregnancy), and recent mothers (day 3 of lactation). We found greater gene expression in the NAc (oxtr, d2r, oprm1a, and oprk1a) and MPOA (oxtr, d1r, d2r, oprm1a, and oprk1a) following the transition to motherhood. Expression for all five genes in the ACC was greatest for females that had been bonded for longer. Gene expression within each region was highly correlated, indicating that oxytocin, dopamine, and opioids comprise a complimentary gene network for social signaling. ACC-NAc gene expression correlations indicated that being a mother (oxtr and d1r) or maintaining long-term pair bonds (oprm1a) relies on the coordination of different signaling systems within the same circuit. Our study suggests the maternal brain undergoes changes that prepare females to face the trade-off associated with increased emotional investment in offspring, while also maintaining a pair bond.

Effects of paternal deprivation on empathetic behavior and the involvement of oxytocin receptors in the anterior cingulate cortex

Paternal deprivation (PD) impairs social cognition and sociality and increases levels of anxiety-like behavior. However, whether PD affects the levels of empathy in offspring and its underlying mechanisms remain unknown. The present study found that PD increased anxiety-like behavior in mandarin voles (Microtus mandarinus), impaired sociality, reduced the ability of emotional contagion, and the level of consolation behavior. Meanwhile, PD reduced OT neurons in the paraventricular nucleus (PVN) in both male and female mandarin voles. PD decreased the level of OT receptor (OTR) mRNA in the anterior cingulate cortex (ACC) of male and female mandarin voles. Besides, OTR overexpression in the ACC reversed the PD-induced changes in anxiety-like behavior, social preference, emotional contagion, and consolation behavior. Interference of OTR expression in the ACC increased levels of anxiety-like behaviors, while it reduced levels of sociality, emotional contagion, and consolation. These results revealed that the OTR in the ACC is involved in the effects of PD on empathetic behaviors, and provide mechanistic insight into how social experiences affect empathetic behaviors.

Electroacupuncture attenuates neuropathic pain via suppressing BIP-IRE-1α-mediated endoplasmic reticulum stress in the anterior cingulate cortex

Studies have suggested that endoplasmic reticulum stress (ERS) is involved in neurological dysfunction and that electroacupuncture (EA) attenuates neuropathic pain (NP) via undefined pathways. However, the role of ERS in the anterior cingulate cortex (ACC) in NP and the effect of EA on ERS in the ACC have not yet been investigated. In this study, an NP model was established by chronic constriction injury (CCI) of the left sciatic nerve in rats, and mechanical and cold tests were used to evaluate behavioral hyperalgesia. The protein expression and distribution were evaluated using western blotting and immunofluorescence. The results showed that glucose-regulated protein 78 (BIP) and inositol-requiring enzyme 1α (IRE-1α) were co-localized in neurons in the ACC. After CCI, BIP, IRE-1α, and phosphorylation of IRE-1α were upregulated in the ACC. Intra-ACC administration of 4-PBA and Kira-6 attenuated pain hypersensitivity and downregulated phosphorylation of IRE-1α, while intraperitoneal injection of 4-PBA attenuated hyperalgesia and inhibited the activation of P38 and JNK in ACC. In contrast, ERS activation by intraperitoneal injection of tunicamycin induced behavioral hyperalgesia in naive rats. Furthermore, EA attenuated pain hypersensitivity and inhibited the CCI-induced overexpression of BIP and pIRE-1α. Taken together, these results demonstrate that EA attenuates NP by suppressing BIP- and IRE-1α-mediated ERS in the ACC. Our study presents novel evidence that ERS in the ACC is implicated in the development of NP and provides insights into the molecular mechanisms involved in the analgesic effect of EA.

Oxytocin attenuates neuroinflammation-induced anxiety through restoration of excitation and inhibition balance in the anterior cingulate cortex in mice

BACKGROUND

Accumulative evidence suggested that the oxytocin system plays a role in socio-emotional disorders, although its role in neuroinflammation-induced anxiety remains unclear.

METHOD

In the present study, anxiety-like behavior was induced in cohorts of animals through repeated lipopolysaccharide (LPS, 0.5 mg/kg, daily, Escherichia coli O55:B5) i.p. injections for seven consecutive days. These different cohorts were subsequently used for anxiety-like behavior assessment with open field test, elevated plus maze, and novelty-suppressed feeding test or for electrophysiology (EEG) recordings of miniature excitatory postsynaptic currents (mEPSCs), miniature inhibitory postsynaptic currents (mIPSCs), or local field potential (LFP) in vivo or ex vivo settings. Samples of the anterior cingulate cortex (ACC) from some cohorts were harvested to conduct immunostaining or western blotting analysis of oxytocin, oxytocin receptor, CamkII, GABA, vGAT, vGLUT2, and c-fos. The dendritic spine density was assessed by Golgi-Cox staining.

RESULTS

Repeated LPS injections induced anxiety-like behavior with concurrent decreases of oxytocin, vGLUT2, mEPSC, dendritic spine, c-fos, membrane excitability, and EEG beta and gamma oscillations, but increased oxytocin receptor and vGAT expressions in the ACC; all these changes were ameliorated by oxytocin intranasal or local brain (via cannula) administration.

CONCLUSION

Taken together, our data suggested that oxytocin system may be a therapeutic target for developing treatment to tackle neuroinflammation-induced anxiety.

Elevated circulating soluble interleukin-2 receptor (sCD25) level is associated with prefrontal excitatory-inhibitory imbalance in individuals with chronic pain: A proton MRS study

Aberrant neuronal excitability in the anterior cingulate cortex (ACC) is implicated in cognitive and affective pain processing. Such excitability may be amplified by activated circulating immune cells, including T lymphocytes, that interact with the central nervous system. Here, we conducted a study of individuals with chronic pain using magnetic resonance spectroscopy (MRS) to investigate the clinical evidence for the interaction between peripheral immune activation and prefrontal excitatory-inhibitory imbalance. In thirty individuals with chronic musculoskeletal pain, we assessed markers of peripheral immune activation, including soluble interleukin-2 receptor alpha chain (sCD25) levels, as well as brain metabolites, including Glx (glutamate + glutamine) to GABA+ (γ-aminobutyric acid + macromolecules/homocarnosine) ratio in the ACC. We found that the circulating level of sCD25 was associated with prefrontal Glx/GABA+. Greater prefrontal Glx/GABA+ was associated with higher pain catastrophizing, evaluative pain ratings, and anxiodepressive symptoms. Further, the interaction effect of sCD25 and prefrontal Glx/GABA+ on pain catastrophizing was significant, indicating the joint association of these two markers with pain catastrophizing. Our results provide the first evidence suggesting that peripheral T cellular activation, as reflected by elevated circulating sCD25 levels, may be linked to prefrontal excitatory-inhibitory imbalance in individuals with chronic pain. The interaction between these two systems may play a role as a potential mechanism underlying pain catastrophizing. Further prospective and treatment studies are needed to elucidate the specific role of the immune and brain interaction in pain catastrophizing.

The psychophysiology of music-based interventions and the experience of pain

In modern times there is increasing acceptance that music-based interventions are useful aids in the clinical treatment of a range of neurological and psychiatric conditions, including helping to reduce the perception of pain. Indeed, the belief that music, whether listening or performing, can alter human pain experiences has a long history, dating back to the ancient Greeks, and its potential healing properties have long been appreciated by indigenous cultures around the world. The subjective experience of acute or chronic pain is complex, influenced by many intersecting physiological and psychological factors, and it is therefore to be expected that the impact of music therapy on the pain experience may vary from one situation to another, and from one person to another. Where pain persists and becomes chronic, aberrant central processing is a key feature associated with the ongoing pain experience. Nonetheless, beneficial effects of exposure to music on pain relief have been reported across a wide range of acute and chronic conditions, and it has been shown to be effective in neonates, children and adults. In this comprehensive review we examine the various neurochemical, physiological and psychological factors that underpin the impact of music on the pain experience, factors that potentially operate at many levels - the periphery, spinal cord, brainstem, limbic system and multiple areas of cerebral cortex. We discuss the extent to which these factors, individually or in combination, influence how music affects both the quality and intensity of pain, noting that there remains controversy about the respective roles that diverse central and peripheral processes play in this experience. Better understanding of the mechanisms that underlie music's impact on pain perception together with insights into central processing of pain should aid in developing more effective synergistic approaches when music therapy is combined with clinical treatments. The ubiquitous nature of music also facilitates application from the therapeutic environment into daily life, for ongoing individual and social benefit.

