The Downregulation of Opioid Receptors and Neuropathic Pain

Aripiprazole: The antiallodynic and antihyperalgesic effects in chronic constriction injury-induced neuropathic pain and reserpine-induced fibromyalgia with possible mechanisms

Neuropathic pain, caused by peripheral or central nerve damage, and fibromyalgia, a chronic musculoskeletal disorder, require complex treatment approaches. This study evaluated the antiallodynic and antihyperalgesic effects of aripiprazole (1, 5, and 10 mg/kg, i. p.) in rats with chronic constriction injury-induced neuropathic pain and reserpine-induced fibromyalgia in female Sprague-Dawley rats, using electronic von Frey and Hargreaves tests. Dopaminergic, serotonergic, and opioidergic systems' roles were assessed through pre-treatment with sulpiride (50 mg/kg), WAY 100635 (1 mg/kg), and naloxone (1 mg/kg), respectively. The effect of aripiprazole was compared with 30 mg/kg pregabalin in the neuropathic pain model and 30 mg/kg duloxetine in the fibromyalgia model. Aripiprazole demonstrated significant antiallodynic and antihyperalgesic activity in both models. It did not change locomotor activity at a dose of 1 mg/kg but caused a decrease at a dose of 5 mg/kg. Dopamine D2, serotonin 5-HT1A, and opioidergic receptors contributed to aripiprazole's effects at varying levels. This study highlights the potential use of aripiprazole for managing neuropathic pain and fibromyalgia by targeting multiple receptor systems. The findings demonstrate the potential use of aripiprazole alone or as an adjuvant in the treatments of neuropathic pain and fibromyalgia.

The Role of Pain Medications in Modulating Peripheral Nerve Injury Recovery

Peripheral nerve injuries (PNIs) are common, costly, and cause significant pain. Effective management of PNIs involves tailoring medications to the injury type as well as understanding the pharmacokinetics/pharmacodynamics to support nerve regeneration and reduce pain. Opioids act on opioid receptors to significantly reduce pain for many patients, but there are significant addiction risks and side effects. In addition, opioids may exacerbate pain sensitivity and affect nerve regeneration. Non-steroidal anti-inflammatory drugs or acetaminophen act on cyclooxygenase enzymes and are commonly used for nerve pain, with 34.7% of people using them for neuropathic pain. While effective for mild pain, they are often combined with opioids, gamma-aminobutyric acid (GABA) analogs, lidocaine, or corticosteroids for more severe pain. Corticosteroids, mimicking adrenal hormones like cortisol, treat PNI-related inflammation and pain. Their pharmacokinetics are complex, often requiring local injections in order to minimize systemic risks while effectively treating PNIs. Lidocaine, a common local anesthetic, blocks ion channels in the central nervous system (CNS) and peripheral nerves, providing strong analgesic and anti-inflammatory effects. If used improperly, lidocaine can cause neuronal toxicity instead of anesthetic effect. GABA acts as an inhibitory neurotransmitter in the CNS and its drug analogs like pregabalin and gabapentin can alleviate neuropathic pain by binding to voltage-gated Ca2+ channels, inhibiting neurotransmitter release. These pain medications are commonly prescribed for PNIs despite a limited guidance on their effects on nerve regeneration. This review will discuss these drug's mechanisms of action, pharmacokinetics/pharmacodynamics, and their clinical application to highlight their effect on the PNI recovery.

Effectiveness and user experience of a virtual reality intervention in a cohort of patients with chronic musculoskeletal pain syndromes

Chronic musculoskeletal pain (CMP) syndromes, including fibromyalgia, present diverse physical and psychological symptoms often resistant to pharmacological treatment. To retrospectively evaluate the effectiveness and user experience of Virtual Reality (VR) in reducing pain and anxiety in CMP patients and identify predictors of positive response. Data from 91 CMP patients in a 2-week interdisciplinary pain program were analyzed (78% met fibromyalgia criteria). Pain and anxiety were assessed using Numerical Rating Scales (NRS 0-10) before and after VR. Follow-up interviews were conducted after one month. An unsupervised machine learning model explored response patterns. VR led to a moderate but significant short-term reduction in anxiety and pain (median NRS -1.0, p < 0.001). A reduction of ≥3 NRS points occurred in 25% (anxiety) and 14% (pain). High baseline anxiety (NRS ≥ 7) correlated with greater pain reduction (median -2.0, p = 0.01). After one month, half of the patients reported sustained benefits. Catastrophizing and benzodiazepine use were linked to improved anxiety outcomes. Machine learning identified a most responsive cluster, characterized by patients with nociplastic pain, alexithymia, and anxiety. VR provided moderate short- and mid-term benefits for anxiety and pain in CMP patients, particularly in those with nociplastic pain and high baseline anxiety.

