Hot Plate Test Research Articles

New Pharmacological Insight into Etanercept and Pregabalin in Allodynia and Nociception: Behavioral Studies in a Murine Neuropathic Pain Model

Background/Objectives: Neuropathic pain is challenging to treat, often resistant to current therapies, and associated with significant side effects. Pregabalin, an anticonvulsant that modulates calcium channels, is effective but can impair mental and motor functions, especially in older patients. To improve patient outcomes, reducing the doses of pregabalin and combining it with other drugs targeting different neuropathic pain mechanisms may be beneficial. TNF-α blockers such as etanercept have shown potential in addressing neuropathic pain by affecting sodium channels, synaptic transmission, and neuroinflammation. This study evaluates the efficacy and safety of combining low doses of etanercept and pregabalin in allodynia and nociceptive tests. Materials and Methods: Male C57/BL6 mice underwent chronic constriction injury (CCI) of the sciatic nerve to induce neuropathic pain. They were divided into seven groups: sham control, CCI control, low and high doses of pregabalin, low and high doses of etanercept, and a combination of low doses of both drugs. Behavioral tests, including von Frey, hot-plate, and rotarod tests, were used to assess pain responses and motor activity. Results: The results indicated that a high dose of pregabalin significantly reduced mechanical allodynia and thermal hyperalgesia but impaired motor function. Conversely, low doses of etanercept alone had no significant effect. However, the combination of low doses of etanercept (20 mg/kg) and pregabalin (5 mg/kg) effectively alleviated pain without compromising locomotor activity. Conclusions: These results suggest a novel therapeutic strategy for neuropathic pain, enhancing analgesic efficacy while minimizing adverse effects.

Aprepitant mitigates paclitaxel-induced neuropathic pain in rats via suppressing inflammatory pathways in dorsal root ganglia

Neuropathic pain is the crucial dose-limiting side effect of paclitaxel in chemotherapy patients that negatively impacts the quality of life and survival. Currently, no effective treatment option is available. Aprepitant, a well-established chemotherapy antiemetic performing neurokinin-1 receptor antagonism, shows analgesic effects in some pain models. We studied aprepitant analgesic effects on the paclitaxel-induced neuropathic pain model in rats besides inflammatory markers assessment. Rats intraperitoneally received paclitaxel, reaching the cumulative paclitaxel dose of 8 mg/kg. Aprepitant was orally administered every alternate day between days 2 and 14, with a prescribed dosage of 10 or 20 mg/kg. The evaluation of mechanical allodynia and cold hyperalgesia involved the measurement of paw withdrawal threshold and acetone test score on days 0, 7, and 14. On day 14, paw licking latency was measured using a hot plate test before scarification and tissue collection for interleukin 1β, tumor necrosis factor α, and nuclear factor kappa B (NF-kB) evaluation. Paclitaxel induced neuropathy as indicated by a lowered hind paw withdrawal threshold in the Von Frey test, a higher score in the acetone test, and shortened hot plate latency. Aprepitant effectively alleviated cold and thermal hyperalgesia as well as mechanical allodynia. Moreover, aprepitant administration significantly reversed paclitaxel-mediated elevation of proinflammatory cytokines levels in dorsal root ganglia. In addition, aprepitant application suppressed the protein expression of NF-kB in the dorsal root ganglia of paclitaxel-treated rats, as revealed by western blot analysis. Aprepitant treatment ameliorates neuropathy induced by paclitaxel, which is associated with decreasing proinflammatory cytokines and NF-kB expression.

The deficient CLEC5A ameliorates the behavioral and pathological deficits via the microglial Aβ clearance in Alzheimer’s disease mouse model

BackgroundAlzheimer’s disease (AD) is a neurodegenerative disease that causes cognitive dysfunction in older adults. One of the AD pathological factors, β-Amyloid (Aβ), triggers inflammatory responses and phagocytosis of microglia. C-type lectin domain family 5 member A (CLEC5A) induces over-reactive inflammatory responses in several virus infections. Yet, the role of CLEC5A in AD progression remains unknown. This study aimed to elucidate the contribution of CLEC5A to Aβ-induced microglial activation and behavioral deficits.MethodsThe AD mouse model was crossed with Clec5a knockout mice for subsequent behavioral and pathological tests. The memory deficit was revealed by the Morris water maze, while the nociception abnormalities were examined by the von Frey filament and hotplate test. The Aβ deposition and microglia recruitment were identified by ELISA and immunohistochemistry. The inflammatory signals were identified by ELISA and western blotting. In the Clec5a knockdown microglial cell model and Clec5a knockout primary microglia, the microglial phagocytosis was revealed using the fluorescent-labeled Aβ.ResultsThe AD mice with Clec5a knockout improved Aβ-induced memory deficit and abnormal nociception. These mice have reduced Aβ deposition and increased microglia coverage surrounding the amyloid plaque, suggesting the involvement of CLEC5A in AD progression and Aβ clearance. Moreover, the phagocytosis was also increased in the Aβ-stressed Clec5a knockdown microglial cell lines and Clec5a knockout primary microglia.ConclusionThe Clec5a knockout ameliorates AD-like deficits by modulating microglial Aβ clearance. This study implies that targeting microglial Clec5a could offer a promising approach to mitigate AD progression.