Electroacupuncture Exerts Analgesic Effects by Restoring Hyperactivity via Cannabinoid Type 1 Receptors in the Anterior Cingulate Cortex in Chronic Inflammatory Pain

As one of the commonly used therapies for pain-related diseases in clinical practice, electroacupuncture (EA) has been proven to be effective. In chronic pain, neurons in the anterior cingulate cortex (ACC) have been reported to be hyperactive, while the mechanism by which cannabinoid type 1 receptors (CB1Rs) in the ACC are involved in EA-mediated analgesic mechanisms remains to be elucidated. In this study, we investigated the potential central mechanism of EA analgesia. A combination of techniques was used to detect the expression and function of CB1R, including quantitative real-time PCR (q-PCR), western blot (WB), immunofluorescence (IF), enzyme-linked immunosorbent assay (ELISA), and in vivo multichannel optical fibre recording, and neuronal activity was examined by in vivo two-photon imaging and in vivo electrophysiological recording. We found that the hyperactivity of pyramidal neurons in the ACC during chronic inflammatory pain is associated with impairment of the endocannabinoid system. EA at the Zusanli acupoint (ST36) can reduce the hyperactivity of pyramidal neurons and exert analgesic effects by increasing the endocannabinoid ligands anandamide (AEA), 2-arachidonoylglycerol (2-AG) and CB1R. More importantly, CB1R in the ACC is one of the necessary conditions for the EA-mediated analgesia effect, which may be related to the negative regulation of the N-methyl-D-aspartate receptor (NMDAR) by the activation of CB1R downregulating NR1 subunits of NMDAR (NR1) via histidine triad nucleotide-binding protein 1 (HINT1). Our study suggested that the endocannabinoid system in the ACC plays an important role in acupuncture analgesia and provides evidence for a central mechanism of EA-mediated analgesia.

Integrated analysis of transcriptional changes in major depressive disorder: Insights from blood and anterior cingulate cortex

Background

Major depressive disorder (MDD) was involved in widely transcriptional changes in central and peripheral tissues. While, previous studies focused on single tissues, making it difficult to represent systemic molecular changes throughout the body. Thus, there is an urgent need to explore the central and peripheral biomarkers with intrinsic correlation.

Methods

We systematically retrieved gene expression profiles of blood and anterior cingulate cortex (ACC). 3 blood datatsets (84 MDD and 88 controls) and 6 ACC datasets (100 MDD and 100 controls) were obtained. Differential expression analysis, RobustRankAggreg (RRA) analysis, functional enrichment analysis, immune associated analysis and protein-protein interaction networks (PPI) were integrated. Furthermore, the key genes were validated in an independent ACC dataset (12 MDD and 15 controls) and a cohort with 120 MDD and 117 controls.

Results

Differential expression analysis identified 2211 and 2021 differential expressed genes (DEGs) in blood and ACC, respectively. RRA identified 45 and 25 robust DEGs in blood and ACC based on DEGs, and all of them were closely associated with immune cells. Functional enrichment results showed both the robust DEGs in blood and ACC were enriched in humoral immune response. Furthermore, PPI identified 8 hub DEGs (CD79A, CD79B, CD19, MS4A1, PLP1, CLDN11, MOG, MAG) in blood and ACC. Independent ACC dataset showed the area under the curve (AUC) based on these hub DEGs was 0.77. Meanwhile, these hub DEGs were validated in the serum of MDD patients, and also showed a promising diagnostic power.

Conclusions

The biomarker panel based on hub DEGs yield a promising diagnostic efficacy, and all of these hub DEGs were strongly correlated with immunity. Humoral immune response may be the key link between the brain and blood in MDD, and our results may provide further understanding for MDD.

Propofol Alleviates Anxiety-Like Behaviors Associated with Pain by Inhibiting the Hyperactivity of PVNCRH Neurons via GABAA Receptor β3 Subunits

Pain, a comorbidity of anxiety disorders, causes substantial clinical, social, and economic burdens. Emerging evidence suggests that propofol, the most commonly used general anesthetic, may regulate psychological disorders; however, its role in pain-associated anxiety is not yet described. This study investigates the therapeutic potential of a single dose of propofol (100 mg kg-1) in alleviating pain-associated anxiety and examines the underlying neural mechanisms. In acute and chronic pain models, propofol decreased anxiety-like behaviors in the elevated plus maze (EPM) and open field (OF) tests. Propofol also reduced the serum levels of stress-related hormones including corticosterone, corticotropin-releasing hormone (CRH), and norepinephrine. Fiber photometry recordings indicated that the calcium signaling activity of CRH neurons in the paraventricular nucleus (PVNCRH) is reduced after propofol treatment. Interestingly, artificially activating PVNCRH neurons through chemogenetics interfered with the anxiety-reducing effects of propofol. Electrophysiological recordings indicated that propofol decreases the activity of PVNCRH neurons by increasing spontaneous inhibitory postsynaptic currents (sIPSCs). Further, reducing the levels of γ-aminobutyric acid type A receptor β3 (GABAAβ3) subunits in PVNCRH neurons diminished the anxiety-relieving effects of propofol. In conclusion, this study provides a mechanistic and preclinical rationale to treat pain-associated anxiety-like behaviors using a single dose of propofol.

Disfunction of dorsal raphe nucleus-hippocampus serotonergic-HTR3 transmission results in anxiety phenotype of Neuroplastin 65-deficient mice

Anxiety disorders are the most common psychiatric condition, but the etiology of anxiety disorders remains largely unclear. Our previous studies have shown that neuroplastin 65 deficiency (NP65-/-) mice exhibit abnormal social and mental behaviors and decreased expression of tryptophan hydroxylase 2 (TPH2) protein. However, whether a causal relationship between TPH2 reduction and anxiety disorders exists needs to be determined. In present study, we found that replenishment of TPH2 in dorsal raphe nucleus (DRN) enhanced 5-HT level in the hippocampus and alleviated anxiety-like behaviors. In addition, injection of AAV-NP65 in DRN significantly increased TPH2 expression in DRN and hippocampus, and reduced anxiety-like behaviors. Acute administration of exogenous 5-HT or HTR3 agonist SR57227A in hippocampus mitigated anxiety-like behaviors in NP65-/- mice. Moreover, replenishment of TPH2 in DRN partly repaired the impairment of long-term potentiation (LTP) maintenance in hippocampus of NP65-/- mice. Finally, we found that loss of NP65 lowered transcription factors Lmx1b expression in postnatal stage and replenishment of NP65 in DRN reversed the decrease in Lmx1b expression of NP65-/- mice. Together, our findings reveal that NP65 deficiency induces anxiety phenotype by downregulating DRN-hippocampus serotonergic-HTR3 transmission. These studies provide a novel and insightful view about NP65 function, suggesting an attractive potential target for treatment of anxiety disorders.

Impaired neuronal macroautophagy in the prelimbic cortex contributes to comorbid anxiety-like behaviors in rats with chronic neuropathic pain

A large proportion of patients with chronic pain experience co-morbid anxiety. The medial prefrontal cortex (mPFC) is proposed to underlie this comorbidity, but the molecular and neuronal mechanisms are not fully understood. Here, we reported that impaired neuronal macroautophagy in the prelimbic cortical (PrL) subregion of the mPFC paralleled the occurrence of anxiety-like behaviors in rats with chronic spared nerve injury (SNI). Intriguingly, such macroautophagy impairment was mainly observed in a FOS/c-Fos+ neuronal subpopulation in the PrL. Chemogenetic inactivation of this comorbid anxiety-related neuronal ensemble relieved pain-induced anxiety-like behaviors. Rescuing macroautophagy impairment in this neuronal ensemble relieved chronic pain-associated anxiety and mechanical allodynia and restored synaptic homeostasis at the molecular level. By contrast, artificial disruption of macroautophagy induced early-onset co-morbid anxiety in neuropathic rats, but not general anxiety in normal rats. Taken together, our work identifies causal linkage between PrL neuronal macroautophagy dysfunction and comorbid anxiety in neuropathic pain and provides novel insights into the role of PrL by differentiating its contribution in pain-induced comorbid anxiety from its modulation over general anxiety-like behaviors.Abbreviation: AAV: adeno-associated viruses; ACC: anterior cingulate cortex; ATG5: autophagy related 5; ATG7: autophagy related 7; ATG12: autophagy related 12; CAMK2/CaMKII: calcium/calmodulin-dependent protein kinase II; CNO: clozapine-N-oxide; CQ: chloroquine; DIA: data independent acquisition; DIO: double floxed inverse orf; DLG4/PSD-95: discs large MAGUK scaffold protein 4; Dox: doxycycline; GABA: γ-aminobutyric acid; GFP: green fluorescent protein; GO: gene ontology; Gi: inhibitory guanine nucleotide-binding proteins; HsCHRM4/M4D: human cholinergic receptor muscarinic 4; HsSYN: human synapsin; KEGG: Kyoto encyclopedia of genes and genomes; LAMP1: lysosomal-associated membrane protein 1; LC3-II: PE conjugated microtubule-associated protein 1 light chain3; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; mPFC: medial prefrontal cortex; P2A: 2A self-cleaving peptide; PPI: protein-protein interaction networks; PrL: prelimbic cortex; RBFOX3/NeuN: RNA binding protein, fox-1 homolog (C. elegans) 3; rtTA: reverse tetracycline-transactivator; SDS-PAGE: sodium dodecylsulfate-polyacrylamide gel electrophoresis; SHANK3: SH3 and multiple ankyrin repeat domains 3; SLC1A1/EAAC1: solute carrier family 1 (neuronal/epithelial high affinity glutamate transporter, systemXag), member 1; SNAP23: synaptosomal-associated protein 23; SNI:spared nerve injury; SQSTM1/p62: sequestosome 1; SYT3: synaptotagmin 3; TRE: tetracycline-responsive element; TRE3G: third-generation tetracycline-responsive element.

