Gabapentin improves neuropathic pain in Minamata disease model rats.

BACKGROUND: Methylmercury (MeHg), the causative agent of Minamata disease, damages the cranial nervous system and causes specific sensory disturbances, especially hypoesthesia, in the extremities. However, recent reports demonstrate that patients with chronic Minamata disease conversely develop neuropathic pain in the lower extremities. Studies on our established Minamata disease model rats showed that MeHg-mediated neurodegeneration might induce neuropathic pain by over time through inducing rewiring with neuronal activation in the somatosensory cortex via microglial activation in the spinal dorsal horn. METHODS: In this study, the effects of gabapentin, a potentially effective treatment for neuropathic pain, was evaluated using this Minamata disease model rats. To further elucidate the mechanism of its medicinal effects, histochemical and biochemical analyses of the nervous system of Minamata disease model rats were conducted. RESULTS: Gabapentin treatment restored the reduction in the pain threshold caused by MeHg exposure in rats. Histochemical and biochemical analyses revealed that gabapentin showed no effect on MeHg-induced neurodegeneration in entire nervous system and microglial activation in the spinal dorsal horn. However, it was shown that gabapentin may reduce excessive synaptogenesis through its antagonist action on the alpha2-delta-1 subunit of calcium channels in the somatosensory cortex. CONCLUSIONS: These results indicate that gabapentin may alleviated neuropathic pain in MeHg poisoning, as typified by Minamata disease, by reversibly modulation synaptic rewiring in the somatosensory cortex.

Pyrazoles as Anti-inflammatory and Analgesic Agents: In-vivo and In-silico Studies.

BACKGROUND: Pyrazole is a well-known nucleus in the pharmacy field with a wide range of other activities in addition to anti-inflammatory and analgesic, i.e., anticonvulsant, antiviral, and anticancer activities. There are well-known marketed drugs having pyrazole moiety as celecoxib, and lonazolac as COX-II inhibitors. AIMS: We aim to synthesize better anti-inflammatory than existing ones. Thiophene is also known for its analgesic and anti-inflammatory action. Thus, the fusion of both gives better anti-inflammatory agents. In the present studies, derivatives from two series of pyrazole were prepared by reacting substituted chalcone (3a-3f) derivatives prepared from 2-acetyl thiophene. They substituted aromatic aldehydes with phenyl hydrazine to form (5a-5f) and with 2, 4-dinitro phenyl hydrazine giving compounds (6a-6f) separately. METHODS: Purified and characterized pyrazoles have been analyzed for in-vivo analgesic and anti-inflammatory activities by using standard methods. Compounds 5e, 5f, and 6d were proved to be potent analgesics and series (5a-5f) was found to have anti-inflammatory action, which was further validated using docking and ADME studies. RESULTS: The ADME profile of synthesized compounds was found to be satisfactory. CONCLUSION: The synthesized compounds can serve as lead for further drug designing.

Alleviating severity of limb trauma pain with coadministration of topical sesame oil and standard treatments: A GRADE-assessed systematic review and meta-analysis of randomised controlled trials.

Recent randomised controlled trials (RCTs) have investigated the analgesic activity of sesame oil among patients with limb trauma; nevertheless, their findings are inconsistent. Hence, this review aimed to clarify the impact of topical administration of sesame oil on acute pain of adult outpatients with minor limb trauma. The online databases (e.g., Scopus, PubMed, Web of Science) were searched up to 31 January 2024. The RCTs were included if they compared the effect of applying standard treatments plus topical sesame oil to administering standard treatments alone or with a placebo/sham treatment. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) and the Cochrane Collaboration's risk of bias tool were applied to address the evidence quality and the study's methodological rigour, respectively. Four RCTs had the inclusion criteria, and their findings were pooled in a meta-analysis employing a random-effects approach. According to the pooled analysis, the reduction in mean change of the pain score from baseline to the second/third intervention day was significantly higher in favour of clients who received standard care plus daily massage of the trauma site with sesame oil compared to those who received a control condition (weighted mean difference: -1.10; 95% confidence interval [-1.62, -0.57]; p < 0.001). However, the evidence quality was moderate, and only two studies had good methodological rigour. Hence, more high-quality studies are needed to make a solid evidence-based conclusion about the favourable consequence of topical sesame oil on alleviating acute traumatic limb pain.