Structure-Activity Relationship of 7-Chloro-4-(Phenylselanyl) Quinoline: Novel Antinociceptive and Anti-Inflammatory Effects in Mice.

The 7-chloro-4-(phenylselanyl)quinoline (4-PSQ) stands out for its potential antinociceptive and anti-inflammatory activities. Thus, in this study we investigated the structure-activity relationship of 4-PSQ and its analogues 7-chloro-4-[(4-fluorophenyl) selanyl]quinoline (a), 7-chloro-4-{[3-trifluoromethyl)phenyl] selanyl}quinoline (b), 4-((3,5-Bis(trifluoromethyl)phenyl)selanyl-7-chloroquinoline (c), 7-chloro-4-[(2,4,6-trimethyl)selanyl]quinolinic acid (d) and 7-chloroquinoline-4-selenium acid (e) in models of acute inflammation and chemical, thermal and mechanical nociception in mice, as well as by in silico methods. The compoundsa(-F),b(-CF3),c(-Bis-CF3),d(-CH3),e(-OOH) and 4-PSQ exert antinociceptive effects in chemical and thermal nociception models, except compoundsd(-CH3) ande(-OOH) that did not show antinociceptive effects in the hot plate test. In addition, treatments with all compounds did not cause locomotor changes in mice. In silico datathe compounds revealed that only compoundc(Bis-CF3) exhibited low gastrointestinal absorption and that compoundsc(Bis-CF3) ande(-OOH) do not have the ability to penetrate the blood-brain barrier, indicating that compounde(-OOH) did not produce a central antinociceptive effect. Furthermore, we found that this class of compounds has a higher affinity for COX-2 than for COX-1. In general, our data indicate that the insertion of substituents can alter the efficiency of 4-PSQ as an antinociceptive and anti-inflammatory agent.

Isolated during adolescence: long-term impact on social behavior, pain sensitivity, and the oxytocin system in male and female rats

BackgroundAdolescent social isolation (ASI) has profound long-term effects on behavioral and neural development. Despite this, the specific long-term impact of ASI during different adolescent stages and across sexes remain underexplored.MethodsOur study addresses this gap by examining the effects of early- and late- adolescent social isolation on both male and female rats. Rats were either isolated (or group-housed) starting from PD 21 (early) or PD 42 (late) for three weeks and then rehoused into groups. In adulthood (PD 90), rats underwent a battery of tests: elevated plus-maze, open field, novel object recognition, social interaction and social recognition memory and hotplate tests. Finally, we analyzed oxytocin receptor binding in several regions in the brains of a second cohort of rats.ResultsBoth, male and female rats from the late adolescent social isolation (LASI) groups spent significantly less time interacting in the social interaction test. Additionally, we observed a general decrease in social recognition memory regardless of sex. Both male ASI groups demonstrated heightened thermal pain sensitivity, while the opposite was observed in early adolescent social isolation (EASI) female rats. In the brain, we observed changes in oxytocin receptor (OTR) binding in the paraventricular nucleus of the hypothalamus (PVN) and paraventricular nucleus of the thalamus (PVT) and central amygdala (CeA) with the largest changes in EASI and LASI female rats.ConclusionOur model demonstrates long-lasting alterations on behavior and oxytocin receptor binding levels following ASI providing insights into the long-term effects of ASI in a time- and sex-specific manner.

The effect of Amantadine on recovery, postoperative cognitive dysfunction and pain after propofol anesthesia in mice