Chronic Pain-Related Cognitive Deficits: Preclinical Insights into Molecular, Cellular, and Circuit Mechanisms

Cognitive impairment is a common comorbidity of chronic pain, significantly disrupting patients' quality of life. Despite this comorbidity being clinically recognized, the underlying neuropathological mechanisms remain unclear. Recent preclinical studies have focused on the fundamental mechanisms underlying the coexistence of chronic pain and cognitive decline. Pain chronification is accompanied by structural and functional changes in the neural substrate of cognition. Based on the developments in electrophysiology and optogenetics/chemogenetics, we summarized the relevant neural circuits involved in pain-induced cognitive impairment, as well as changes in connectivity and function in brain regions. We then present the cellular and molecular alternations related to pain-induced cognitive impairment in preclinical studies, mainly including modifications in neuronal excitability and structure, synaptic plasticity, glial cells and cytokines, neurotransmitters and other neurochemicals, and the gut-brain axis. Finally, we also discussed the potential treatment strategies and future research directions.

Optogenetic Approach in Trigeminal Neuralgia and Potential Concerns: Preclinical Insights

The integration of optogenetics in the trigeminal pain circuitry broadens and reinforces existing pain investigations. Similar to research on spinal neuropathic pain, the exploration of the underlying determinants of orofacial pain is expanding. Optogenetics facilitates more direct, specific, and subtle investigations of the neuronal circuits involved in orofacial pain. One of the most significant concerns of both dentistry and medicine is trigeminal neuralgia (TN) management due to its substantial impact on a patient's quality of life. Our objective is to gather insights from preclinical studies conducted in TN employing an optogenetic paradigm, thereby extending the prospects for in-depth neurobiological research. This review highlights optogenetic research in trigeminal pain circuitry involving TN. We outline the central and peripheral regions associated with pain-that have been investigated using optogenetics in the trigeminal pain circuitry. The study further reports its scope and limitations as well as its potential for future applications from bench to bedside.

Selective enhancement of fear extinction by inhibiting neuronal adenylyl cyclase 1 (AC1) in aged mice

Adenylyl cyclase 1 (AC1) is a selective subtype of ACs, which is selectively expressed in neurons. The activation of AC1 is activity-dependent, and AC1 plays an important role in cortical excitation that contributes to chronic pain and related emotional disorders. Previous studies have reported that human-used NB001 (hNB001, a selective AC1 inhibitor) produced analgesic effects in different animal models of chronic pain. However, the potential effects of hNB001 on learning and memory have been less investigated. In the present study, we found that hNB001 affected neither the induction nor the expression of trace fear, but selectively enhanced the relearning ability during the extinction in aged mice. By contrast, the same application of hNB001 did not affect recent, remote auditory fear memory, or remote fear extinction in either adult or aged mice. Furthermore, a single or consecutive 30-day oral administration of hNB001 did not affect acute nociceptive response, motor function, or anxiety-like behavior in either adult or aged mice. Our results are consistent with previous findings that inhibition of AC1 did not affect general sensory, emotional, and motor functions in adult mice, and provide strong evidence that inhibiting the activity of AC1 may be beneficial for certain forms of learning and memory in aged mice.

Investigating the brain functional abnormalities underlying pain hypervigilance in chronic neck and shoulder pain: a resting-state fMRI study

PURPOSE

To investigate pain hypervigilance in individuals suffering from chronic neck and shoulder pain (CNSP) and its underlying brain mechanism.

METHODS

The evaluation of pain vigilance was conducted through the utilization of pain vigilance and awareness questionnaires. Voxel-wise regional homogeneity (ReHo) from 60 CNSP patients and 60 healthy controls (HCs) using resting-state fMRI data. Voxel-wise two-sample T-test was conducted to reveal the ReHo variations between CNSP and HC. Correlation analyses were utilized to reveal the connection between brain abnormalities and medical measurements. Furthermore, a mediation analysis was conducted to elucidate the pathway-linking changes in brain function with medical measurements.

RESULTS

Our present study revealed three main findings. Firstly, patients with CSNP demonstrated a heightened vigilance of pain in comparison to healthy adults, a common occurrence among individuals with chronic pain conditions. Secondly, we observed brain abnormalities in various brain regions in CSNP patients, and these alterations were associated with the extent of pain vigilance. Lastly, the pain hypervigilance impact on the severity of pain was found to be controlled by regional neural activity in the anterior cingulate cortex (ACC) in subjects with CSNP.

CONCLUSION

Our findings suggested that long-term repetitive nociceptive input caused by chronic pain further aggravates the pain intensity by impairing the vigilance-related pain processing within the anterior cingulate cortex in CNSP patients.

Exploring Functional Connectivity in Chronic Spinal Cord Injury Patients With Neuropathic Pain Versus Without Neuropathic Pain

The great majority of spinal cord injury (SCI) patients have debilitating chronic pain. Despite decades of research, these pain pathways of neuropathic pain (NP) are unknown. SCI patients have been shown to have abnormal brain pain pathways. We hypothesize that SCI NP patients' pain matrix is altered compared to SCI patients without NP. This study examines the functional connectivity (FC) in SCI patients with moderate-severe chronic NP compared to SCI patients with mild-no NP. These groups were compared to control subjects. The Neuropathic Pain Questionnaire and neurological evaluation based on the International Standard Neurological Classification of SCI were utilized to define the severity and level of injury. Of the 10 SCI patients, 7 (48.6 ± 17.02 years old, 6 male and 1 female) indicated that they had NP and 3 did not have NP (39.33 ± 8.08 years old, 2 male and 1 female). Ten uninjured neurologically intact participants were used as controls (24.8 ± 4.61 years old, 5 male and 5 female). FC metrics were obtained from the comparisons of resting-state functional magnetic resonance imaging among our various groups (controls, SCI with NP, and SCI without NP). For each comparison, a region-of-interest (ROI)-to-ROI connectivity analysis was pursued, encompassing a total of 175 ROIs based on a customized atlas derived from the AAL3 atlas. The analysis accounted for covariates such as age and sex. To correct for multiple comparisons, a strict Bonferroni correction was applied with a significance level of p < 0.05/NROIs. When comparing SCI patients with moderate-to-severe pain to those with mild-to-no pain, specific thalamic nuclei had altered connections. These nuclei included: medial pulvinar; lateral pulvinar; medial geniculate nucleus; lateral geniculate nucleus; and mediodorsal magnocellular nucleus. There was increased FC between the lateral geniculate nucleus and the anteroventral nucleus in NP post-SCI. Our analysis additionally highlights the relationships between the frontal lobe and temporal lobe with pain. This study successfully identifies thalamic neuroplastic changes that occur in patients with SCI who develop NP. It additionally underscores the pain matrix and involvement of the frontal and temporal lobes as well. Our findings complement that the development of NP post-SCI involves cognitive, emotional, and behavioral influences.