Afobazole alleviates streptozotocin-induced diabetic nephropathy in rats via hypoglycemic, antioxidant, anti-inflammatory, and anti-apoptotic properties: Role of the S1R/Nrf2 antioxidant axis

AIMS

Sigma-1 receptor (S1R) activation was recently identified as a promising target for preventing diabetic nephropathy (DN) by mitigating hypoxia, oxidative stress, and inflammation. This study aimed to investigate the potential reno-protective effect of the S1R agonist afobazole against streptozotocin (STZ)-induced DN in rats compared to metformin.

MATERIALS AND METHODS

Rats were split into six groups: the normal control group; the diabetic control group received STZ (55 mg/kg i.p.); the other four groups received STZ and were treated with different doses of either afobazole (10, 15, and 20 mg/kg) or metformin (200 mg/kg). Metabolic parameters and renal function were assessed. Expression levels of oxidative stress markers and inflammatory cytokines were measured using ELISA, apoptosis-related proteins were evaluated using immunohistochemistry, and gene expression of S1R, Nrf2, NF-κB, and TLR-4 was determined. Histopathological analysis was performed on kidney tissues.

KEY FINDINGS

Both afobazole and metformin exerted hypoglycemic effects, alleviating renal injury, reducing blood urea nitrogen (BUN) and serum creatinine, and restoring oxidant/antioxidant balance in diabetic rats. Both treatments boosted renal S1R and Nrf2 levels, suppressed inflammatory proteins and cytokines, and reduced apoptotic features.

SIGNIFICANCE

The study revealed that afobazole provided nephroprotection in STZ-induced DN through a hypoglycemic, antioxidant, anti-inflammatory, and anti-apoptotic potential mediated by activating the S1R/Nrf2 antioxidant axis. The 15 mg/kg dose elicited the most pronounced nephroprotective effects, outperforming other treatment groups.

Peripheral inflammation enhances opioid-induced gastrointestinal motility inhibition via up-regulating spinal mu opioid receptor

Opioids are potent analgesics in clinical pain management but exert variable analgesia in different pain types. Opioid-induced constipation is a common side effect of opioid therapy, and whether opioids induce different gastrointestinal motility inhibitions in different pain types is unknown. In this study, we evaluated the antinociceptive effects and inhibition of upper gastrointestinal transit and colonic bead expulsion of morphine, DAMGO, and Deltorphin in mouse CFA chronic inflammatory pain, SNI chronic neuropathic pain, and carrageenan chronic inflammatory pain models. Furthermore, quantitative PCR and immunofluorescence were used to investigate the mechanisms underlying the altered inhibition. Results showed that intrathecal administration of morphine, DAMGO, and Deltorphin produced higher antinociceptive effects in the CFA and carrageenan groups than in the SNI group. Upper gastrointestinal transit inhibition was significantly enhanced in the carrageenan group by morphine and DAMGO; colonic bead expulsion inhibition was also enhanced in the CFA and carrageenan groups by morphine and DAMGO, but not in Deltorphin treatment. Additionally, mu (MOR) opioid receptor mRNA and MOR-expressing cell density in the lumbar spinal cord of CFA and carrageenan mice were increased, whereas delta opioid receptor expression remained unchanged in these groups. Finally, the pharmacological blockade of MOR completely prevented the enhanced upper gastrointestinal transit inhibition in the carrageenan group by morphine and DAMGO. Altogether, our results indicate that gastrointestinal motility inhibition induced by MOR agonists can be enhanced with upregulated spinal MOR expression in chronic inflammatory pain.