IntroductionPostoperative cognitive dysfunction (POCD) encompasses a spectrum of cognitive impairments following surgery, attributed to disruptions in brain homeostasis. The pathogenesis involves glutamate toxicity, GABA receptor dysfunction, and alterations in NMDA and AMPA receptors. This study aimed to investigate the impact of pre-anesthetic amantadine administration on postoperative recovery time, POCD, and stress-related pain levels when combined with propofol anesthesia. MethodsTwenty-four adult male BALB/C mice were divided into four groups: Control, Propofol, Amantadine, and Amantadine+Propofol. Amantadine and propofol doses were administered intraperitoneally based on previous literature. Recovery time, pain levels (assessed via tail pinch and hot plate tests), cognitive functions (evaluated through Morris Water Maze), and locomotor activity (measured via Open Field Test) were recorded. ResultsAmantadine administration significantly reduced recovery time from propofol anesthesia, prolonged pain perception, and preserved cognitive functions compared to propofol alone. The time spent in the target quadrant in the Morris Water Maze was significantly longer in groups receiving amantadine. Additionally, the distance covered until finding the platform was significantly shorter in the propofol-only group. DiscussionAmantadine's neuroprotective effects, attributed to its antagonistic action on glutamate and NMDA receptors, mitigate the detrimental effects of propofol on cognitive function and pain perception. This study highlights the potential of combining amantadine with propofol to enhance postoperative outcomes. ConclusionAmantadine administration before propofol anesthesia positively influenced postoperative recovery, cognitive function preservation, and stress-related pain perception in mice. These findings suggest a potential therapeutic strategy to mitigate POCD and pain associated with surgery.

The regenerative effect of exosomes isolated from mouse embryonic fibroblasts in mice created as a sciatic nerve crush injury model.

Exosomes (Exos) are candidates for functional recovery and regeneration following sciatic nerve crushed (SNC) injury due to their composition which can accelerate tissue regeneration. Therefore, mouse embryonic fibroblast-derived exosomes were evaluated for their regenerative capacity in SNC injury. In the study, 40Balb/c males (20 ± 5g) and two pregnant mice (for embryonic fibroblast tissue) were used and crushed injury was induced in the left sciatic nerve with an aneurysm clamp. Sciatic nerve model mice were randomly divided into 5 groups (n = 8; control, n = 8; sham, n = 8; SNC, n = 8; Mouse embryonic fibroblast exosome (mExo), n = 8; SNC + Mouse embryonic fibroblast exosome (SNC + mExo). Rotarod tests for motor functions and hot plate and von Frey tests for sensory functions were analyzed in the groups. Expression changes of exosome genes (RARRES1, NAGS, HOXA13, and MEIS1) immunohistochemical analysis of these gene proteins, and structural exosome NF-200 and S100 proteins were evaluated by confocal microscopy. Behavioral analyses showed that the damage in SNC was significant between groups on day14 and day28 (P < 0.05). In behavioral analyses, it was determined that motor functions and mechanical sensitivity lost in SNC were regained after mExo treatment. While expression of all genes was detected in MEF-derived exosomes, the high expression was MESI1 and the low expression was HOXA13. NF200, an indicator of axon number and neurofilament density, was found to decrease in SNC (P < 0.001) and increase after treatment, but not significantly. The decreased S100 protein levels in SNC and the increase detected after treatment were not significant. The expression of four mRNAs in mExos indicates that these genes may have an effect on regenerative processes after SNC injury. The regenerative process supported by tissue protein expressions demonstrates the therapeutic potential of mExo treatment.

Analgesic activity of a new cannabinoid CB1 receptor modulator

Aim. To study the analgesic activity, the effect on motor functions, and the potential ulcerogenic effect of a new 2H-chromene derivative, a cannabinoid CB1 receptor modulator (code name – CHR).Materials and methods. The analgesic activity of the CHR compound was studied when injected intragastrically at an effective dose of 5 mg / kg in mouse models of acute chemogenic pain (formalin test), acute visceral pain (the acetic acid-induced writhing test), and thermal nociception (hot plate test and tail-flick test). It was compared to the effect of tramadol and morphine or diclofenac sodium at doses of 20, 4 or 10 mg / kg, respectively. The effect of a single intragastric injection of the CHR compound at a dose of 5 mg / kg on motor activity was evaluated in the open field test. The potential ulcerogenic effect of the CHR compound at a dose of 5 mg / kg with repeated intragastric administration was compared with the effect of diclofenac sodium at a dose of 10 mg / kg.Results. With subplantar administration of formalin to mice, the 2H-chromene derivative reduced the number of pain reactions by 43–63% (p &lt; 0.05). With intraperitoneal administration of acetic acid to mice, it reduced the number of writhing responses by 50% and had the same analgesic effect as diclofenac sodium and tramadol. In the hot plate test, the CHR compound increased the latency time to painful stimuli by 34% (p &lt; 0.05). In the tailflick test, it increased the latency time to painful thermal sensations by 32% (p &lt; 0.05). The CHR compound at an effective dose of 5 mg / kg did not change the motor activity of mice in the open field test and did not cause the formation of erosions and ulcers in the gastric mucosa when administered repeatedly to rats.Conclusion. The 2H-chromene derivative CHR at an effective dose of 5 mg / kg has a pronounced analgesic effect in mouse models of chemogenic, visceral, and thermal pain, which is as strong as that of tramadol, morphine, and diclofenac sodium used at effective doses. The CHR compound at an effective dose does not inhibit motor functions and does not have an ulcerogenic effect.

