GluA1 in Central Amygdala Promotes Opioid Use and Reverses Inhibitory Effect of Pain

A novel role for microtubule affinity-regulating kinases in neuropathic pain

BACKGROUND AND PURPOSE

Neuropathic pain affects millions of patients, but there are currently few viable therapeutic options available. Microtubule affinity-regulating kinases (MARKs) regulate the dynamics of microtubules and participate in synaptic remodelling. It is unclear whether these changes are involved in the central sensitization of neuropathic pain. This study examined the role of MARK1 or MARK2 in regulating neurosynaptic plasticity induced by neuropathic pain.

EXPERIMENTAL APPROACH

A rat spinal nerve ligation (SNL) model was established to induce neuropathic pain. The role of MARKs in nociceptive regulation was assessed by genetically knocking down MARK1 or MARK2 in amygdala and systemic administration of PCC0105003, a novel small molecule MARK inhibitor. Cognitive function, anxiety-like behaviours and motor coordination capability were also examined in SNL rats. Synaptic remodelling-associated signalling changes were detected with electrophysiological recording, Golgi-Cox staining, western blotting and qRT-PCR.

KEY RESULTS

MARK1 and MARK2 expression levels in amygdala and spinal dorsal horn were elevated in SNL rats. MARK1 or MARK2 knockdown in amygdala and PCC0105003 treatment partially attenuated pain-like behaviours along with improving cognitive deficit, anxiogenic-like behaviours and motor coordination in SNL rats. Inhibition of MARKs signalling reversed synaptic plasticity at the functional and structural levels by suppressing NR2B/GluR1 and EB3/Drebrin signalling pathways both in amygdala and spinal dorsal horn.

CONCLUSION AND IMPLICATIONS

These results suggest that MARKs-mediated synaptic remodelling plays a key role in the pathogenesis of neuropathic pain and that pharmacological inhibitors of MARKs such as PCC0105003 could represent a novel therapeutic strategy for the management of neuropathic pain.

Exercise Therapy Research in Ankylosing Spondylitis-Induced Back Pain: A Bibliometric Study (2004-2023)

BACKGROUND Ankylosing spondylitis (AS), a chronic inflammatory disease predominantly causing back pain, affects up to 0.5% of the global population, more commonly in males. Frequently undiagnosed in early stages, AS is often associated with comorbid depression and anxiety, imposing significant healthcare burdens. Despite available pharmaceutical treatments, exercise therapy (ET) has emerged as an effective, side-effect-free alternative, particularly for managing AS-induced back pain. This study aims to explore the research trends in ET for treating AS back pain from 2004-2023. MATERIAL AND METHODS A comprehensive analysis of 437 articles, sourced from the Science Citation Index-Expanded within the Web of Science Core Collection, was conducted using CiteSpace 6.2.R5. This study spanned from 2004 to October 15, 2023, examining publications, authors, institutions, and keywords to assess keyword co-occurrences, temporal progressions, and citation bursts. RESULTS Research interest in ET for AS began escalating around 2008 and has since shown steady growth. The USA emerged as a significant contributor, with Van der Heijde, Desiree, and RUDWALEIT M being notable authors. Key institutions include Assistance Publique Hopitaux Paris and UDICE-French Research Universities, with ANN RHEUM DIS being the most influential journal. The field's evolution is marked by interdisciplinary integration and branching into various sub-disciplines. CONCLUSIONS Exercise therapy for AS-induced back pain is a growing research area, necessitating further exploration in clinical management and rehabilitation strategies. The relationship between ET and osteoimmunological mechanisms remains a focal point for future research, with a trend towards personalized and interdisciplinary treatment approaches.

The excitatory transmission from basolateral nuclues of amygdala to nucleus accumbens shell regulates propofol self-administration through AMPA receptors

Propofol addictive properties have been demonstrated in humans and rats. The glutamatergic transmission from basolateral nucleus of amygdala (BLA) to the nucleus accumbens (NAc) modulates reward-seeking behaviour; especially, NAc shell (NAsh) is implicated in reward-seeking response. Previous studies indicated the interactions between AMPA receptors (AMPARs) and dopamine D1 receptor (D1R) in NAc mediated drug addiction, but whether the circuit of BLA-to-NAsh and AMPARs regulate propofol addiction remains unclear. We trained adult male Sprague-Dawley rats for propofol self-administration to examine the changes of action potentials (APs) and spontaneous excitatory postsynaptic currents (sEPSCs) in the NAsh. Thereafter, optogenetic stimulation with adeno-associated viral vectors microinjections in BLA was used to explore the effect of BLA-to-NAsh on propofol self-administration behaviour (1.7 mg/kg/injection). The pretreatment effects with NBQX (0.25-1.0 μg/0.3 μl/site) or vehicle in the NAsh on propofol self-administration behaviour, the expressions of AMPARs subunits and D1R/ERK/CREB signalling pathway in the NAc were detected. The results showed that the number of APs, amplitude and frequency of sEPSCs were enhanced in propofol self-administrated rats. Propofol self-administration was inhibited in the NpHR3.0-EYFP group, but in the ChR2-EYFP group, there was a promoting effect, which could be weakened by NBQX pretreatment. NBQX pretreatment also significantly decreased the expressions of GluA2 subunit and D1R in the NAc but did not change the expressions of GluA1 and ERK/CREB signalling pathway. The evidence supports a vital role of BLA-to-NAsh circuit in regulating propofol self-administration and suggests this central reward processing may function through the interaction between AMPARs and D1R in the NAsh.