Nociplastic pain: controversy of the concept

Classically, pain can be of a nociceptive or neuropathic nature, which refers to non-neural or neural tissue lesions, respectively. Chronic pain in conditions such as migraine, fibromyalgia, and complex regional pain syndrome (CRPS), is thought to perpetuate without a noxious input. Pain in such patients can be assigned neither to the nociceptive nor neuropathic category. Therefore, a third pain descriptor, named "nociplastic pain", has been adopted by the International Association for the Study of Pain. The current controversy-focused narrative review updates littledebated aspects of the new pain concept. The most disputable feature of nociplastic pain is its autonomous persistence, i.e., existence without causative tissue damage, presumably because of a malfunction of pain pathways and processing. This contradicts the fact that nociplastic pain is accompanied by persistent central sensitization that has been shown to require a continuing noxious input, e.g ., nerve injury. Even if sensitization occurs without a lesion, e.g ., in psychogenic and emotional pain, peripheral stimulus is necessary to produce pain. A logical weakness of the concept is that the word "plastic" in biology refers to adaptation rather than to maladaptation. The pathophysiologic mechanism of nociplastic pain may, in fact, be associated with background conditions that elude diagnosis because of the limitations of current diagnostic means. Misapplication of the nociplastic pain category may weaken diagnostic alertness toward occult causes of pain. Possible diagnostic errors could be avoided by understanding that nociplastic pain is a mechanism of pain rather than a diagnosis. Clinical use of this pain descriptor deserves a wider critical discussion.

Virtual reality as a treatment for chronic musculoskeletal pain syndromes

Chronic musculoskeletal pain syndromes, including fibromyalgia, are often resistant to conventional medications and invasive therapies. Central hypersensitization, neurotransmitter dysregulation, and autonomic nervous system abnormalities are key pathomechanisms, frequently resulting in widespread pain and a variety of psychosomatic symptoms. Virtual Reality (VR) applications have demonstrated effectiveness in reducing pain, both during and after interventions, and in chronic conditions such as fibromyalgia and back pain. The proposed mechanisms behind VR's effectiveness include distraction and immersion, coupled with cognitive behavioral therapy, which promote neuroplasticity and alter pain perceptions. Functional MRI studies have shown the impact of VR interventions on specific brain regions. Advances in hardware and software, potentially combined with treatments like biofeedback, could enhance VR's role in managing chronic pain. Currently, VR for musculoskeletal pain syndromes is primarily used within multimodal programs, but it is also available for home use as a standalone health application. Future research should focus on the 'drug-like' effects of VR, requiring controlled trials with comparable study populations and appropriate sham interventions.

Repressing iron overload ameliorates central post-stroke pain via the Hdac2-Kv1.2 axis in a rat model of hemorrhagic stroke

JOURNAL/nrgr/04.03/01300535-202412000-00027/figure1/v/2024-04-08T165401Z/r/image-tiff Thalamic hemorrhage can lead to the development of central post-stroke pain. Changes in histone acetylation levels, which are regulated by histone deacetylases, affect the excitability of neurons surrounding the hemorrhagic area. However, the regulatory mechanism of histone deacetylases in central post-stroke pain remains unclear. Here, we show that iron overload leads to an increase in histone deacetylase 2 expression in damaged ventral posterolateral nucleus neurons. Inhibiting this increase restored histone H3 acetylation in the Kcna2 promoter region of the voltage-dependent potassium (Kv) channel subunit gene in a rat model of central post-stroke pain, thereby increasing Kcna2 expression and relieving central pain. However, in the absence of nerve injury, increasing histone deacetylase 2 expression decreased Kcna2 expression, decreased Kv current, increased the excitability of neurons in the ventral posterolateral nucleus area, and led to neuropathic pain symptoms. Moreover, treatment with the iron chelator deferiprone effectively reduced iron overload in the ventral posterolateral nucleus after intracerebral hemorrhage, reversed histone deacetylase 2 upregulation and Kv1.2 downregulation, and alleviated mechanical hypersensitivity in central post-stroke pain rats. These results suggest that histone deacetylase 2 upregulation and Kv1.2 downregulation, mediated by iron overload, are important factors in central post-stroke pain pathogenesis and could serve as new targets for central post-stroke pain treatment.

Semaglutide Ameliorates Diabetic Neuropathic Pain by Inhibiting Neuroinflammation in the Spinal Cord

Glucagon-like peptide 1 (GLP-1) receptor agonists are frequently used to treat type 2 diabetes and obesity. Despite the development of several drugs for neuropathic pain management, their poor efficacy, tolerance, addiction potential, and side effects limit their usage. Teneligliptin, a DPP-4 inhibitor, has been shown to reduce spinal astrocyte activation and neuropathic pain caused by partial sciatic nerve transection. Additionally, we showed its capacity to improve the analgesic effects of morphine and reduce analgesic tolerance. Recent studies indicate that GLP-1 synthesized in the brain activates GLP-1 receptor signaling pathways, essential for neuroprotection and anti-inflammatory effects. Multiple in vitro and in vivo studies using preclinical models of neurodegenerative disorders have shown the anti-inflammatory properties associated with glucagon-like peptide-1 receptor (GLP-1R) activation. This study aimed to investigate the mechanism of antinociception and the effects of the GLP-1 agonist semaglutide (SEMA) on diabetic neuropathic pain in diabetic rats.

