Opioidergic Receptors Research Articles

Activation of epidermal growth factor receptors in triple-negative breast cancer cells by morphine; analysis through Raman spectroscopy and machine learning

Triple negative breast cancer (TNBC) is a very aggressive form of breast cancer, and the analgesic drug morphine has been shown to promote the proliferation of TNBC cells. This article investigates whether morphine causes activation of epidermal growth factor receptors (EGFR), the roles of μ-opioid and EGFR receptors on TNBC cell proliferation and migration. While examining the changes with molecular techniques, we also aimed to investigate the analysis ability of Raman spectroscopy and machine learning-based approach. Effects of morphine on the proliferation and migration of MDA.MB.231 cells were evaluated by MTT and scratch wound-healing tests, respectively. Morphine-induced phosphorylation of the EGFR was analyzed by western blotting in the presence and absence of μ-receptor antagonist naltrexone and the EGFR-tyrosine kinase inhibitor gefitinib. Morphine-induced EGFR phosphorylation and cell migration were significantly inhibited by pretreatments with both naltrexone and gefitinib; however, morphine-increased cell proliferation was inhibited only by naltrexone. While morphine-induced changes were observed in the Raman scatterings of the cells, the inhibitory effect of naltrexone was analyzed with similarity to the control group. Principal component analysis (PCA) of the Raman confirmed the epidermal growth factor (EGF)-like effect of morphine and was inhibited by naltrexone and partly by gefitinib pretreatments. Our in vitro results suggest that combining morphine with an EGFR inhibitor or a peripherally acting opioidergic receptor antagonist may be a good strategy for pain relief without triggering cancer proliferation and migration in TNBC patients. In addition, our results demonstrated the feasibility of the Raman spectroscopy and machine learning-based approach as an effective method to investigate the effects of agents in cancer cells without the need for complex and time-consuming sample preparation. The support vector machine (SVM) with linear kernel automatically classified the effects of drugs on cancer cells with ∼95% accuracy.

Antinociceptive and Anti-Inflammatory Like Effects of Berberis baluchistanica.

Numerous therapeutic agents are in clinical practice for the treatment of inflammatory and painful conditions, but their applications have been challenged by various side /toxic effects. Therefore, new effective and safe therapies are most warrant, for which medicinal plant could be a significant alternative. Berberis baluchistanica has traditionally been used as analgesic and anti-inflammatory without any scientific background. The current study was designed to evaluate the analgesic and anti-inflammatory like effects of extract B. baluchistanica in animal models. For the study of antinociceptive effect, an extractof B. baluchistanica (100, 200 and 300 mg/kg i.p.), was tested in acetic acid-induced writhing and formalin tests. While for the anti-inflammatory action, carrageenan-induced paw edema, cotton pellet induced granuloma and xylene induced ear edema tests were used. The results showed the significant dose-dependent antinociceptive effect of extract of B. baluchistanica in acetic acid-induced writhing and formalin-induced flinching behavior tests. However, the effect was strongly antagonized by the injection of naloxone, suggesting the expression via opioidergic receptors. Similarly, strong anti-inflammatory action was illustrated in carrageenan- induced paw edema, cotton pellet induced granuloma and xylene induced ear edema tests and thus provided evidence for the versatile phytochemical nature of its phytochemical. In short, it is concluded that the extract of B. baluchistanica exhibited significant antinociceptive and anti-inflammatory effects in animal models. Further detailed studies on the efficacy and safety as well as on the phytochemical investigation are required to ascertain its clinical uses.

Beta 2 Adrenergic Receptor Antagonist Propranolol and Opioidergic Receptor Antagonist Naltrexone Produce Synergistic Effects on Breast Cancer Growth Prevention by Acting on Cancer Cells and Immune Environment in a Preclinical Model of Breast Cancer.