Recruitment of cortical silent responses by forskolin in the anterior cingulate cortex of adult mice

Recent studies using different experimental approaches demonstrate that silent synapses may exist in the adult cortex including the sensory cortex and anterior cingulate cortex (ACC). The postsynaptic form of long-term potentiation (LTP) in the ACC recruits some of these silent synapses and the activity of calcium-stimulated adenylyl cyclases (ACs) is required for such recruitment. It is unknown if the chemical activation of ACs may recruit silent synapses. In this study, we found that activation of ACs contributed to synaptic potentiation in the ACC of adult mice. Forskolin, a selective activator of ACs, recruited silent responses in the ACC of adult mice. The recruitment was long-lasting. Interestingly, the effect of forskolin was not universal, some silent synapses did not undergo potentiation or recruitment. These findings suggest that these adult cortical synapses are not homogenous. The application of a selective calcium-permeable AMPA receptor inhibitor 1-naphthyl acetyl spermine (NASPM) reversed the potentiation and the recruitment of silent responses, indicating that the AMPA receptor is required. Our results strongly suggest that the AC-dependent postsynaptic AMPA receptor contributes to the recruitment of silent responses at cortical LTP.

Intranasal oxytocin alleviates comorbid depressive symptoms in neuropathic pain via elevating hippocampal BDNF production in both female and male mice

The comorbidity of pain and depression is frequently observed in patients suffering from chronic pain and depression. However, the comorbid mechanism is not well elucidated and the therapeutic medication is still inadequate. Oxytocin is a neuropeptide synthesized in the hypothalamus. It has been reported to relieve chronic pain and depressive symptoms. However, the analgesic action and mechanisms of oxytocin have mainly been investigated using peripheral or spinal administration. Because of the advantage of intranasal delivery of oxytocin in crossing the blood-brain barrier, we investigated the effect of intranasal application of oxytocin on neuropathic pain and comorbid depressive symptoms in both female and male mice. In female and male mice receiving spared nerve injury (SNI) surgery, intranasal oxytocin (2.4 μg, daily for 28 days) attenuated depression-like behavior, but did not alleviate mechanical hyperalgesia. Intranasal oxytocin not only inhibited the activation of microglia and astrocytes, but also increased the downregulated oxytocin receptor (OTR) expression, reversed the elevated GluN2A, and restored the decreased BDNF expression in the hippocampus. SNI also decreased OTR expression in the spinal cord and increased spinal GluN2A and BDNF. However, intranasal oxytocin treatment did not change the expression levels of OTR, GluN2A, or BDNF in the spinal cord of neuropathic mice. The results suggest that the oxytocin signaling in the hippocampus is involved in the comorbidity of pain and depression, and intranasal oxytocin may have the potential to treat depressive symptoms in neuropathic pain patients.

Activation of the glutamatergic cingulate cortical-cortical connection facilitates pain in adult mice

The brain consists of the left and right cerebral hemispheres and both are connected by callosal projections. Less is known about the basic mechanism of this cortical-cortical connection and its functional importance. Here we investigate the cortical-cortical connection between the bilateral anterior cingulate cortex (ACC) by using the classic electrophysiological and optogenetic approach. We find that there is a direct synaptic projection from one side ACC to the contralateral ACC. Glutamate is the major excitatory transmitter for bilateral ACC connection, including projections to pyramidal cells in superficial (II/III) and deep (V/VI) layers of the ACC. Both AMPA and kainate receptors contribute to synaptic transmission. Repetitive stimulation of the projection also evoked postsynaptic Ca2+ influx in contralateral ACC pyramidal neurons. Behaviorally, light activation of the ACC-ACC connection facilitated behavioral withdrawal responses to mechanical stimuli and noxious heat. In an animal model of neuropathic pain, light inhibitory of ACC-ACC connection reduces both primary and secondary hyperalgesia. Our findings provide strong direct evidence for the excitatory or facilitatory contribution of ACC-ACC connection to pain perception, and this mechanism may provide therapeutic targets for future treatment of chronic pain and related emotional disorders.

A novel endomorphin-2/salmon calcitonin hybrid peptide with enhancing anti-allodynic and anti-anxiety effects

Pain, a worldwide problem with a high incidence and complex pathogenesis, has attracted the attention of pharmaceutical enterprises for the development of safer and more effective drugs. Extensive experimental and clinical evidence has demonstrated the analgesic effects of two endogenous peptides: endomorphin-2 (EM-2) and salmon calcitonin (sCT). However, EM-2 has limitations, such as poor ability to cross the blood-brain barrier (BBB) and little therapeutic effect in chronic pain due to rapid in vivo proteolysis. Herein, we propose the design of a novel hybrid peptide TEM2CT by combining EM-2, sCT16-21, and the cell-penetrating peptide HIV-1 trans-activator protein (TAT) with the aim of enhancing their analgesic effects. TEM2CT treatment attenuated nociceptive behavior in both acute and chronic pain mouse models, exhibiting increased anti-allodynic and anti-anxiety effects compared to sCT treatment. Furthermore, TEM2CT also regulated the excitability of pyramidal neurons in the anterior cingulate cortex (ACC) in spared nerve injury (SNI) model mice. The improved efficacy of this hybrid peptide provides a promising strategy for developing analgesic drugs.

Distinct ACC Neural Mechanisms Underlie Authentic and Transmitted Anxiety Induced by Maternal Separation in Mice

It is known that humans and rodents are capable of transmitting stress to their naive partners via social interaction. However, a comprehensive understanding of transmitted stress, which may differ from authentic stress, thus revealing unique neural mechanisms of social interaction resulting from transmitted stress and the associated anxiety, is missing. We used, in the present study, maternal separation (MS) as a stress model to investigate whether MS causes abnormal behavior in adolescence. A key concern in the analysis of stress transmission is whether the littermates of MS mice who only witness MS stress ("Partners") exhibit behavioral abnormalities similar to those of MS mice themselves. Of special interest is the establishment of the neural mechanisms underlying transmitted stress and authentic stress. The results show that Partners, similar to MS mice, exhibit anxiety-like behavior and hyperalgesia after witnessing littermates being subjected to early-life repetitive MS. Electrophysiological analysis revealed that mice subjected to MS demonstrate a reduction in both the excitatory and inhibitory synaptic activities of parvalbumin interneurons (PVINs) in the anterior cingulate cortex (ACC). However, Partners differed from MS mice in showing an increase in the number and excitability of GABAergic PVINs in the ACC and in the ability of chemogenetic PVIN inactivation to eliminate abnormal behavior. Furthermore, the social transfer of anxiety-like behavior required intact olfactory, but not visual, perception. This study suggests a functional involvement of ACC PVINs in mediating the distinct neural basis of transmitted anxiety.SIGNIFICANCE STATEMENT The anterior cingulate cortex (ACC) is a critical brain area in physical and social pain and contributes to the exhibition of abnormal behavior. ACC glutamatergic neurons have been shown to encode transmitted stress, but it remains unclear whether inhibitory ACC neurons also play a role. We evaluate, in this study, ACC neuronal, synaptic and network activities and uncover a critical role of parvalbumin interneurons (PVINs) in the expression of transmitted stress in adolescent mice who had witnessed MS of littermates in infancy. Furthermore, inactivation of ACC PVINs blocks transmitted stress. The results suggest that emotional contagion has a severe effect on brain function, and identify a potential target for the treatment of transmitted anxiety.

Therapeutic uses of oxytocin in stress-related neuropsychiatric disorders

Oxytocin (OXT), produced and secreted in the paraventricular nucleus and supraoptic nucleus of magnocellular and parvocellular neurons. The diverse presence and activity of oxytocin suggests a potential for this neuropeptide in the pathogenesis and treatment of stress-related neuropsychiatric disorders (anxiety, depression and post-traumatic stress disorder (PTSD)). For a more comprehensive understanding of the mechanism of OXT's anti-stress action, the signaling cascade of OXT binding to targeting stress were summarized. Then the advance of OXT treatment in depression, anxiety, PTSD and the major projection region of OXT neuron were discussed. Further, the efficacy of endogenous and exogenous OXT in stress responses were highlighted in this review. To augment the level of OXT in stress-related neuropsychiatric disorders, current biological strategies were summarized to shed a light on the treatment of stress-induced psychiatric disorders. We also conclude some of the major puzzles in the therapeutic uses of OXT in stress-related neuropsychiatric disorders. Although some questions remain to be resolved, OXT has an enormous potential therapeutic use as a hormone that regulates stress responses.