[A case of chronic bromide intoxication due to continuous use of a commercially available analgesic in a patient diagnosed with pseudohyperchloremia].

An 87-year-old woman was admitted to our hospital with general fatigue, anorexia, nausea, and chest pain, and was diagnosed with Takotsubo cardiomyopathy and a stomal ulcer. Pseudohyperchloremia and a negative anion gap were detected in laboratory tests. She was continuously taking commercially available analgesics, including bromvalerylurea. On the 11th day of hospitalization, her bromide concentration was high (331.2 mg/L). She was readmitted with fatigue and anorexia one and a half years after her last hospitalization. On admission, her serum chloride and bromide levels were also high. Despite being instructed to stop taking analgesics after the first hospitalization, she was unable to stop taking the medication. It took more than two years for her blood bromide concentration to decrease and the withdrawal of the medication to be confirmed. Clinicians should consider bromide intoxication in patients with unclear neuropsychiatric symptoms and high chloride levels.

Linalyl acetate exerts analgesic effects by inhibiting nociceptive TRPA1 in mice.

Clary sage essential oil (CSEO) is utilized in perfumery, aromatherapy, and skincare. Linalyl acetate (LA), a primary component of CSEO, possesses sedative, anxiolytic, and analgesic properties. However, the mechanism of its analgesic action is not clearly understood. Transient receptor potential ankyrin 1 (TRPA1) channel, a non-selective cation channel, is mainly expressed in sensory neurons and serves as a sensor of various irritants. In this study, we investigated the effects of LA on TRPA1 channel using heterologous expression system and isolated sensory neurons. To detect channel activity, we employed Ca2+ imaging and the whole-cell patch-clamp technique. The analgesic action of LA was measured in a pain-related behavioral mouse model. In cells that heterologously expressed TRPA1, LA diminished [Ca2+]i and current responses to allylisothiocyanate (AITC) and carvacrol: exogenous TRPA1 agonists, and the inhibitory effects were more pronounced for the former than for the latter. Moreover, LA suppressed [Ca2+] i and current responses to PGJ2: an endogenous TRPA1 agonist. Similar inhibitory actions were observed in native TRPA1 channels expressed in mouse sensory neurons. Furthermore, LA diminished PGJ2-induced nociceptive behaviors in mice. These findings suggest that analgesic effects of LA exert through inhibition of nociceptive TRPA1, making it a potential candidate for novel analgesic development.

Improving door-to-analgesia timing in musculoskeletal injuries in an academic emergency department in India: a quality improvement project.

INTRODUCTION: Pain, more frequently due to musculoskeletal injuries, is a prevalent concern in emergency departments (EDs). Timely analgesic administration is paramount in the acute setting of ED. Despite its importance, many EDs face challenges in pain management and present opportunities for improvement. This initiative aimed to expedite the administration of the first analgesic in patients with musculoskeletal pain in the ED. LOCAL PROBLEM: Observations within our ED revealed that patients with musculoskeletal injuries triaged to yellow or green areas experienced prolonged waiting times, leading to delayed analgesic administration, thereby adversely affecting clinical care and patient satisfaction. SPECIFIC AIM: The aim of our quality improvement (QI) project was to reduce the time to administration of first analgesia by 30% from baseline, in patients with musculoskeletal injuries presenting to our academic ED, in a period of 8 weeks after the baseline phase. METHODS: A multidisciplinary QI team systematically applied Point-of-Care Quality Improvement and Plan-Do-Study-Act (PDSA) cycle methodologies. Process mapping and fishbone analyses identified the challenges in analgesia administration. Targeted interventions were iteratively refined through PDSA cycles. INTERVENTIONS: Interventions such as pain score documentation at triage, fast-tracking of patients with moderate-to-severe pain, resident awareness sessions, a pain management protocol and prescription audits were executed during the PDSA cycles. Successful elements were reinforced and adjustments were made to address the identified challenges. RESULTS: The median door-to-analgesia timing during the baseline phase was 55.5 min (IQR, 25.75-108 min). During the postintervention phase, the median was significantly reduced to 15 min (IQR, 5-37 min), exceeding the anticipated outcomes and indicating a substantial 73% reduction (p value <0.001) from baseline. CONCLUSION: Implementing simple change ideas resulted in a substantial improvement in door-to-analgesia timing within the ED. These findings significantly contribute to ongoing discussions on the optimisation of pain management in emergency care.