METHODS

Male Wistar rats, each weighing between 300 and 350 g, were categorized into four groups: one non-diabetic sham group and three diabetic groups. The diabetic group received a single intraperitoneal injection of streptozotocin (STZ) at a dosage of 60 mg/kg to induce diabetic neuropathy. After 4 weeks of STZ injection, one diabetic group was given saline (vehicle), and the other two were treated with either 1× SEMA (1.44 mg/kg, orally) or 2× SEMA (2.88 mg/kg, orally). Following a 4-week course of oral drug treatment, behavioral, biochemical, and immunohistochemical analyses were carried out. The mechanical allodynia, thermal hyperalgesia, blood glucose, advanced glycation end products (AGEs), plasma HbA1C, and spinal inflammatory markers were evaluated.

RESULTS

SEMA treatment significantly reduced both allodynia and hyperalgesia in the diabetic group. SEMA therapy had a limited impact on body weight restoration and blood glucose reduction. In diabetic rats, SEMA lowered the amounts of pro-inflammatory cytokines in the spinal cord and dorsal horn. It also lowered the activation of microglia and astrocytes in the dorsal horn. SEMA significantly reduced HbA1c and AGE levels in diabetic rats compared to the sham control group.

CONCLUSIONS

These results indicate SEMA's neuroprotective benefits against diabetic neuropathic pain, most likely by reducing inflammation and oxidative stress by inhibiting astrocyte and microglial activity. Our findings suggest that we can repurpose GLP-1 agonists as potent anti-hyperalgesic and anti-inflammatory drugs to treat neuropathic pain without serious side effects.

Targeted therapy: P2X3 receptor silencing in bone cancer pain relief

Bone cancer pain remains a significant clinical challenge, often refractory to conventional treatments. The upregulation of the P2X3 receptor in the dorsal root ganglia has been implicated in the pathogenesis of bone cancer pain. This study aimed to elucidate the role of the P2X3 receptor in this context and assess the therapeutic potential of receptor silencing. Utilizing a rat model with Walker 256 cells to simulate bone cancer pain, researchers conducted molecular analyses, including semi-quantitative RT-PCR and Western Blot, to investigate P2X3 receptor expression in the dorsal root ganglia. Results demonstrated a marked increase in P2X3 receptor levels in the dorsal root ganglia of the bone cancer pain model. Targeted silencing of the P2X3 receptor using specific shRNA delivered via lentiviral vectors significantly reduced pain sensitivity, underscoring the receptor's potential as a valuable therapeutic target. In addition, a comprehensive gene expression analysis leveraging the GEO data set GSE249443 was performed to explore the underlying biological pathways linked to bone cancer pain. This analysis provided insights into the intricate interplay between bone cancer pain and associated biological processes, offering a deeper understanding of the mechanisms involved in pain modulation and progression. In conclusion, this research identifies the P2X3 receptor as a critical molecular target for mitigating bone cancer pain. The selective silencing of the P2X3 receptor emerges as a promising and innovative therapeutic strategy, presenting novel avenues for managing bone cancer pain and potentially revolutionizing treatment approaches in this challenging domain.

Analysis of single-cell transcriptome data from a mouse model implicates protein synthesis dysfunction in schizophrenia

BACKGROUND

Schizophrenia is a mental disorder that causes considerable morbidity, whose risk largely results from genetic factors. Setd1a is a gene implicated in schizophrenia.

OBJECTIVE

To study the gene expression changes found in heterozygous Setd1a± knockout mice in order to gain useful insight into schizophrenia pathogenesis.

METHODS

We mined a single-cell RNA sequencing (scRNAseq) dataset from the prefrontal cortex (PFC) and striatum of Setd1a± mice and identified cell type-specific differentially expressed genes (DEGs) and differential transcript usage (DTU). DEGs and genes containing DTU found in each cell type were used to identify affected biological pathways using Ingenuity Pathway Analysis (IPA).