Dihydrokoumine, a dual-target analgesic with reduced side effects isolated from a traditional Chinese medicine

IntroductionOpioids are the most common antinociceptive drugs, but long-term administration causes serious adverse side effects. Gelsemium elegans Benth. is traditionally used as an analgesic agent and mainly contains indole alkaloids with structures different from those in common opioids, indicating distinct pharmacological properties. This work aims to find a new analgesic from Gelsemium elegans Benth. and evaluate it in vitro and in vivo. MethodsDihydrokoumine was purified from Gelsemium elegans Benth. Binding to mu opioid receptor (MOR), M3 receptor (M3R) and other 15 G protein-coupled receptors were evaluated in vitro combined with molecular docking analysis. Analgesic efficacy and side effects were measured in vivo using hot-plate, formalin paw, and rotarod tests in mice. Cytotoxicity, acute toxicity in mice and pharmacokinetics were assessed. ResultsA MOR agonist, dihydrokoumine, was first identified from Gelsemium elegans Benth. Further investigations showed that dihydrokoumine exhibited selective partial agonist action on the MOR and antagonist action on the M3R among other 15 GPCRs. In in vivo mouse models, dihydrokoumine could relieve acute pain and chronic inflammatory pain without drug tolerance and sedative side effects. Additionally, we observed a good safety profile and favorable pharmacokinetic properties. ConclusionA MOR partial agonist/M3R antagonist analgesic with reduced side effects was isolated from a traditional Chinese medicine. This study bestows dihydrokoumine as a new dual-target analgesic and as a potential lead compound in pain management.

Melatonin mitigates vincristine-induced peripheral neuropathy by inhibiting TNF-α/astrocytes/microglial cells activation in the spinal cord of rats, while preserving vincristine's chemotherapeutic efficacy in lymphoma cells

Vincristine (VCR), an anti-tubulin chemotherapy agent, is known to cause peripheral and central nerve damage, inducing severe chemotherapy-induced peripheral neuropathy (CIPN). Although melatonin has been recently recognized for its potential anti-neuropathic effects, its efficacy in countering VCR-induced neuropathy remains unclear. This study examines the neuroprotective potential of melatonin against VCR-induced neuropathy using a rat model. Neuropathic pain was induced through 10 VCR injections (0.1 mg/kg/day i.p.), administered in two five-day cycles with a two-day break. Melatonin treatment started two days before VCR administration and continued daily throughout the experiment. Rats were assigned to five groups: control, VCR, and three melatonin-treated groups receiving VCR with melatonin (5, 10, or 20 mg/kg/day i.p.). We assessed mechanical (von-Frey and Randall-Selitto tests) and thermal (hot-plate and tail-flick tests) hyperalgesia, motor coordination (rotarod test), and sciatic nerve conduction velocity (NCV). Changes in body weight, spinal cord histopathology (H&E), and proinflammatory markers (TNF-α, IL-1β, and IL-6), reactive astrocytes (GFAP) and microglial cells (IBA-1) were also assessed, as well as spinal cord degeneration (Nissl stain) and demyelination (LFB stain and MBP). Finally, the effect of melatonin on the cytotoxic activity of VCR against EL4 lymphoma cells was assessed using an MTT assay. Our results indicated that melatonin coadministration with VCR preserved spinal cord architecture, elevated nociceptive thresholds, improved motor coordination, enhanced NCV, and maintained normal body weight gain. Melatonin also reduced inflammation, decreased reactive astrocytes and microglia, and prevented neurodegeneration and demyelination in the spinal cord. Importantly, melatonin did not affect VCR's cytotoxic activity in cancer cells.

Nigella sativa oil on chronic constrictive injury (CCI) induced neuropathic pain of sciatic nerve in Wistar rats

Background: Various adverse effects have been reported with conventional treatments of neuropathic pain. Nigella sativa (N. sativa), a medicinal herb, has been shown to possess several beneficiary effects. Objective: To assess the effects of N. sativa oil on neuropathic pain and ATP sensitive potassium channel (KATP) in Wistar rats. Methods: This experimental study was conducted on 120 Wistar rats (200±50gm). On the basis of treatments, all rats were grouped into Group I [normal control (NC) normal saline (NS) 5 ml/kg]; Group II [sham control (SC) {sham surgery + NS}], Group III [CCI control (CCIC) {Chronic constriction injury to sciatic nerve (CCI) + NS}]; Group IV [N. sativa oil experimental (NSOexp) {CCI + N.sativa (400 mg/kg)}], Group V [Glibenclamide experimental (Gliexp) {CCI + N. sativa (400 mg/kg) + glibenclamide (15 mg/kg)}] groups. Both the NSO and NS were administered orally once daily for consecutive 21 days and single dose of glibenclamide was given intraperitoneally on the day of experiment, to the respective rats. Then on the basis of neuropathic pain evaluation tests, all the groups were subdivided into ‘a’ [for sciatic functional index (SFI) in walking track analysis], ‘b’ [for tail flick latency (TFL) in cold tail immersion test], ‘c’ [for paw withdrawal threshold (PWT) in von Frey test], and ‘d’ (for rection time in hot plate test). The statistical analysis was done by one way ANOVA followed by Bonferroni post hoc test. Results: In this study, significantly (pd”0.001) higher SFI, TFL, PWT and reaction time were found in NSO exp rats when compared to those of CCIC rats. In addition, there were significant (pd”0.001) differences in the above-mentioned variables between rats of NSO exp group and Gliexp group. Conclusion: From the present study it might be concluded that, N. sativa prevents worsening of neuropathic pain in Wistar rats by blocking KATP channel. J Bangladesh Soc Physiol 2023;18(1): 35-45