Turning down the body heat: A novel mechanism for TRPV1 antagonist-induced hyperthermia.

While effective analgesics, TRPV1 antagonists can dangerously alter thermoregulation. In this issue of Neuron, Huang et al.1 demonstrate that interaction with the S4-S5 linker of TRPV1 determines whether an antagonist affects core body temperature, with promising implications for analgesic development.

Use of electronic health record data to examine administrations of pro re nata analgesics during hip fracture post-acute care.

PURPOSE: Medications prescribed to older adults in US skilled nursing facilities (SNF) and administrations of pro re nata (PRN) "as needed" medications are unobservable in Medicare insurance claims. There is an ongoing deficit in our understanding of medication use during post-acute care. Using SNF electronic health record (EHR) datasets, including medication orders and barcode medication administration records, we described patterns of PRN analgesic prescribing and administrations among SNF residents with hip fracture. METHODS: Eligible participants resided in SNFs owned by 11 chains, had a diagnosis of hip fracture between January 1, 2018 to August 2, 2021, and received at least one administration of an analgesic medication in the 100 days after the hip fracture. We described the scheduling of analgesics, the proportion of available PRN doses administered, and the proportion of days with at least one PRN analgesic administration. RESULTS: Among 24 038 residents, 57.3% had orders for PRN acetaminophen, 67.4% PRN opioids, 4.2% PRN non-steroidal anti-inflammatory drugs, and 18.6% PRN combination products. The median proportion of available PRN doses administered per drug was 3%-50% and the median proportion of days where one or more doses of an ordered PRN analgesic was administered was 25%-75%. Results differed by analgesic class and the number of administrations ordered per day. CONCLUSIONS: EHRs can be leveraged to ascertain precise analgesic exposures during SNF stays. Future pharmacoepidemiology studies should consider linking SNF EHRs to insurance claims to construct a longitudinal history of medication use and healthcare utilization prior to and during episodes of SNF care.

Thoracotomy Patients Under General Anesthesia: A Comparison on Intra-Operative Anesthetic and Analgesic Requirements, When Combined with Either Epidural Analgesia or Continuous Unilateral Paravertebral Analgesia.

BACKGROUND AND OBJECTIVE: Regional analgesia is effective for post-thoracotomy pain. The primary objective of the study is to compare the intraoperative requirement of isoflurane and fentanyl between general anaesthesia (GA) with epidural analgesia and GA with paravertebral analgesia. METHODS AND MATERIAL: A prospective observational comparative study was conducted on 56 patients undergoing open thoracotomy procedures. The patients were divided into two groups of 28 by assigning the study participants alternatively to each group: Group GAE - received thoracic epidural catheterization with GA, and Group GAP - received ultrasound guided thoracic paravertebral catheterization on the operative side with GA. Intraoperative requirement of isoflurane, fentanyl, postoperative analgesia, stress response, need of rescue analgesics and adverse effects were observed and analysed. RESULTS: 25 patients in each group were included in the data analysis. The intraoperative requirement of isoflurane (32.28 ± 1.88 vs 48.31 ± 4.34 ml; p < 0.0001) and fentanyl (128.87 ± 25.12 vs 157 ± 30.92 µg; p = 0.0009) were significantly less in the GAE group than in the GAP group. VAS scores and need of rescue analgesics and blood glucose levels were not statistically significant during the postoperative period (p > 0.05). The incidence of adverse effects was comparable except for hypotension and urinary retention which were significantly higher in the GAE group. CONCLUSION: GA with epidural analgesia resulted in significant reduction in the intraoperative consumption of isoflurane and fentanyl in comparison to GA with paravertebral analgesia. However, both the techniques were equally effective in the postoperative period.