Neuroprotective effects of oxytocin against ischemic stroke in rats by blocking glutamate release and CREB-mediated DNA hypermethylation

Glutamate plays a crucial role in cognitive impairments after ischemic stroke. There is a scarcity of information about how glutamate-induced activation of cAMP-response element binding (CREB) signaling pathway regulates both the negative and positive regulators of synaptic plasticity. Recent studies have demonstrated the involvement of prominent epigenetic repressors, such as MeCP2 and DNMTs, in stroke. Neuroprotective effects of oxytocin against ischemia have been previously reported, while the underlying mechanism is still elusive. In this research, the possible role of CREB-mediated DNA hypermethylation and the potential mechanism of oxytocin in a rat model of permanent middle cerebral artery occlusion (pMCAO) were assessed. Adult male Sprague-Dawley rats were pretreated with intraperitoneal injection of oxytocin at the onset of pMCAO. The effects of oxytocin on spines and the expression levels of synaptic genes were determined. The regulatory effects of oxytocin on glutamate level, N-methyl-D-aspartate receptors (NMDARs), its downstream CREB pathway, and global or gene-specific DNA methylation status were evaluated by immunofluorescence, co-immunoprecipitation, and chromatin immunoprecipitation, respectively. We found that CREB could act as a common transcription factor for MeCP2 and DNMT3B after ischemic stroke. Oxytocin dose-dependently deactivated NR2B-related CaM-CREB pathway and inhibited DNA hypermethylation at the CpG islands of Ngf gene in pMCAO-operated rats. Moreover, oxytocin prevented pMCAO-induced reduction in the number of spines and neural cells. DNA hypermethylation in Ngf gene contributed to the cognitive deficits post-stroke. The neuroprotective effects of oxytocin against ischemia could be attributed to inhibiting glutamate release, providing additional evidence on the mechanism of oxytocin against ischemic stroke.

Associations between childhood ethnoracial minority density, cortical thickness, and social engagement among minority youth at clinical high-risk for psychosis

An ethnoracial minority density (EMD) effect in studies of psychotic spectrum disorders has been observed, whereby the risk of psychosis in ethnoracial minority group individuals is inversely related to the proportion of minorities in their area of residence. The authors investigated the relationships among area-level EMD during childhood, cortical thickness (CT), and social engagement (SE) in clinical high risk for psychosis (CHR-P) youth. Data were collected as part of the North American Prodrome Longitudinal Study. Participants included 244 ethnoracial minoritized (predominantly Hispanic, Asian and Black) CHR-P youth and ethnoracial minoritized healthy controls. Among youth at CHR-P (n = 164), lower levels of EMD during childhood were associated with reduced CT in the right fusiform gyrus (adjusted β = 0.54; 95% CI 0.17 to 0.91) and right insula (adjusted β = 0.40; 95% CI 0.05 to 0.74). The associations between EMD and CT were significantly moderated by SE: among youth with lower SE (SE at or below the median, n = 122), lower levels of EMD were significantly associated with reduced right fusiform gyrus CT (adjusted β = 0.72; 95% CI 0.29 to 1.14) and reduced right insula CT (adjusted β = 0.57; 95% CI 0.18 to 0.97). However, among those with greater SE (n = 42), the associations between EMD and right insula and fusiform gyrus CT were not significant. We found evidence that lower levels of ethnic density during childhood were associated with reduced cortical thickness in regional brain regions, but this association may be buffered by greater levels of social engagement.

Paraventricular nucleus-central amygdala oxytocinergic projection modulates pain-related anxiety-like behaviors in mice

AIMS

Anxiety disorders associated with pain are a common health problem. However, the underlying mechanisms remain poorly understood. We aimed to investigate the role of paraventricular nucleus (PVN)-central nucleus of the amygdala (CeA) oxytocinergic projections in anxiety-like behaviors induced by inflammatory pain.

METHODS

After inflammatory pain induction by complete Freund's adjuvant (CFA), mice underwent elevated plus maze, light-dark transition test, and marble burying test to examine the anxiety-like behaviors. Chemogenetic, optogenetic, and fiber photometry recordings were used to modulate and record the activity of the oxytocinergic projections of the PVN-CeA.

RESULTS

The key results are as follows: inflammatory pain-induced anxiety-like behaviors in mice accompanied by decreased activity of PVN oxytocin neurons. Chemogenetic activation of PVN oxytocin neurons prevented pain-related anxiety-like behaviors, whereas inhibition of PVN oxytocin neurons induced anxiety-like behaviors in naïve mice. PVN oxytocin neurons projected directly to the CeA, and microinjection of oxytocin into the CeA blocked anxiety-like behaviors. Inflammatory pain also decreased the activity of CeA neurons, and optogenetic activation of PVNoxytocin -CeA circuit prevented anxiety-like behavior in response to inflammatory pain.

CONCLUSION

The results of our study suggest that oxytocin has anti-anxiety effects and provide novel insights into the role of PVNoxytocin -CeA projections in the regulation of anxiety-like behaviors induced by inflammatory pain.

The structural and functional complexity of the integrative hypothalamus

The hypothalamus ("hypo" meaning below, and "thalamus" meaning bed) consists of regulatory circuits that support basic life functions that ensure survival. Sitting at the interface between peripheral, environmental, and neural inputs, the hypothalamus integrates these sensory inputs to influence a range of physiologies and behaviors. Unlike the neocortex, in which a stereotyped cytoarchitecture mediates complex functions across a comparatively small number of neuronal fates, the hypothalamus comprises upwards of thousands of distinct cell types that form redundant yet functionally discrete circuits. With single-cell RNA sequencing studies revealing further cellular heterogeneity and modern photonic tools enabling high-resolution dissection of complex circuitry, a new era of hypothalamic mapping has begun. Here, we provide a general overview of mammalian hypothalamic organization, development, and connectivity to help welcome newcomers into this exciting field.

Dysregulated neuromodulation in the anterior cingulate cortex in chronic pain

Chronic pain is a significant global socioeconomic burden with limited long-term treatment options. The intractable nature of chronic pain stems from two primary factors: the multifaceted nature of pain itself and an insufficient understanding of the diverse physiological mechanisms that underlie its initiation and maintenance, in both the peripheral and central nervous systems. The development of novel non-opioidergic analgesic approaches is contingent on our ability to normalize the dysregulated nociceptive pathways involved in pathological pain processing. The anterior cingulate cortex (ACC) stands out due to its involvement in top-down modulation of pain perception, its abnormal activity in chronic pain conditions, and its contribution to cognitive functions frequently impaired in chronic pain states. Here, we review the roles of the monoamines dopamine (DA), norepinephrine (NE), serotonin (5-HT), and other neuromodulators in controlling the activity of the ACC and how chronic pain alters their signaling in ACC circuits to promote pathological hyperexcitability. Additionally, we discuss the potential of targeting these monoaminergic pathways as a therapeutic strategy for treating the cognitive and affective symptoms associated with chronic pain.

Activation of the TNF-α-Necroptosis Pathway in Parvalbumin-Expressing Interneurons of the Anterior Cingulate Cortex Contributes to Neuropathic Pain

The hyperexcitability of the anterior cingulate cortex (ACC) has been implicated in the development of chronic pain. As one of the key causes of ACC hyperexcitation, disinhibition of the ACC may be closely related to the dysfunction of inhibitory parvalbumin (PV)-expressing interneurons (PV-INs). However, the molecular mechanism underlying the ACC PV-INs injury remains unclear. The present study demonstrates that spared sciatic nerve injury (SNI) induces an imbalance in the excitation and inhibition (E/I) of the ACC. To test whether tumor necrosis factor-α (TNF-α) upregulation in the ACC after SNI activates necroptosis and participates in PV-INs damage, we performed a differential analysis of transcriptome sequencing using data from neuropathic pain models and found that the expression of genes key to the TNF-α-necroptosis pathway were upregulated. TNF-α immunoreactivity (IR) signals in the ACCs of SNI rats were co-located with p-RIP3- and PV-IR, or p-MLKL- and PV-IR signals. We then systematically detected the expression and cell localization of necroptosis-related proteins, including kinase RIP1, RIP3, MLKL, and their phosphorylated states, in the ACC of SNI rats. Except for RIP1 and MLKL, the levels of these proteins were significantly elevated in the contralateral ACC and mainly expressed in PV-INs. Blocking the ACC TNF-α-necroptosis pathway by microinjecting TNF-α neutralizing antibody or using an siRNA knockdown to block expression of MLKL in the ACC alleviated SNI-induced pain hypersensitivity and inhibited the upregulation of TNF-α and p-MLKL. Targeting TNF-α-triggered necroptosis within ACC PV-INs may help to correct PV-INs injury and E/I imbalance in the ACC in neuropathic pain.