Harmaline attenuates chemotherapy-induced peripheral neuropathy: Modulation of Nrf-2 pathway and NK-1 receptor signaling

Peripheral neuropathy, resulting from damage to peripheral nerves, manifests as weakness, numbness, and pain, primarily affecting extremities and significantly impairing quality of life, especially in the elderly. Current treatments often entail severe side effects, necessitating the exploration of alternative therapies. Harmaline, a β-carboline alkaloid derived from Peganum harmala, exhibits promising antioxidant and anti-inflammatory properties. This study aimed to assess the efficacy of harmaline in a vincristine-induced mouse model of peripheral neuropathy. Swiss albino mice received vincristine (0.1 mg/kg, i.p.) for 10 days to induce neuropathy. Harmaline (5 and 10 mg/kg, i.p.) was administered 30 min before vincristine and continued until day 14 to evaluate its protective effects. Behavioral assessments were conducted on days 7 and 14. Vincristine treatment significantly heightened sensitivity to cold, measured by cold plate and acetone drop tests, and to heat, assessed via the hot plate test, while also impairing motor coordination. Biochemical analyses revealed decreased levels of GSH and Nrf-2, alongside elevated TBARS and IL-1β levels in sciatic nerve tissue. Harmaline administration markedly alleviated both behavioral and biochemical alterations induced by vincristine, with the 10 mg/kg dose exhibiting the most pronounced effects. Notably, harmaline treatment elevated GSH and Nrf-2 levels while reducing TBARS and IL-1β. Furthermore, substance-P treatment reversed the protective effects of harmaline, implicating the NK-1 receptor in its mechanism of action. In conclusion, harmaline demonstrates significant potential in mitigating vincristine-induced peripheral neuropathy by reducing oxidative stress through Nrf-2 activation and lowering IL-1β levels, likely via NK-1 receptor inhibition.

Cannabigerol Reduces Acute and Chronic Hypernociception in Animals Exposed to Prenatal Hypoxia-Ischemia

Cannabigerol (CBG), a phytocannabinoid, has shown promise in pain management. Previous studies by our research group identified an increase in pain sensitivity as a consequence of prenatal hypoxia-ischemia (HI) in an animal model. This study aimed to investigate the efficacy of CBG in acute and chronic hyperalgesia induced by prenatal HI. A pharmacological screening was first conducted using hot plate and open-field tests to evaluate the antinociceptive and locomotor activities of animals administered with a 50 mg/kg oral dose of cannabis extract with a high CBG content. Prenatal HI was induced in pregnant rats, and the offspring were used to evaluate the acute antinociceptive effect of CBG in the formalin-induced peripheral pain model, while chronic antinociceptive effects were observed through spinal nerve ligation (SNL) surgery, a model used to induce neuropathic pain. Our results show that CBG exhibited an antinociceptive effect in the hot plate test without affecting the animals’ motor function in the open-field test. CBG significantly reduced formalin-induced reactivity in HI offspring during both the neurogenic and inflammatory phases. CBG treatment alleviated thermal and mechanical hypernociception induced by SNL. Biomolecular analysis revealed CBG’s ability to modulate expression, particularly reducing TNFα and Nav1.7 in HI male and female rats, respectively. These results highlight CBG as a potential antinociceptive agent in acute and chronic pain models, suggesting it as a promising therapeutic option without inducing motor impairment. Further research is needed to fully elucidate its mechanisms and clinical applications in pain management.