Simple SummaryHere, we show that propranolol, a beta blocker used to treat high blood pressure, and naltrexone, an opiate antagonist used for drug and alcohol dependence, when combined, produce marked inhibitory effects on tumor growth and tumor mass while improving the survival rate, increasing NK cell activity, and reducing inflammatory cytokine levels in plasma. These antitumor effects resulted from a reduction in tumor cell proliferation, the induction of cellular apoptosis, and the prevention of epithelial–mesenchymal transition in the tumor. Our data identify a novel treatment with a combination of approved classes of drugs in preclinical breast cancer models.Cancer progression is known to be promoted by increased body stress caused by elevated beta-adrenergic and opioidergic nervous system activities. The effects of β2-adrenergic blocker propranolol (PRO) and μ-opioid receptor antagonist naltrexone (NTX) were tested using a preclinical model of human breast cancer. These drugs, individually, and more potently when combined, inhibited the cell growth and progression of breast cancer cells in vitro in cultures, and in vivo in rat xenografts. The antitumor activities of these drugs were associated with direct cell intrinsic effects, including increased cell growth arrest, elevated levels of apoptotic proteins, and reduced production of epithelial–mesenchymal transition factors by the tumor cells, as well as effects on innate immune activation and reduced inflammatory cytokine levels in plasma. These data suggest that the combined treatments of PRO and NTX produce impressive antitumor effects in the preclinical breast cancer model, and thereby may provide a new combinatorial treatment strategy with more clinical treatment modalities.

5-HT1A Serotonergic, α-Adrenergic and Opioidergic Receptors Mediate the Analgesic Efficacy of Vortioxetine in Mice.

Vortioxetine is a multimodal antidepressant drug that affects several brain neurochemicals and has the potential to induce various pharmacological effects on the central nervous system. Therefore, we investigated the centrally mediated analgesic efficacy of this drug and the mechanisms underlying this effect. Analgesic activity of vortioxetine (5, 10 and 20 mg/kg, p.o.) was examined by tail-clip, tail-immersion and hot-plate tests. Motor performance of animals was evaluated using Rota-rod device. Time course measurements (30–180 min) showed that vortioxetine (10 and 20 mg/kg) administrations significantly increased the response latency, percent maximum possible effect and area under the curve values in all of the nociceptive tests. These data pointed out the analgesic effect of vortioxetine on central pathways carrying acute thermal and mechanical nociceptive stimuli. Vortioxetine did not alter the motor coordination of mice indicating that the analgesic activity of this drug was specific. In mechanistic studies, pre-treatments with p-chlorophenylalanine (serotonin-synthesis inhibitor), NAN-190 (serotonin 5-HT1A receptor antagonist), α-methyl-para-tyrosine (catecholamine-synthesis inhibitor), phentolamine (non-selective α-adrenoceptor blocker), and naloxone (non-selective opioid receptor blocker) antagonised the vortioxetine-induced analgesia. Obtained findings indicated that vortioxetine-induced analgesia is mediated by 5-HT1A serotonergic, α-adrenergic and opioidergic receptors, and contributions of central serotonergic and catecholaminergic neurotransmissions are critical for this effect.

Resveratrol: A Pleiotropic Phytoconstituent

Resveratrol (RSV) is a plant polyphenol or phytolexin phytoconstituents obtained from the grapes, berries, peanut, and wine. RSV is obtained from natural source and regarded as safe, effective, and hepatoprotective drug with no other serious organ toxicities are reported yet. This property of RSV makes it advantageous over the allopathic medicine having symptomatic cure and plethora of adverse effects. It’s a cheap and widely available phytoconstituent approved in the global market in the active form as trans-resveratrol. It has multiple pharmacological actions including, analgesic, anti-inflammatory, anti-anxiety, anti-parkinsonian, anti-alzheimers, antioxidant, antidepressant, anti-cancer, anti-diabetic, anti-atherosclerotic effects. These effects are mediated via modulation of diverse underlying endogenous molecules like reactive oxygen species, nitric oxide, malonaldehyde, neutrophil, sirtulin, cyclo-oxygenase, inducible nitric oxide syntheses, superoxide dismutase, catalase, glutathione s-transferase, alpha-secretase, metalloproteinases, C-reactive protein, dopamine, nor-adrenaline, serotonin, cytokines (interleukins), nuclear factor kappa, signal transducer activator of transcription, brain derived neural nactor, neuropeptide, hypothalamo-pitutary axis, astroglia, mitochondrial dysfunction, glutamate, adrenergic, cholinergic, opioidergic, and purinergic receptors. Researchers are trying to explore its additional health benefits and preparing new analogues for better survival in the field. Present review will help to enlighten the multi-target pleiotropic pharmacological nature of a RSV in relation to the variety of the molecular targets modulation through extensive web science literature survey.