Utilizing experimental design and desirability function in optimizing RP-HPLC method for simultaneous determination of some skeletal muscle relaxants and analgesics.

An experimental design and response surface methodologies using Plackett-Burman and Box-Behnken designs were applied for selecting and optimizing the most appropriate parameters which significantly affect the separation and quantitative estimation of five skeletal muscle relaxants and four analgesic drugs (baclofen, methocarbamol, dantrolene sodium, orphenadrine citrate, cyclobenzaprine hydrochloride, ketoprofen, etoricoxib, ibuprofen, and mefenamic acid) with a relatively short duration of analysis in a single run. For the separation of the nine drugs, an INERTSIL ODS-V3-5 µm C18 column (250 × 4.6 mm I.D.) was used with the optimum mobile phase conditions (45.15 mM ammonium acetate buffer pH 5.56 adjusted with acetic acid, acetonitrile, and methanol in a ratio of 30.5:29.5:40, v/v/v with a flow rate of 1.5 mL/min) and UV-detection at 220 nm. The optimized method was successfully subjected to the validation steps as described in ICH guidelines for linearity, precision, accuracy, robustness, and sensitivity. The optimized and validated method was effectively applied to determine the content of the studied drugs in their pharmaceutical preparations and to expand its applicability to the counterfeit estimation of etoricoxib in different brands of tablet dosage forms.

Evaluation of the effects of pregabalin and dexamethasone coadministration on preemptive multimodal analgesia and anxiety in third molar surgeries: a triple-blind randomized clinical trial.

OBJECTIVE: To evaluate the efficacy of pregabalin and dexamethasone coadministration in preemptive analgesia and anxiety control in lower third molar surgery. MATERIALS AND METHODS: A triple-blind, split-mouth clinical trial conducted with patients divided into two groups: control group, receiving placebo and dexamethasone, and test group, receiving pregabalin and dexamethasone preoperatively. The evaluated variables were pain, measured by the Visual Analog Scale (VAS), anxiety assessed through the State-Trait Anxiety Inventory (STAI) questionnaires, hemodynamic parameters [Blood Pressure (BP), Heart Rate (HR), Oxygen Saturation (SpO2)], and sedation assessed by the Ramsay scale. RESULTS: A total of 31 patients were included. The test group exhibited a significant reduction in pain at 2,4,6,8,12,16,24, and 48 h after surgery and in the consumption of rescue analgesics. Anxiety, evaluated by STAI and VAS, showed a significant decrease in the test group (p < 0.001). Additionally, there was a significant decrease in BP at most of the assessed time points (p < 0.05) and a significant reduction in HR at two different time intervals (p = 0.003 and p = 0.009), indicating a positive effect in the test group. There was no significant difference in SpO2 between the groups. Sedation assessment revealed a significant difference at all time points favoring the test group (p < 0.05). There were no significant postoperative adverse effects. CONCLUSIONS: Pregabalin coadministered with dexamethasone demonstrated significant efficacy in controlling postoperative pain and anxiety, as well as a sedative effect. CLINICAL RELEVANCE: The coadministration of pregabalin with dexamethasone may presents potential advantages in both pain modulation and psychological well-being of individuals undergoing third molar surgeries. TRIAL REGISTRATION: Brazilian Clinical Trials Registry (REBEC), No. RBR-378h6t6.

The Analgesic Potential of Litsea Species: A Systematic Review.

Various plant species from the Litsea genus have been claimed to be beneficial for pain relief. The PRISMA approach was adopted to identify studies that reported analgesic properties of plants from the Litsea genus. Out of 450 records returned, 19 primary studies revealed the analgesic potential of nine Litsea species including (1) Litsea cubeba, (2) Litsea elliptibacea, (3) Litsea japonica, (4) Litsea glutinosa, (5) Litsea glaucescens, (6) Litsea guatemalensis, (7) Litsea lancifolia, (8) Litsea liyuyingi and (9) Litsea monopetala. Six of the species, 1, 3, 4, 7, 8 and 9, demonstrated peripheral antinociceptive properties as they inhibited acetic-acid-induced writhing in animal models. Species 1, 3, 4, 8 and 9 further showed effects via the central analgesic route at the spinal level by increasing the latencies of heat stimulated-nocifensive responses in the tail flick assay. The hot plate assay also revealed the efficacies of 4 and 9 at the supraspinal level. Species 6 was reported to ameliorate hyperalgesia induced via partial sciatic nerve ligation (PSNL). The antinociceptive effects of 1 and 3 were attributed to the regulatory effects of their bioactive compounds on inflammatory mediators. As for 2 and 5, their analgesic effect may be a result of their activity with the 5-hydroxytryptamine 1A receptor (5-HT1AR) which disrupted the pain-stimulating actions of 5-HT. Antinociceptive activities were documented for various major compounds of the Litsea plants. Overall, the findings suggested Litsea species as good sources of antinociceptive compounds that can be further developed to complement or substitute prescription drugs for pain management.