RESULTS

We identified 273 unique DEGs across all cell types in PFC and 675 unique gene peaks containing DTU. In striatum, we identified 327 unique DEGs across all cell types and 8 unique gene peaks containing DTU. Key IPA findings from the analysis of DEGs found in PFC and striatum implicate processes involved in protein synthesis, mitochondrial function, cell metabolism, and inflammation. IPA analysis of genes containing DTU in PFC points to protein synthesis, as well as cellular activities involving intracellular signaling and neurotransmission. One canonical pathway, 'EIF2 Signaling', which is involved in the regulation of protein synthesis, was detected in PFC DEGs, striatum DEGs, and PFC genes containing DTU, drawing attention to its importance in schizophrenia pathophysiology.

CONCLUSION

Processes involving protein synthesis in general and the 'EIF2 Signaling' pathway in particular could be targets for the development of new research strategies and biomarkers in schizophrenia.

A New Application for Cenicriviroc, a Dual CCR2/CCR5 Antagonist, in the Treatment of Painful Diabetic Neuropathy in a Mouse Model

The ligands of chemokine receptors 2 and 5 (CCR2 and CCR5, respectively) are associated with the pathomechanism of neuropathic pain development, but their role in painful diabetic neuropathy remains unclear. Therefore, the aim of our study was to examine the function of these factors in the hypersensitivity accompanying diabetes. Additionally, we analyzed the analgesic effect of cenicriviroc (CVC), a dual CCR2/CCR5 antagonist, and its influence on the effectiveness of morphine. An increasing number of experimental studies have shown that targeting more than one molecular target is advantageous compared with the coadministration of individual pharmacophores in terms of their analgesic effect. The advantage of using bifunctional compounds is that they gain simultaneous access to two receptors at the same dose, positively affecting their pharmacokinetics and pharmacodynamics and consequently leading to improved analgesia. Experiments were performed on male and female Swiss albino mice with a streptozotocin (STZ, 200 mg/kg, i.p.) model of diabetic neuropathy. We found that the blood glucose level increased, and the mechanical and thermal hypersensitivity developed on the 7th day after STZ administration. In male mice, we observed increased mRNA levels of Ccl2, Ccl5, and Ccl7, while in female mice, we observed additional increases in Ccl8 and Ccl12 levels. We have demonstrated for the first time that a single administration of cenicriviroc relieves pain to a similar extent in male and female mice. Moreover, repeated coadministration of cenicriviroc with morphine delays the development of opioid tolerance, while the best and longest-lasting analgesic effect is achieved by repeated administration of cenicriviroc alone, which reduces pain hypersensitivity in STZ-exposed mice, and unlike morphine, no tolerance to the analgesic effects of CVC is observed until Day 15 of treatment. Based on these results, we suggest that targeting CCR2 and CCR5 with CVC is a potent therapeutic option for novel pain treatments in diabetic neuropathy patients.

The interplay between the microbiota and opioid in the treatment of neuropathic pain

Neuropathic pain (NP) is characterized by its complex and multifactorial nature and limited responses to opioid therapy; NP is associated with risks of drug resistance, addiction, difficulty in treatment cessation, and psychological disorders. Emerging research on gut microbiota and their metabolites has demonstrated their effectiveness in alleviating NP and augmenting opioid-based pain management, concurrently mitigating the adverse effects of opioids. This review addresses the following key points: (1) the current advances in gut microbiota research and the challenges in using opioids to treat NP, (2) the reciprocal effects and benefits of gut microbiota on NP, and (3) the interaction between opioids with gut microbiota, as well as the benefits of gut microbiota in opioid-based treatment of NP. Through various intricate mechanisms, gut microbiota influences the onset and progression of NP, ultimately enhancing the efficacy of opioids in the management of NP. These insights pave the way for further pragmatic clinical research, ultimately enhancing the efficacy of opioid-based pain management.

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.

Neuromodulation and Habituation: A Literature Review and Conceptional Analysis of Sustaining Therapeutic Efficacy and Mitigating Habituation

Spinal cord stimulation (SCS) is a therapeutic modality for the treatment of various chronic pain conditions that has rapidly evolved over the past 50 years. Unfortunately, over time, patients implanted with SCS undergo a habituation phenomenon leading to decreased pain relief. Consequently, the discovery of new stimulation waveforms and SCS applications has been shown to prolong efficacy and reduce explantation rates. This article explores various SCS waveforms, their applications, and proposes a graded approach to habituation mitigation. We suspect the neural habituation phenomenon parallels that seen in pharmacology. Consequently, we urge further exploration of the early introduction of these stimulation strategies to abate spinal cord stimulation habituation.