A mathematical multiple-dimensional strategy for Q-markers identification based on “five principles”: Tianshu Capsule for migraine treatment as an example

Ethnopharmacological relevanceQuality control is a critical element for Traditional Chinese medicine (TCM). Due to the varied chemical components, mechanisms of action, and pharmacological functions in TCM, ensuring quality is more challenging compared to chemical drugs. Then, the concept of quality markers (Q-markers) was proposed and ideal Q-markers for TCM prescriptions need to compliant with “five principles”, including pharmacological effectiveness, specificity, transfer and traceability, measurability, and prescription compatibility. Aim of the studyTo establish a mathematical multiple-dimensional “spider-web” strategy and identify the Q-markers of Tianshu capsule (TSC), a Chinese patent medicine for the treatment of migraine, following the “five principles” rules. Materials and methodsQ-marker candidates of TSC were firstly screened according to the HPLC fingerprints. Their contents in 10 batches of TSC and stabilities under high temperature, high humidity and in work solutions were determined quantitatively by HPLC-UV (measurability). Their existences in Gastrodiae Rhizoma, Chuanxiong Rhizoma, TSC, rat plasma and brain samples were investigated using HPLC-Q-TOF/MS (transfer and traceability). Their anti-migraine efficacies were evaluated by network pharmacology and mice hot-plate analgesia test; and their relationships with the property (flavor) of Gastrodiae Rhizoma or Chuanxiong Rhizoma were studied by molecular docking (effectiveness). Their contributions were defined based on their herb source according to the compatibility theories of Da Chuan Xiong Fang (compatibility). Their biosynthetic pathways were studied, and their frequencies detected in different plant families were calculated (specificity). Finally, an eight dimensional “spider-web” mode was developed for 10 components, and the regression area (RA) and the coefficient variation (CV) of each candidate were calculated after data normalization. ResultsTen components including gastrodin, parishin E, chlorogenic acid, ferulic acid, isochlorogenic acid A, senkyunolide I, H, A, Z-ligustilide and levistilide A were selected and evaluated as the Q-marker candidates. The results showed that gastrodin, senkyunolide I, and senkyunolide A had the higher RA and lower CV than other compounds with the established “spider-web” mode, indicating that they could be used as the Q-markers of TSC. ConclusionThe multi-dimensional “spider-web” mode based on “five principles” was firstly applied to identify the Q-markers of TSC, and it can be used as a practical strategy to discover Q-markers of other compounded prescriptions.

A Patent-Pending Ointment Containing Extracts of Five Different Plants Showed Antinociceptive and Anti-Inflammatory Mechanisms in Preclinical Studies.

Background/Objectives: The antinociceptive and anti-inflammatory effects of a patent-pending ointment containing plant extracts from Eucalyptus globulus, Curcuma longa, Hamamelis virginiana, Echinacea purpurea, and Zingiber officinale were evaluated. Methods: Plant extracts were chemically characterized by gas chromatography-mass spectroscopy. The antinociceptive activity of the ointment was assessed using the hot plate, tail flick, and formalin tests, whereas the anti-inflammatory activity was measured using the acute and chronic TPA-induced ear edema tests. Mechanisms of action were evaluated using inhibitors from signaling pathways related to pain response and by using histological analysis and assessing the expression and activity of pro-inflammatory mediators. Results: The ointment showed antinociceptive and anti-inflammatory effects like those observed with diclofenac gel (1.16% v/v) and ketoprofen gel (2.5% v/v). The antinociceptive actions of the ointment are mediated by the possible participation of the opiodergic system and the nitric oxide pathway. The anti-inflammatory response was characterized by a decrease in myeloperoxidase (MPO) activity and by a reduction in ear swelling and monocyte infiltration in the acute inflammation model. In the chronic model, the mechanism of action relied on a decrease in pro-inflammatory mediators such as COX-2, IL-1β, TNF-α, and MPO. An in-silico study with myristic acid, one of the compounds identified in the ointment's plant mixture, corroborated the in vivo results. Conclusions: The ointment showed antinociceptive activities mediated by the decrease in COX-2 and NO levels, and anti-inflammatory activity due to the reduction in IL-1β and TNFα levels, a reduction in MPO activity, and a decrease in NF-κB and COX-2 expression.

The Effect of a Caffeine and Nicotine Combination on Nicotine Withdrawal Syndrome in Mice.