Nitric oxide synthase contributes to the maintenance of LTP in the oxytocin-mRFP1 neuron of the rat hypothalamus

Oxytocin (OXT) is a neuropeptide hormone that plays a critical role in nociception. Long-term potentiation (LTP) is a major form of synaptic plasticity in the central nervous system. Recently, LTP has been reported in the hypothalamus; however, data on LTP in hypothalamic OXT-ergic neurons are unclear. Furthermore, the signaling pathways for hypothalamic OXT-ergic neuronal LTP and its physiological significance remain unknown. Herein, we aimed to investigate the induction of hypothalamic OXT-ergic neuronal LTP and its synaptic mechanism using OXT-monomeric red fluorescent protein 1 transgenic rats to visualize and record from OXT-ergic neurons. The hypothalamic paraventricular nucleus (PVN) OXT-ergic neuronal LTP induced by the pairing protocol was dependent on N-methyl-D-aspartate receptor (NMDAR). Furthermore, nitric oxide synthase (NOS) is required to maintain the LTP regardless of the NMDARs. In addition, hypothalamic OXT-ergic neuronal LTP was not induced in the adjuvant arthritis rat model but increased excitatory postsynaptic currents were detected. LTP in hypothalamic OXT-ergic neurons in the PVN in the presence of NOS may be involved in neuronal changes during OXT synthesis in chronic inflammation.

Janus effect of the anterior cingulate cortex: Pain and emotion

Over the past 20 years, clinical and preclinical studies point to the anterior cingulate cortex (ACC) as a site of interest for several neurological and psychiatric conditions. The ACC plays a critical role in emotion, autonomic regulation, pain processing, attention, memory and decision making. An increasing number of studies have demonstrated the involvement of the ACC in the emotional component of pain and its comorbidity with emotional disorders such as anxiety and depression. Thanks to the development of animal models combined with state-of-the-art technologies, we now have a better mechanistic understanding of the functions of the ACC. Hence, the primary aim of this review is to compile the most recent preclinical studies on the role of ACC in the emotional component and consequences of chronic pain. Herein, we thus thoroughly describe the pain-induced electrophysiological, molecular and anatomical alterations in the ACC and in its related circuits. Finally, we discuss the next steps that are needed to strengthen our understanding of the involvement of the ACC in emotional and pain processing.

The role of the oxytocin system in the resilience of patients with breast cancer

Breast cancer is a grave traumatic experience that can profoundly compromise patients' psychological resilience, impacting their overall quality of life. The oxytocin system represents one of the essential neurobiological bases of psychological resilience and plays a critical role in regulating resilience in response to social or traumatic events during adulthood. Oxytocin, through its direct interaction with peripheral or central oxytocin receptors, has been found to have a significant impact on regulating social behavior. However, the precise mechanism by which the activation of peripheral oxytocin receptors leads to improved social is still not completely comprehended and requires additional research. Its activation can modulate psychological resilience by influencing estrogen and its receptors, the hypothalamic-pituitary-adrenal axis, thyroid function, 5-hydroxytryptamine metabolism levels, and arginine pressure release in breast cancer patients. Various interventions, including psychotherapy and behavioral measures, have been employed to improve the psychological resilience of breast cancer patients. The potential effectiveness of such interventions may be underpinned by their ability to modulate oxytocin release levels. This review provides an overview of the oxytocin system and resilience in breast cancer patients and identifies possible future research directions and interventions.

Brain nuclei and neural circuits in neuropathic pain and brain modulation mechanisms of acupuncture: a review on animal-based experimental research

Neuropathic pain (NP) is known to be associated with abnormal changes in specific brain regions, but the complex neural network behind it is vast and complex and lacks a systematic summary. With the help of various animal models of NP, a literature search on NP brain regions and circuits revealed that the related brain nuclei included the periaqueductal gray (PAG), lateral habenula (LHb), medial prefrontal cortex (mPFC), and anterior cingulate cortex (ACC); the related brain circuits included the PAG-LHb and mPFC-ACC. Moreover, acupuncture and injurious information can affect different brain regions and influence brain functions via multiple aspects to play an analgesic role and improve synaptic plasticity by regulating the morphology and structure of brain synapses and the expression of synapse-related proteins; maintain the balance of excitatory and inhibitory neurons by regulating the secretion of glutamate, γ-aminobutyric acid, 5-hydroxytryptamine, and other neurotransmitters and receptors in the brain tissues; inhibit the overactivation of glial cells and reduce the release of pro-inflammatory mediators such as interleukins to reduce neuroinflammation in brain regions; maintain homeostasis of glucose metabolism and regulate the metabolic connections in the brain; and play a role in analgesia through the mediation of signaling pathways and signal transduction molecules. These factors help to deepen the understanding of NP brain circuits and the brain mechanisms of acupuncture analgesia.

Pain in Huntington's disease and its potential mechanisms

Pain is common and frequent in many neurodegenerative diseases, although it has not received much attention. In Huntington's disease (HD), pain is often ignored and under-researched because attention is more focused on motor and cognitive decline than psychiatric symptoms. In HD progression, pain symptoms are complex and involved in multiple etiologies, particularly mental issues such as apathy, anxiety and irritability. Because of psychiatric issues, HD patients rarely complain of pain, although their bodies show severe pain symptoms, ultimately resulting in insufficient awareness and lack of research. In HD, few studies have focused on pain and pain-related features. A detailed and systemic pain history is crucial to assess and explore pain pathophysiology in HD. This review provides an overview concentrating on pain-related factors in HD, including neuropathology, frequency, features, affecting factors and mechanisms. More attention and studies are still needed in this interesting field in the future.

The Role of Oxytocin in Early-Life-Stress-Related Neuropsychiatric Disorders

Early-life stress during critical periods of brain development can have long-term effects on physical and mental health. Oxytocin is a critical social regulator and anti-inflammatory hormone that modulates stress-related functions and social behaviors and alleviates diseases. Oxytocin-related neural systems show high plasticity in early postpartum and adolescent periods. Early-life stress can influence the oxytocin system long term by altering the expression and signaling of oxytocin receptors. Deficits in social behavior, emotional control, and stress responses may result, thus increasing the risk of anxiety, depression, and other stress-related neuropsychiatric diseases. Oxytocin is regarded as an important target for the treatment of stress-related neuropsychiatric disorders. Here, we describe the history of oxytocin and its role in neural circuits and related behaviors. We then review abnormalities in the oxytocin system in early-life stress and the functions of oxytocin in treating stress-related neuropsychiatric disorders.

Loosely synchronized activation of anterior cingulate cortical neurons for scratching response during histamine-induced itch

Itch is a distinctive sensation that causes a specific affection and scratching reaction. The anterior cingulate cortex (ACC) has been linked to itch sensation in numerous studies; however, its precise function in processing pruritic inputs remains unknown. Distinguishing the precise role of the ACC in itch sensation can be challenging because of its capacity to conduct heterologous neurophysiological activities. Here, we used in vivo calcium imaging to examine how ACC neurons in free-moving mice react to pruritogenic histamine. In particular, we focused on how the activity of the ACC neurons varied before and after the scratching response. We discovered that although the change in neuronal activity was not synchronized with the scratching reaction, the overall activity of itch-responsive neurons promptly decreased after the scratching response. These findings suggest that the ACC does not directly elicit the feeling of itchiness.

Up-regulation of LCN2 in the anterior cingulate cortex contributes to neural injury-induced chronic pain

Chronic pain caused by disease or injury affects more than 30% of the general population. The molecular and cellular mechanisms underpinning the development of chronic pain remain unclear, resulting in scant effective treatments. Here, we combined electrophysiological recording, in vivo two-photon (2P) calcium imaging, fiber photometry, Western blotting, and chemogenetic methods to define a role for the secreted pro-inflammatory factor, Lipocalin-2 (LCN2), in chronic pain development in mice with spared nerve injury (SNI). We found that LCN2 expression was upregulated in the anterior cingulate cortex (ACC) at 14 days after SNI, resulting in hyperactivity of ACC glutamatergic neurons (ACC^Glu) and pain sensitization. By contrast, suppressing LCN2 protein levels in the ACC with viral constructs or exogenous application of neutralizing antibodies leads to significant attenuation of chronic pain by preventing ACC^Glu neuronal hyperactivity in SNI 2W mice. In addition, administering purified recombinant LCN2 protein in the ACC could induce pain sensitization by inducing ACC^Glu neuronal hyperactivity in naïve mice. This study provides a mechanism by which LCN2-mediated hyperactivity of ACC^Glu neurons contributes to pain sensitization, and reveals a new potential target for treating chronic pain.