Bibliometric Analysis of Functional Magnetic Resonance Imaging Studies on Manual Therapy Analgesia from 2002-2022

Background

Research on the brain mechanisms underlying manual therapy (MT)-induced analgesia has been conducted worldwide. However, no bibliometric analysis has been performed on functional magnetic resonance imaging (fMRI) studies of MT analgesia. To provide a theoretical foundation for the practical application of MT analgesia, this study examined the current incarnation, hotspots, and frontiers of fMRI-based MT analgesia research over the previous 20 years.

Methods

All publications were obtained from the Science Citation Index-Expanded (SCI-E) of Web of Science Core Collection (WOSCC). We used CiteSpace 6.1.R3 to analyze publications, authors, cited authors, countries, institutions, cited journals, references, and keywords. We also evaluated keyword co-occurrences and timelines, and citation bursts. The search was conducted from 2002-2022 and was completed within one day on October 7, 2022.

Results

In total, 261 articles were retrieved. The total number of annual publications showed a fluctuating but overall increasing trend. Author B. Humphreys had the highest number of publications (eight articles) and J. E. Bialosky had the highest centrality (0.45). The United States of America (USA) was the country with the most publications (84 articles), accounting for 32.18% of all publications. Output institutions were mainly the University of Zurich, University of Switzerland, and the National University of Health Sciences of the USA. The Spine (118) and the Journal of Manipulative and Physiological Therapeutics (80) were most frequently cited. The four hot topics in fMRI studies on MT analgesia were "low back pain", "magnetic resonance imaging", "spinal manipulation", and "manual therapy." The frontier topics were "clinical impacts of pain disorders" and "cutting-edge technical capabilities offered by magnetic resonance imaging".

Conclusion

fMRI studies of MT analgesia have potential applications. fMRI studies of MT analgesia have linked several brain areas, with the default mode network (DMN) garnering the most attention. Future research should include international collaboration and RCTs on this topic.

Structural Investigation of the Interaction Mechanism between Chlorogenic Acid and AMPA Receptor via In Silico Approaches

Chlorogenic acid (CGA), an important metabolite in natural plant medicines such as honeysuckle and eucommia, has been shown to have potent antinociceptive effects. Nevertheless, the mechanism by which CGA relieves chronic pain remains unclear. α-amino-3-hydroxy-5-methyl-4-isooxazolpropionic acid receptor (AMPAR) is a major ionotropic glutamate receptor that mediates rapid excitatory synaptic transmission and its glutamate ionotropic receptor AMPA type subunit 1 (GluA1) plays a key role in nociceptive transmission. In this study, we used Western blot, surface plasmon resonance (SPR) assay, and the molecular simulation technologies to investigate the mechanism of interaction between CGA and AMPAR to relieve chronic pain. Our results indicate that the protein expression level of GluA1 showed a dependent decrease as the concentration of CGA increased (0, 50, 100, and 200 μM). The SPR assay demonstrates that CGA can directly bind to GluA1 (K_D = 496 μM). Furthermore, CGA forms a stable binding interaction with GluA1, which is validated by molecular dynamics (MD) simulation. The binding free energy between CGA and GluA1 is -39.803 ± 14.772 kJ/mol, where van der Waals interaction and electrostatic interaction are the major contributors to the GluA1-CGA binding, and the key residues are identified (Val-32, Glu-33, Ala-36, Glu-37, Leu-48), which play a crucial role in the binding interaction. This study first reveals the structural basis of the stable interaction between CGA and GluA1 to form a binding complex for the relief of chronic pain. The research provides the structural basis to understand the treatment of chronic pain and is valuable to the design of novel drug molecules in the future.

Endogenous opiates and behavior: 2019

This paper is the forty-second consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2019 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Bidirectional Dysregulation of AMPA Receptor-Mediated Synaptic Transmission and Plasticity in Brain Disorders

AMPA receptors (AMPARs) are glutamate-gated ion channels that mediate the majority of fast excitatory synaptic transmission throughout the brain. Changes in the properties and postsynaptic abundance of AMPARs are pivotal mechanisms in synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission. A wide range of neurodegenerative, neurodevelopmental and neuropsychiatric disorders, despite their extremely diverse etiology, pathogenesis and symptoms, exhibit brain region-specific and AMPAR subunit-specific aberrations in synaptic transmission or plasticity. These include abnormally enhanced or reduced AMPAR-mediated synaptic transmission or plasticity. Bidirectional reversal of these changes by targeting AMPAR subunits or trafficking ameliorates drug-seeking behavior, chronic pain, epileptic seizures, or cognitive deficits. This indicates that bidirectional dysregulation of AMPAR-mediated synaptic transmission or plasticity may contribute to the expression of many brain disorders and therefore serve as a therapeutic target. Here, we provide a synopsis of bidirectional AMPAR dysregulation in animal models of brain disorders and review the preclinical evidence on the therapeutic targeting of AMPARs.