Analgesic and Psychotropic Effects of a New Bradykinin Antagonist.

A bradykinin B1 receptors antagonist PAV-0056, an 1,4-benzodiazepin-2-one derivative, intragastrically administrated to mice at doses of 0.1 and 1 mg/kg causes analgesia in the "formalin test" not inferior to that of diclofenac sodium (10 mg/kg) and tramadol (20 mg/kg). PAV-0056 at doses of 0.1 and 10 mg/kg has no anxiolytic and central muscle relaxant effects in mice and does not damage the gastric mucosa in rats. Based on the results of the conditioned place preference test, PAV-0056 also does not induce addiction in mice.

Mechanisms and Preventative Strategies for Persistent Pain following Knee and Hip Joint Replacement Surgery: A Narrative Review.

Chronic postsurgical pain (CPSP) following total knee arthroplasty (TKA) and total hip arthroplasty (THA) is a prevalent complication of joint replacement surgery which has the potential to decrease patient satisfaction, increase financial burden, and lead to long-term disability. The identification of risk factors for CPSP following TKA and THA is challenging but essential for targeted preventative therapy. Recent meta-analyses and individual studies highlight associations between elevated state anxiety, depression scores, preoperative pain, diabetes, sleep disturbances, and various other factors with an increased risk of CPSP, with differences observed in prevalence between TKA and THA. While the etiology of CPSP is not fully understood, several factors such as chronic inflammation and preoperative central sensitization have been identified. Other potential mechanisms include genetic factors (e.g., catechol-O-methyltransferase (COMT) and potassium inwardly rectifying channel subfamily J member 6 (KCNJ6) genes), lipid markers, and psychological risk factors (anxiety and depression). With regards to therapeutics and prevention, multimodal pharmacological analgesia, emphasizing nonopioid analgesics like acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs), has gained prominence over epidural analgesia. Nerve blocks and local infiltrative anesthesia have shown mixed results in preventing CPSP. Ketamine, an N-methyl-D-aspartate (NMDA)-receptor antagonist, exhibits antihyperalgesic properties, but its efficacy in reducing CPSP is inconclusive. Lidocaine, an amide-type local anesthetic, shows tentative positive effects on CPSP. Selective serotonin reuptake inhibitors (SSRIs) and serotonin norepinephrine reuptake inhibitors (SNRIs) have mixed results, while gabapentinoids, like gabapentin and pregabalin, present hopeful data but require further research, especially in the context of TKA and THA, to justify their use for CPSP prevention.

The Effect of Melatonin on Reducing the Frequency and Severity of Migraine Attacks: A Double-Blind, Randomized Clinical Trial.