Plasticity of cortico-striatal neurons of the caudal anterior cingulate cortex during experimental neuropathic pain

Maladaptive neuronal plasticity is a main mechanism for the development and maintenance of pathological pain. Affective, motivational and cognitive deficits that are comorbid with pain involve cellular and synaptic modifications in the anterior cingulate cortex (ACC), a major brain mediator of pain perception. Here we use a model of neuropathic pain (NP) in male mice and ex-vivo electrophysiology to investigate whether layer 5 caudal ACC (cACC) neurons projecting to the dorsomedial striatum (DMS), a critical region for motivational regulation of behavior, are involved in aberrant neuronal plasticity. We found that while the intrinsic excitability of cortico-striatal cACC neurons (cACC-CS) was preserved in NP animals, excitatory postsynaptic potentials (EPSP) induced after stimulation of distal inputs were enlarged. The highest synaptic responses were evident both after single stimuli and in each of the EPSP that compose responses to trains of stimuli, and were accompanied by increased synaptically-driven action potentials. EPSP temporal summation was intact in ACC-CS neurons from NP mice, suggesting that the plastic changes were not due to alterations in dendritic integration but rather through synaptic mechanisms. These results demonstrate for the first time that NP affects cACC neurons that project to the DMS and reinforce the notion that maladaptive plasticity of the cortico-striatal pathway may be a key factor in sustaining pathological pain.

Evaluation of the effectiveness of oxytocin and enalapril in the prevention of epidural fibrosis developed after laminectomy in rats

INTRODUCTION

Except for methylprednisolone, there is no current low-cost and low-side-effect drug/barrier method to prevent epidural fibrosis after spine surgery. However, the use of methylprednisolone has led to substantial controversy because of its serious side effects on wound healing. This study aimed to evaluate the effects of enalapril and oxytocin on preventing the development of epidural fibrosis in a rat laminectomy model.

MATERIALS

Under sedation anesthesia, T9, T10, and T11 laminectomy was performed on 24 Wistar Albino male rats. The animals were then separated into four groups; Sham group (only laminectomy was performed; n = 6), MP group (laminectomy was performed and 10 mg/kg/day methylprednisolone was administered intraperitoneally (ip) for 14 days; n = 6), ELP group (laminectomy was performed and 0.75 mg/kg/day enalapril was administered ip for 14 days; n = 6), OXT group (laminectomy was performed and 160 µg/kg/day oxytocin was administered ip for 14 days; n = 6). Four weeks after the laminectomy, all the rats were euthanised, and the spines were removed for histopathological, immunohistochemical, and biochemical examinations.

RESULTS

Histopathological examinations revealed that the degree of epidural fibrosis (X²=14.316, p = 0.003), collagen density (X²=16.050, p = 0.001), and fibroblast density (X²=17.500, p = 0.001) was higher in the Sham group and lower in the MP, ELP, and OXT groups. Immunohistochemical examinations showed that collagen type 1 immunoreactivity was higher in the Sham group and lower in the MP, ELP, and OXT groups (F = 54.950, p < 0.001). The highest level of α-smooth muscle actin immunoreactivity was seen in the Sham and OXT groups, and the lowest was in the MP and ELP groups (F = 33.357, p < 0.001). Biochemical analysis revealed that tissue levels of TNF-α, TGF-β, IL-6, CTGF, caspase-3, p-AMPK, pmTOR, and mTOR/pmTOR were higher in the Sham group and lower in MP, ELP, and OXT groups (p < 0.05). The GSH/GSSG levels were lower in the Sham group and higher in the other three groups (X²=21.600, p < 0.001).

CONCLUSION

The study results showed that enalapril and oxytocin, which are known to have anti-inflammatory, antioxidant, anti-apoptotic, and autophagy-related regenerative properties, could reduce the development of epidural fibrosis after laminectomy in rats.

Effects of Danggui-Shaoyao-San on central neuroendocrine and pharmacokinetics in female ovariectomized rats

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Chinese medicine formula Danggui-Shaoyao-San (DSS) has been reported to have estrogen-like effects and therapeutic effects on the symptoms of Alzheimer's disease (AD).

AIM OF THE STUDY

To explore whether the central oxytocin and neuroendocrine system is involved in the modulating effects of DSS on the cognition and neuropsychiatric hebaviors in female AD rats, and to investigate the pharmacokinetics of paeoniflorin and ferulic acid in female AD rats with DSS treatment.

MATERIAL AND METHODS

DSS (1.2, 3.2, 8.6g/kg/day) was orally administered to ovariectomized (OVX) rats, and saline was orally administered to sham operation rats as control group. The Morris water maze test, novel object recognition test, and passive avoidance test were conducted for evaluation of learning and memory abilities, while elevated plus maze test and forced swim test were performed to assess anxiety- and depressive-like behaviors. ELISA kits were used to detect the levels of estrogen (E), estrogen receptor α (ERα), oxytocin (OT), oxytocin receptor (OTR), acetylcholine (Ach), acetylcholin esterase (AchE), and choline acetyl transferase (ChAT) in the cortex. The concentrations of Ach, glutamate (Glu), γ-aminobutyric acid (GABA), 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine (DA) in the hippocampus were assessed by HPLC-MS. The changes of neuronal morphology in the hippocampus were observed by Nissl staining. The pharmacokinetics of paeoniflorin and ferulic acid in OVX rats with DSS treatment were studied by HPLC.

RESULTS

In the Morris water maze test, novel object recognition test, and passive avoidance test, OVX rats showed cognitive impairment. In the elevated plus maze test and forced swim test, the anxiety- and depressive-like behaviors of OVX rats were significant as compared to the control group. Treatment of DSS significantly imporved the cognitive deficits, and ameliorated anxiety- and depressive-like behaviors of OVX rats. The expression of E, ERα, OT, OTR, AchE and ChAT in the cortex of model group were significantly decreased, and DSS significantly reversed these changes. The concentrations of Ach, Glu, GABA, 5-HT and NE in the hippocampus of OVX rats were significantly decreased, whereas DSS significantly increased the levels of Ach, Glu, GABA, 5-HT and NE. There was no significant difference in the concentration of DA in the hippocampus among groups. Degenerating neurons in the hippocampal CA3 region were observed in OVX rats, and the number of neurons was decreased. DSS treatment reduced the degenerating neurons, and incresed the number of neurons. The MRT (0 - ∞), AUC (0 - ∞), Cmax and t1/2z values of paeoniflorin, and the AUC _0-∞ and C_max value of ferulic acid were higher in DSS-treated OVX rats than those in the DSS-treated control rats.

CONCLUSIONS

DSS improves the learning and memory ability, and attenuates anxiety- and depressive-like behaviors of OVX rats. The mechanism may be through increasing estrogen, reducing cholinergic damage, and modulating neurotransmitters. The increase in absorption and elimination time of paeoniflorin and ferulic acid in OVX rats may enhance the efficacy of DSS.

Advances in the Electrophysiological Recordings of Long-Term Potentiation

Understanding neuronal firing patterns and long-term potentiation (LTP) induction in studying learning, memory, and neurological diseases is critical. However, recently, despite the rapid advancement in neuroscience, we are still constrained by the experimental design, detection tools for exploring the mechanisms and pathways involved in LTP induction, and detection ability of neuronal action potentiation signals. This review will reiterate LTP-related electrophysiological recordings in the mammalian brain for nearly 50 years and explain how excitatory and inhibitory neural LTP results have been detected and described by field- and single-cell potentials, respectively. Furthermore, we focus on describing the classic model of LTP of inhibition and discuss the inhibitory neuron activity when excitatory neurons are activated to induce LTP. Finally, we propose recording excitatory and inhibitory neurons under the same experimental conditions by combining various electrophysiological technologies and novel design suggestions for future research. We discussed different types of synaptic plasticity, and the potential of astrocytes to induce LTP also deserves to be explored in the future.