Complex Hippocampal Response to Thermal Skin Injury and Protocols with Hyperbaric Oxygen Therapy and Filipendula ulmaria Extract in Rats

The aim of this study was to evaluate the alterations of the hippocampal function that may be related to anxiogenic response to thermal skin injury, including the morpho-functional alterations, and the effects of hyperbaric oxygen (HBO) and Filipendula ulmaria (FU) extract in the treatment of anxiety-like behavior that coincides with thermal skin injury. A rat thermal skin injury experimental model was performed on 2-month-old male Wistar albino rats. The evaluated therapeutic protocols included HBO and/or antioxidant supplementation. HBO was applied for 7 days in the hyperbaric chamber (100% O2, 2.5 ATA, 60 min). Oral administration of FU extract (final concentration of 100 mg/kg b.w.) to achieve antioxidant supplementation was also applied for 7 days. Anxiety level was estimated in the open field and elevated plus-maze test, which was followed by anesthesia, sacrifice, and collection of hippocampal tissue samples. HBO treatment and FU supplementation significantly abolished anxiogenic response to thermal skin injury. This beneficial effect was accompanied by the reduction in hippocampal pro-inflammatory and pro-apoptotic indicators, and enhanced BDNF and GABA-ARα2S gene expression, previously observed in untreated burns. The hippocampal relative gene expression of melatonin receptors and NPY positively responded to the applied protocols, in the same manner as µ and δ opioid receptors, while the opposite response was observed for κ receptors. The results of this study provide some confirmations that adjuvant strategies, such as HBO and antioxidant supplementation, may be simultaneously applied in the treatment of the anxiety-like behavior that coincides with thermal skin injury.

Technical guideline for intra-prepontine cisternal drug delivery via spinal puncture through subarachnoid catheterization

OBJECTIVES

The distribution characteristics of intrathecal drugs and the limitation of current catheterization techniques make traditional intrathecal analgesic treatment nearly useless for refractory craniofacial pain, such as trigemina neuralgia. This technical guideline aims to promote the widespread and standardize the application of intra-prepontine cisternal drug delivery via spinal puncture and catheterization.

METHODS

A modified Delphi approach was used to work for this guideline. On the issues related to the intra-prepontine cisternal targeted drug delivery technique, the working group consulted 10 experts from the field with 3 rounds of email feedback and 3 rounds of conference discussion.

RESULTS

For the efficacy and safety of the intra-prepontine cisternal targeted drug delivery technique, a consensus was formed on 7 topics (with an agreement rate of more than 80%), including the principles of the technique, indications and contraindications, patient preparation, surgical specifications for intra-prepontine cisternal catheter placement, analgesic dosage coordination, analgesic management, and prevention and treatment of complications.

CONCLUSIONS

Utilizing the intra-prepontine cisternal drug infusion system to manage refractory craniofacial pain could provide advantages in terms of minimally invasive, secure, and effective treatment. This application can not only alleviate the suffering of individuals experiencing the prolonged pain but also support the maintenance of quality of life and dignity in their final moments, justifiing its widespread dissemination and standardized adoption in domestic and international professional fields.

The Roles of Endogenous D2R Dopamine and μ-opioid Receptors of the Brain in Alcohol use Disorder

Alcohol use disorder (AUD) affects millions of people worldwide. It is characterized by a strong physiological and psychological craving to consume large amounts of alcohol despite adverse consequences. Alcohol use disorder carries a large health and economic burden on society. Despite its prevalence, AUD is still severely undertreated. The precise molecular mechanisms of how alcohol addiction forms are yet unknown. However, previous studies on animal models show that along with the μ-opioid receptors, the D2R dopamine receptors may also be involved in alcohol craving and reward pathways. Currently, there is a limited number of treatment strategies for alcohol use disorder, which include several medications and therapy. By understanding the limitations of current treatment options and exploring new potential targets, it could be possible to find more effective ways of treating AUD in the future.