Background: There is no definite recommendation for melatonin supplementation in episodic migraine. This study aimed to evaluate the effect of melatonin on reducing the frequency and severity of migraine attacks. Methods: This randomized, double-blind clinical trial was conducted at Golestan Hospital of Ahvaz, Iran, in 2021. A total of 60 patients with episodic migraine were randomly assigned into 2 groups of receiving 3 mg melatonin (intervention group; n=30) or the same dose of placebo (control group; n=30) along with baseline therapy (propranolol 20 mg, BID) for two months. The attack frequency, attack duration, attack severity (based on VAS), the number of analgesic intakes, drug complications, Migraine Disability Assessment score (MIDAS), and Pittsburgh sleep quality index (PSQI) were evaluated at baseline and in the first, second, third, and fourth months of follow-up. The independent t test, chi-square, and analysis of variance (ANOVA) with repeated measures were used to compare variables between the two groups. Results: In both groups, the frequency, duration, and severity of attacks, taking analgesics, MIDAS, and PSQI scores during follow-up decreased significantly (P<0.001). After treatment, the mean frequency (P=0.032) and duration of attacks (P=0.001), taking analgesic (P<0.001), and MIDAS (P<0.001) and PSQI scores (P<0.001) in the melatonin group were lower than placebo. Only the attack severity was not significantly different between the two groups (P=0.126). Side effects were observed in two patients (6.7%) in the melatonin group and one patient (3.3%) in the placebo group (P>0.999). Conclusion: Our study shows that melatonin was more efficacious than the placebo in the reduction of frequency and duration of migraine attacks. It was equally safe as the placebo and might be effective in the preventive treatment of episodic migraine in adults.Trial Registration Number: IRCT20190107042264N5.

Analgesia for the treatment of acute pancreatitis: a protocol for a systematic review and network meta-analysis.

INTRODUCTION: Gastrointestinal hospitalisations in the USA cause over US$130 billion in expenditures, and acute pancreatitis is a leading cause of these hospitalisations. Adequate pain control is one of the primary treatment goals for acute pancreatitis. Though opioids are commonly used for analgesia in these patients, there have been concerns about short-term and long-term side effects of using opioids. Recently, non-opioid medications have been studied to treat pain in patients with acute pancreatitis. This systematic review and network meta-analysis aims to assess the comparative efficacy of analgesic medication for non-severe, acute pancreatitis. METHODS AND ANALYSIS: We will search multiple electronic databases for randomised controlled trials that study pain management in patients with non-severe, acute pancreatitis. The intervention will be any analgesic for acute pancreatitis in the hospital setting. The comparison group will be patients who received a placebo or other active interventions for pain management. The primary outcomes of interest include pain scores and the need for supplementary analgesia. The secondary outcomes will be serious adverse events, local complications, progression to severe pancreatitis, transfer to the intensive care unit, length of hospitalisation, time to start enteral feeds, 30-day all-cause mortality and Quality of Life Scale scores. If sufficient homogeneity exists among included studies, the findings will be pooled using a traditional pairwise and network meta-analysis. The risk of bias in randomised control trials will be evaluated using the Cochrane Risk of Bias Tool 2.0. The Grading of Recommendations, Assessment, Development, and Evaluation approach will be used to report the certainty of evidence. ETHICS AND DISSEMINATION: This systematic review will not involve direct contact with human subjects. The findings of this review will be published in a peer-reviewed journal. They will give healthcare providers a better awareness of the optimal analgesic medication for pain treatment in non-severe, acute pancreatitis.

Transient receptor potential vanilloid 1 involved in the analgesic effects of total flavonoids extracted from Longxuejie ().

OBJECTIVE: To evaluate the analgesic effects of total flavonoids of Longxuejie (Resina Dracaenae Cochinchinensis) (TFDB) and explore the possible analgesic mechanism associated with transient receptor potential vanilloid 1 (TRPV1). METHODS: Whole-cell patch clamp technique was used to observe the effects of TFDB on capsaicin-induced TRPV1 currents. Rat experiments in vivo were used to observe the analgesic effects of TFDB. Western blot and immunofluorescence experiments were used to test the change of TRPV1 expression in DRG neurons induced by TFDB. RESULTS: Results showed that TFDB inhibited capsaicin-induced TRPV1 receptor currents in acutely isolated dorsal root ganglion (DRG) neurons of rats and the half inhibitory concentration was (16.7 ± 1.6) mg/L. TFDB (2-20 mg/kg) showed analgesic activity in the phase Ⅱ of formalin test and (0.02-2 mg per paw) reduced capsaicin-induced licking times of rats. TFDB (20 mg/kg) was fully efficacious on complete Freund's adjuvant (CFA)-induced inflammatory thermal hyperalgesia and capsaicin could weaken the analgesic effects. The level of TRPV1 expressions of DRG neurons was also decreased in TFDB-treated CFA-inflammatory pain rats. CONCLUSION: All these results indicated that the analgesic effect of TFDB may contribute to their modulations on both function and expression of TRPV1 channels in DRG neurons.