Nicotine dependence is an important cause of excessive exposure to tobacco combustion compounds in most smokers. Nicotine replacement therapy is the main method to treat nicotine dependence, but it still has its shortcomings, such as the inability to mitigate withdrawal effects and limited applicability. It has been hypothesized that a combination of low-dose nicotine and caffeine could achieve the same psychological stimulation effect as a high dose of nicotine without causing nicotine withdrawal effects. To establish a model of nicotine dependence, male C57BL/6J mice were subcutaneously injected four times a day with nicotine (2 mg/kg) for 15 days and fed with water containing nicotine at the same time. They were randomly divided into four groups. After 24 h of withdrawal, different groups were injected with saline, nicotine (0.25 mg/kg or 0.1 mg/kg), or nicotine (0.1 mg/kg) and caffeine (20 mg/kg). Behavioral and physiological changes were evaluated by an assessment of physical signs, open field tests, elevated plus maze experiments, forced swimming tests, hot plate tests, and new-object-recognition tests. The changes in dopamine release in the prefrontal cortex (PFC) and ventral tegmental area (VTA) in the midbrain were analyzed using ELISA. The results showed that a combination of caffeine and nicotine could effectively relieve nicotine withdrawal syndrome, increase movement ability and pain thresholds, reduce anxiety and depression, enhance memory and cognitive ability, and increase the level of dopamine release in the PFC and VTA. Thus, caffeine combined with nicotine has potential as a stable and effective treatment option to help humans with smoking cessation.

A multi-target ligand (JM-20) prevents morphine-induced hyperalgesia in naïve and neuropathic rats

The present study examines the possible inhibitory effect of JM-20, a multi-target neuroprotective compound, on the development of morphine-induced hyperalgesia in Male Sprague-Dawley naïve rats. Additionally, the impact of JM-20 on chronic constriction injury (CCI) rats under chronic morphine exposure was investigated, and its efficacy in reducing mechanical hypersensitivity and histopathological changes in the sciatic nerve was assessed. JM-20 (20 mg/kg, per os [p.o.]), administered 60 min before morphine (10 mg/kg, s.c. twice daily at 12 h intervals) for ten days, significantly inhibited the development of morphine-induced hyperalgesia assessed using an electronic pressure-meter paw test, hot-plate, and formalin test, as well as the appearance of spontaneous withdrawal somatic symptoms in rats. Furthermore, JM-20 decreases spinal pro-inflammatory interleukin-1β and restores glutathione to close physiological concentrations, biomarkers directly related to the intensity of mechanical hypernociception. After CCI and sham surgery, co-treatment with JM-20 (10 mg/kg, p.o.) for five days decreased morphine increased-mechanical hypersensitivity, even 12 days after its discontinuation. Continued morphine treatment imposed a neuroinflammatory challenge in CCI animals, further increasing cellularity (>75% immune cell infiltration) with lymphocytes and macrophages. However, JM-20 co-treatment still reduced the presence of cellular infiltrates (51–75%) with a predominance of lymphocytes. Even in the absence of nerve injury, JM-20 attenuated the peripheral neuroinflammatory response observed in morphine-treated sham-operated animals (0% vs. 1–25%). These findings suggest that JM-20 could prevent morphine-induced hyperalgesia by anti-inflammatory and antioxidant mechanisms.

The Role of the Mu Opioid Receptors of the Medial Prefrontal Cortex in the Modulation of Analgesia Induced by Acute Restraint Stress in Male Mice.

Mu opioid receptors (MORs) represent a vital mechanism related to the modulation of stress-induced analgesia (SIA). Previous studies have reported on the gamma-aminobutyric acid (GABA)ergic "disinhibition" mechanisms of MORs on the descending pain modulatory pathway of SIA induced in the midbrain. However, the role of the MORs expressed in the medial prefrontal cortex (mPFC), one of the main cortical areas participating in pain modulation, in SIA remains completely unknown. In this study, we investigated the contributions of MORs expressed on glutamatergic (MORGlut) and GABAergic (MORGABA) neurons of the medial prefrontal cortex (mPFC), as well as the functional role and activity of neurons projecting from the mPFC to the periaqueductal gray (PAG) region, in male mice. We achieved this through a combination of hot-plate tests, c-fos staining, and 1 h acute restraint stress exposure tests. The results showed that our acute restraint stress protocol produced mPFC MOR-dependent SIA effects. In particular, MORGABA was found to play a major role in modulating the effects of SIA, whereas MORGlut seemed to be unconnected to the process. We also found that mPFC-PAG projections were efficiently activated and played key roles in the effects of SIA, and their activation was mediated by MORGABA to a large extent. These results indicated that the activation of mPFC MORGABA due to restraint stress was able to activate mPFC-PAG projections in a potential "disinhibition" pathway that produced analgesic effects. These findings provide a potential theoretical basis for pain treatment or drug screening targeting the mPFC.