Simultaneous Administration of Hyperbaric Oxygen Therapy and Antioxidant Supplementation with Filipendula ulmaria Extract in the Treatment of Thermal Skin Injuries Alters Nociceptive Signalling and Wound Healing

Background and Objectives: Thermal skin injuries are a prevalent cause of skin damage, potentially leading to severe morbidity and significant mortality. In this study, we intended to estimate the effects of HBO (hyperbaric oxygen treatment) and antioxidant supplementation with Filipendula ulmaria extract, individually and simultaneously, in the treatment of thermal skin injuries. Materials and Methods: As a thermal skin injury experimental model, we used two-month-old male Wistar albino rats. Thermal injuries were made with a solid aluminium bar at a constant temperature of 75 °C for 15 s. Hyperbaric oxygen treatment was performed in a specially constructed hyperbaric chamber for rats (HYB-C 300) for seven consecutive days (100% O2 at 2.5 ATA for 60 min). Antioxidant supplementation was performed with oral administration of Filipendula ulmaria extract dissolved in tap water to reach a final concentration of 100 mg/kg b.w. for seven consecutive days. Results: Simultaneous administration of hyperbaric oxygen therapy and antioxidant supplementation with Filipendula ulmaria extract significantly ameliorated the macroscopic and histopathological characteristics of the wound area and healing. Also, this therapeutic approach decreased the local expression of genes for proinflammatory mediators and increased the expression of the μ-opioid receptor and the MT1 and MT2 receptors in the wound area and spinal cord, with a consequent increase in reaction times in behavioural testing. Conclusions: In conclusion, the presented results of our study allow evidence for the advantages of the simultaneous employment of HBO and antioxidant supplementation in the treatment of thermal skin injuries, with special reference to the attenuation of painful sensations accompanied by this type of trauma.

Teneligliptin Co-Infusion Alleviates Morphine Tolerance by Inhibition of Spinal Microglial Cell Activation in Streptozotocin-Induced Diabetic Rats

Morphine (MOR) is a commonly prescribed drug for the treatment of moderate to severe diabetic neuropathic pain (DNP). However, long-term MOR treatment is limited by morphine analgesic tolerance (MAT). The activation of microglial cells and the release of glia-derived proinflammatory cytokines are known to play an important role in the development of MAT. In this study, we aimed to investigate the effects of the dipeptidyl peptidase-4 inhibitor (DPP-4i) teneligliptin (TEN) on MOR-induced microglial cell activation and MAT in DNP rats. DNP was induced in four groups of male Wistar rats through a single intraperitoneal injection of streptozotocin (STZ) (50 mg/kg, freshly dissolved in 5 mmol/L citrate buffer, pH 4.5). Sham rats were administered with the vehicle. Seven days after STZ injection, all rats were implanted with an intrathecal (i.t) catheter connected to a mini-osmotic pump, divided into five groups, and infused with the following combinations: sham + saline (1 µL/h, i.t), DNP + saline (1 µL/h, i.t), DNP + MOR (15 µg/h, i.t), DNP + TEN (2 µg/h, i.t), and DNP + MOR (15 µg/h, i.t) + TEN (2 µg/h, i.t) for 7 days at a rate of 1 μL/h. The MAT was confirmed through the measurement of mechanical paw withdrawal threshold and tail-flick tests. The mRNA expression of neuroprotective proteins nuclear factor erythroid 2-related factor (Nrf2) and heme oxygenase-1 (HO-1) in the dorsal horn was evaluated by quantitative PCR (qPCR). Microglial cell activation and mononucleate cell infiltration in the spinal cord dorsal horn were assessed by immunofluorescence assay (IFA) and Western blotting (WB). The results showed that co-infusion of TEN with MOR significantly attenuated MAT in DNP rats through the restoration of neuroprotective proteins Nrf2 and HO-1 and suppression of microglial cell activation in the dorsal horn. Though TEN at a dose of 2 μg has mild antinociceptive effects, it is highly effective in limiting MAT.

Novel Drug Targets and Emerging Pharmacotherapies in Neuropathic Pain

Neuropathic pain is a debilitating condition characterized by abnormal signaling within the nervous system, resulting in persistent and often intense sensations of pain. It can arise from various causes, including traumatic nerve injury, neuropathy, and certain diseases. We present an overview of current and emerging pharmacotherapies for neuropathic pain, focusing on novel drug targets and potential therapeutic agents. Current pharmacotherapies, including tricyclic antidepressants, gabapentinoids, and serotonin norepinephrine re-uptake inhibitors, are discussed, as are emerging treatments, such as ambroxol, cannabidiol, and N-acetyl-L-cysteine. Additionally, the article highlights the need for further research in this field to identify new targets and develop more effective and targeted therapies for neuropathic pain management.