Analgesic effects of oral Yokukansan on acute postoperative pain and involvement of the serotonin nervous system: a mouse model study.

BACKGROUND: Yokukansan, a traditional Japanese medicine (Kampo), has been widely used to treat neurosis, dementia, and chronic pain. Previous in vitro studies have suggested that Yokukansan acts as a partial agonist of the 5-HT1A receptor, resulting in amelioration of chronic pain through inhibition of nociceptive neuronal activity. However, its effectiveness for treating postoperative pain remains unknown, although its analgesic mechanism of action has been suggested to involve serotonin and glutamatergic neurotransmission. This study aimed to investigate the effect of Yokukansan on postoperative pain in an animal model. METHODS: A mouse model of postoperative pain was created by plantar incision, and Yokukansan was administered orally the day after paw incision. Pain thresholds for mechanical and heat stimuli were examined in a behavioral experiment. In addition, to clarify the involvement of the serotonergic nervous system, we examined the analgesic effects of Yokukansan in mice that were serotonin-depleted by para-chlorophenylalanine (PCPA) treatment and intrathecal administration of NAN-190, 5-HT1A receptor antagonist. RESULTS: Orally administered Yokukansan increased the pain threshold dose-dependent in postoperative pain model mice. Pretreatment of para-chlorophenylalanine dramatically suppressed serotonin immunoreactivity in the spinal dorsal horn without changing the pain threshold after the paw incision. The analgesic effect of Yokukansan tended to be attenuated by para-chlorophenylalanine pretreatment and significantly attenuated by intrathecal administration of 2.5 µg of NAN-190 compared to that in postoperative pain model mice without para-chlorophenylalanine treatment and NAN-190 administration. CONCLUSION: This study demonstrated that oral administration of Yokukansan has acute analgesic effects in postoperative pain model mice. Behavioral experiments using serotonin-depleted mice and mice intrathecally administered with a 5-HT1A receptor antagonist suggested that Yokukansan acts as an agonist at the 5-HT1A receptor, one of the serotonin receptors, to produce analgesia.

Efficacy assessment of novel methanimine derivatives in chronic constriction injury-induced neuropathic model: An in-vivo, ex-vivo and In-Silico approach.

The multicomponent etiology, complex clinical implications, dose-based side effect and degree of pain mitigation associated with the current pharmacological therapy is incapable in complete resolution of chronic neuropathic pain patients which necessitates the perpetual requirement of novel medication therapy. Therefore, this study explored the ameliorative aptitude of two novel methanimine imitative like (E)-N-(4-nitrobenzylidene)-4­chloro-2-iodobenzamine (KB 09) and (E)-N-(4-methylbenzylidene)-4­chloro-2-iodobenzamine (KB 10) in chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain in rat model. Standard behavioral tests like dynamic and static allodynia, cold, thermal and mechanical hyperalgesia along with rotarod activity were performed at various experimental days like 0, 3, 7, 14 and 21. Enzyme linked immunosorbent assay (ELISA) on spinal tissue and antioxidant assays on sciatic nerve were executed accompanied by molecular docking and simulation studies. Prolonged ligation of sciatic nerve expressively induced hyperalgesia as well as allodynia in rats. KB 09 and KB 10 substantially attenuated the CCI elicited hyperalgesia and allodynia. They significantly reduced the biomarkers of pain and inflammation like Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in ELISA and while enhanced the GSH, SOD and CAT and diminished the MDA levels during antioxidant assays. KB 09 displayed -9.62 kcal/mol with TNF-α and -7.68 kcal/mol binding energy with IL-6 whereas KB 10 exhibited binding energy of -8.20 kcal/mol with IL-6 while -11.68 kcal/mol with TNF-α and hence both trial compounds ensured stable interaction with IL-6 and TNF-α during computational analysis. The results advocated that both methanimine derivatives might be novel candidates for attenuation of CCI-induced neuropathic pain prospects via anti-nociceptive, anti-inflammatory and antioxidant mechanisms.