Antinociceptive in vivo activity and chemical profiling by UHPLC-MS/MS of stem bark and leaves extracts of Ficus maxima Mill. (Moraceae)

Ethnopharmacological relevanceFicus maxima is a medicinal plant extensively used in traditional medicine by Indigenous peoples across Central and South America. It is a member of the family Moraceae, subgenus Pharmacosycea, employed in treating various conditions, including intestinal parasites, gingivitis, internal inflammations, and snake bites. Despite its significant pharmacological potential, the species remains underrepresented in scientific literature. Aim of the studyThis study aimed to evaluate the in vivo antinociceptive properties of leaf (ELFM) and stem bark (EBFM) extracts from Ficus maxima. Additionally, the chemical composition of these extracts was determined using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Materials and methodsPlant material was collected in Abaetetuba, Pará, Brazil, in October 2013 and subjected to static maceration to obtain crude ELFM and EBFM. Bio-guided fractionation was performed by sequential liquid-liquid partitioning with hexane (Hex), dichloromethane (DCM), and ethyl acetate (EtOAc), yielding the following fractions: ELFM-Hex and EBFM-Hex, ELFM-DCM and EBFM-DCM, and ELFM-EtOAc and EBFM-EtOAc. The biological activity of EBFM, ELFM, and their respective fractions were evaluated using the formalin-induced pain test and the hot plate test, followed by an assessment of their mechanisms of action. The UHPLC-MS/MS analysis was conducted using electrospray ionization (ESI) in both positive and negative modes. Metabolite annotation was facilitated by MS/MS libraries and molecular networks constructed on the GNPS platform. ResultsThe reactivity time to formalin in the neurogenic phase was reduced from 84.7 ± 7.6 s (100%) to 37.3 ± 4.7 s (44%), 33.1 ± 6.3 s (39%), 40.7 ± 7.4 s (48%), 57.2 ± 2.6 s (77%), 49.7 ± 4.1 s (58%), 46.8 ± 8.1 s (55%), and 52.4 ± 5.3 s (61%) after treatment with ASA, morphine, EBFM, ELFM, ELFM-Hex, ELFM-DCM, and ELFM-EtOAc at doses of 30 mg/kg, respectively. In the inflammatory phase, the reactivity time to formalin was reduced from 124.3 ± 25.9 s (100%) to 49.7 ± 4.7 s (40%), 9.8 ± 4.3 s (8%), 32.5 ± 8.5 s (26%), 59.8 ± 16.8 s (48%), and 54.4 ± 7.3 s (44%) after treatment with ASA, morphine, EBFM, ELFM, and ELFM-Hex at doses of 30 mg/kg, respectively. A reversal of the antinociceptive action of EBFM and ELFM was observed in the inflammatory phase after treatment with atropine, a muscarinic antagonist, and naloxone, an opioid antagonist, respectively. In the hot plate test, EBFM showed Antinociceptive Activity (AA) of 62.6 ± 9.2% after 90 min; however, there was a reversal of AA to 8.6 ± 2.8% when naloxone was used. The UHPLC-MS/MS metabolite analysis revealed the presence of loliolide (3), luteolin (13), lupeol (14), gallic acid (15), chlorogenic acid (16), pygenic acid A (17), and other metabolites from the alkaloids and fatty acids classes.

Simultaneous use of venlafaxine and calcium channel blockers on tolerance to morphine: The role of mitochondrial damage and oxidative stress in the brain

BackgroundOne of the reasons for tolerance to morphine is increased oxidative stress and dysfunction of cell mitochondria in the hippocampus. Venlafaxine and calcium channel blockers can protect mitochondrial function. The investigation of the role of mitochondrial damage and oxidative stress in the simultaneous use of venlafaxine and calcium channel blockers on the acute analgesic effects of morphine and the induction of tolerance to its effects in mice was assessed. MethodIn this experimental study, to induce tolerance to morphine, NMRI mice were treated with 50 mg/kg morphine for three consecutive days and 5 mg/kg morphine on the fourth day. Venlafaxine (20 mg/kg) alone or in combination with calcium channel blockers, nimodipine (10 mg/kg), and diltiazem (40 mg/kg) was administered 30 min before morphine, and the hot plate test was used. Then, hippocampal mitochondria were isolated by differential centrifugation method, and the levels of mitochondrial dehydrogenase activity, mitochondrial membrane potential, mitochondrial ROS production rate, as well as the content of glutathione and malondialdehyde in hippocampal mitochondria, were measured. ResultsThe administration of venlafaxine-nimodipine and venlafaxine-diltiazem increased morphine's acute analgesic effects (P < 0.05) and reduced the induction and expression of tolerance to the analgesic effects of morphine (P < 0.05). Morphine significantly decreased MTT and GSH and increased MDA, mitochondrial membrane damage, and ROS compared to the control group (P < 0.01). Injection of venlafaxine-nimodipine and also venlafaxine-diltiazem 30 min before morphine can improve these alterations (P < 0.05). Discussion and conclusionOur data showed that the simultaneous use of venlafaxine with calcium channel blockers could increase the acute analgesic effects of morphine and reduce the induction and expression of tolerance to it. Also, the preventive and protective roles of simultaneous administration of venlafaxine and calcium channel blockers on morphine-induced mitochondrial oxidative stress and damage during the tolerance test were achieved.