Protective effect of Nr4a2 (Nurr1) against LPS-induced depressive-like behaviors via regulating activity of microglia and CamkII neurons in anterior cingulate cortex

Neuroinflammation is tightly associated with onset of depression. The nuclear receptor related 1 protein (Nurr1, also called Nr4a2), its roles in dopaminergic neurons is well understood, which can alleviate inflammation. Nevertheless, potential effects of Nr4a2 on neuroinflammation associated with depression still remains unclear. Chronic lipopolysaccharides (LPS) stress induced depressive-behaviors were confirmed via behavioral tests. Differentially expressed genes were detected by using RNA-sequencing. The anterior cingulate cortex (ACC) tissues were collected for biochemical experiments. The Golgi-Cox staining and virus labeling were used to evaluate the dendritic spines. We applied fluoxetine (FLX) and amodiaquine dihydrochloride (AQ, a highly selective agonist of Nr4a2) in mice. Overexpression experiments were performed by injecting with AAV-Nr4a2-EGFP into ACC. Chemogenetic activation of CamkII neurons via injecting the hM3Dq virus. Mice treated with LPS displayed depressive- and anxiety-like behaviors. The reduction of Nr4a2 and FosB induced by LPS were rescued by pretreatment with FLX or AQ. More importantly, LPS-induced behavior deficits in mice were also alleviated via fluoxetine treatment and pharmacological activation the expression of Nr4a2. Meanwhile, enhancing the level of Nr4a2 could improve dendritic spines loss of neuron and morphological changes in microglia. Overexpression of Nr4a2 in ACC reversed the depressive- and anxiety-like behaviors caused by LPS administration. Activation of CamkII neurons in ACC could robustly increase the expression of Nr4a2 and improve LPS-induced behavior deficits. Our findings demonstrate that the Nr4a2 may regulate depressive-like behaviors via alleviating the impairment of morphology and function on microglia and CamkII neurons induced by chronic neuroinflammation.

A paraventricular hypothalamic nucleus input to ventral of lateral septal nucleus controls chronic visceral pain

ABSTRACT

Irritable bowel syndrome is a functional gastrointestinal disorder characterized by chronic visceral pain with complex etiology and difficult treatment. Accumulated evidence has confirmed that the sensitization of the central nervous system plays an important role in the development of visceral pain, whereas the exact mechanisms of action of the neural pathways remain largely unknown. In this study, a distinct neural circuit was identified from the paraventricular hypothalamic (PVH) to the ventral of lateral septal (LSV) region. This circuit was responsible for regulating visceral pain. In particular, the data indicated that the PVH CaMKIIα-positive neurons inputs to the LSV CaMKIIα-positive neurons were only activated by colorectal distention rather than somatic stimulations. The PVH-LSV CaMKIIα + projection pathway was further confirmed by experiments containing a viral tracer. Optogenetic inhibition of PVH CaMKIIα + inputs to LSV CaMKIIα-positive neurons suppressed visceral pain, whereas selective activation of the PVH-LSV CaMKIIα + projection evoked visceral pain. These findings suggest the critical role of the PVH-LSV CaMKIIα + circuit in regulating visceral pain.

The effect of acupuncture at the Yuji point on resting-state brain function in anxiety

BACKGROUND

The COVID-19 epidemic has placed a lot of mental burdens on school students, causing anxiety. Clinically, it has been found that the Yuji point (LU10) can relieve anxiety by regulating Qi.

METHODS

Thirty-six volunteers with anxiety disorders were divided into 3 groups, all of whom underwent 2 MRI examinations. The Yuji and nonacupoint groups received acupuncture between functional magnetic resonance imagings. We used the amplitude of low-frequency fluctuation to analyze regional brain activity, and seed-based functional connectivity (FC) to analyze changes in brain networks.

RESULTS

After acupuncture, the LU10 was able to activate the frontal lobe, medial frontal gyrus, anterior cingulate gyrus, temporal lobe, hippocampus, etc in the left brain compared to the control group. The frontal lobe, medial frontal gyrus, cingulate gyrus, and anterior cingulate gyrus in the left brain were activated compared to those in the nonacupoint group. Compared with the control group, LU10 showed increased FC in the right parietal lobe, right precuneus, left temporal lobe, left superior temporal gyrus, and with cingulate gyrus. FC was enhanced among the hippocampus with the left temporal lobe and the superior temporal gyrus and reduced in the right lingual gyrus and right occipital lobe.

CONCLUSION

Acupuncture at LU10s can regulate anxiety by upregulating or downregulating the relevant brain regions and networks. LU10s can be used to treat not only lung disorders but also related mental disorders.

Protective Role and Functional Engineering of Neuropeptides in Depression and Anxiety: An Overview

Behavioral disorders, such as anxiety and depression, are prevalent globally and touch children and adults on a regular basis. Therefore, it is critical to comprehend how these disorders are affected. It has been demonstrated that neuropeptides can influence behavior, emotional reactions, and behavioral disorders. This review highlights the majority of the findings demonstrating neuropeptides' behavioral role and functional engineering in depression and anxiety. Gut-brain peptides, hypothalamic releasing hormone peptides, opioid peptides, and pituitary hormone peptides are the four major groups of neuropeptides discussed. Some neuropeptides appear to promote depression and anxiety-like symptoms, whereas others seem to reduce it, all depending on the receptors they are acting on and on the brain region they are localized in. The data supplied here are an excellent starting point for future therapy interventions aimed at treating anxiety and depression.

Altered brain activities in mesocorticolimbic pathway in primary dysmenorrhea patients of long-term menstrual pain

Background

Patients with primary dysmenorrhea (PDM) often present with abnormalities other than dysmenorrhea including co-occurrence with other chronic pain conditions and central sensitization. Changes in brain activity in PDM have been demonstrated; however, the results are not consistent. Herein, this study probed into altered intraregional and interregional brain activity in patients with PDM and expounded more findings.

Methods

A total of 33 patients with PDM and 36 healthy controls (HCs) were recruited and underwent a resting-state functional magnetic resonance imaging scan. Regional homogeneity (ReHo) and mean amplitude of low-frequency fluctuation (mALFF) analysis were applied to compare the difference in intraregional brain activity between the two groups, and the regions with ReHo and mALFF group differences were used as seeds for functional connectivity (FC) analysis to explore the difference of interregional activity. Pearson's correlation analysis was conducted between rs-fMRI data and clinical symptoms in patients with PDM.

Results

Compared with HCs, patients with PDM showed altered intraregional activity in a series of brain regions, including the hippocampus, the temporal pole superior temporal gyrus, the nucleus accumbens, the pregenual anterior cingulate cortex, the cerebellum_8, the middle temporal gyrus, the inferior temporal gyrus, the rolandic operculum, the postcentral gyrus and the middle frontal gyrus (MFG), and altered interregional FC mainly between regions of the mesocorticolimbic pathway and regions associated with sensation and movement. The anxiety symptoms are correlated with the intraregional activity of the right temporal pole superior temporal gyrus and FC between MFG and superior frontal gyrus.

Conclusion

Our study showed a more comprehensive method to explore changes in brain activity in PDM. We found that the mesocorticolimbic pathway might play a key role in the chronic transformation of pain in PDM. We, therefore, speculate that the modulation of the mesocorticolimbic pathway may be a potential novel therapeutic mechanism for PDM.

Up-regulation of oxytocin receptors on peripheral sensory neurons mediates analgesia in chemotherapy-induced neuropathic pain

BACKGROUND AND PURPOSE

Chemotherapy-induced neuropathic pain (CINP) currently has limited effective treatment. Although the roles of oxytocin (OXT) and the oxytocin receptor (OXTR) in central analgesia have been well documented, the expression and function of OXTR in the peripheral nervous system remain unclear. Here, we evaluated the peripheral antinociceptive profiles of OXTR in CINP.

EXPERIMENTAL APPROACH

Paclitaxel (PTX) was used to establish CINP. Quantitative real-time polymerase chain reaction (qRT-PCR), in situ hybridization, and immunohistochemistry were used to observe OXTR expression in dorsal root ganglia (DRG). The antinociceptive effects of OXT were assessed by hot-plate and von Frey tests. Whole-cell patch clamp was performed to record sodium currents, excitability of DRG neurons, and excitatory synapse transmission.

KEY RESULTS

Expression of OXTR in DRG neurons was enhanced significantly after PTX treatment. Activation of OXTR exhibited antinociceptive effects, by decreasing the hyperexcitability of DRG neurons in PTX-treated mice. Additionally, OXTR activation up-regulated the phosphorylation of protein kinase C (pPKC) and, in turn, impaired voltage-gated sodium currents, particularly the voltage-gated sodium channel 1.7 (Na_V 1.7) current, that plays an indispensable role in PTX-induced neuropathic pain. OXT suppressed excitatory transmission in the spinal dorsal horn as well as excitatory inputs from primary afferents in PTX-treated mice.

CONCLUSION AND IMPLICATIONS

The OXTR in small-sized DRG neurons is up-regulated in CINP and its activation relieved CINP by inhibiting the neural excitability by impairment of Na_V 1.7 currents via pPKC. Our results suggest that OXTR on peripheral sensory neurons is a potential therapeutic target to relieve CINP.