Anti-inflammatory and antinociceptive activities of a phenylpropanoid-enriched fraction of Duguetia furfuracea.

A previous study reported the in vivo anti-inflammatory and antinociceptive activities of essential oil of the underground stem bark of Duguetia furfuracea, termed EODf. This study aimed to obtain a phenylpropanoid-enriched fraction from the D. furfuracea (EFDf) essential oil and to investigate its anti-inflammatory and antinociceptive effects. The chemical composition of the EFDf was determined by gas chromatography-mass spectrometry (GC-MS). The in vivo anti-inflammatory activity was evaluated with a lipopolysaccharide (LPS)-induced paw oedema model. The effects of the EFDf on the polymorphonuclear leukocyte recruitment and the inducible nitric oxide synthase (iNOS) expression were evaluated in mice footpads. Moreover, the in vivo antinociceptive effect was assayed using the formalin test and the LPS-induced thermal hyperalgesia model. In the EFDf, 8 major compounds were identified, with α-asarone (36.4%) and 2,4,5-trimethoxystyrene (27.8%) the main constituents. A higher concentration of phenylpropanoid derivatives was found in the EFDf, 64.2% compared to the EODf (38%). The oral (p.o.) treatment with the EFDf at a dose of 3mg/kg significantly attenuated the paw oedema, polymorphonuclear leukocyte migration, iNOS expression, and tumour necrosis factor alpha (TNF-α) production. The EFDf (10 and 30mg/kg) also inhibited both phases of the formalin test and caused a significant increase in the reaction time in the LPS-induced thermal hyperalgesia model. Finally, EFDf-treated animals did not show any alteration of motor coordination. The results suggest that the enrichment of 2,4,5-trimethoxystyrene and α-asarone enhances the anti-inflammatory activity of the EFDf compared to the EODf. In contrast, the antinociception promoted by the EFDf was similar to the EODf and was mediated via activation of adenosinergic and opioidergic receptors.

Non-Opioid Treatments for Opioid Use Disorder: Rationales and Data to Date.

Opioid use disorder (OUD) represents a major public health problem that affects millions of people in the USA and worldwide. The relapsing and recurring aspect of OUD, driven by lasting neurobiological adaptations at different reward centres in the brain, represents a major obstacle towards successful long-term remission from opioid use. Currently, three drugs that modulate the function of the opioidergic receptors, methadone, buprenorphine and naltrexone have been approved by the US Food and Drug Administration (FDA) to treat OUD. In this review, we discuss the limitations and challenges associated with the current maintenance and medication-assisted withdrawal strategies commonly used to treat OUD. We further explore the involvement of glutamatergic, endocannabinoid and orexin signaling systems in the development, maintenance and expression of addiction-like behaviours in animal models of opioid addiction, and as potential and novel targets to expand therapeutic options to treat OUD. Despite a growing preclinical literature highlighting the role of these potential targets in animal models of opioid addiction, clinical and translational studies for novel treatments of OUD remain limited and inconclusive. Further preclinical and clinical investigations are needed to expand the arsenal of primary treatment options and adjuncts to maximise efficacy and prevent relapse.

Interaction Between Oxytocin and Opioidergic System on Food Intake Regulation in Neonatal Layer Type Chicken

The aim of the current study was to determine possible interaction of central oxytocin and opioidergic system on food intake regulation in neonatal layer-type chicken. In experiment 1, FD3 chicken ICV injected with control solution, oxytocin (10 µg), β-FNA (µ receptor antagonist, 5 µg) and oxytocin (10 µg) + β-FNA were injected. Experiments 2–6 were similar to experiments 1, except chicken injected with nor-BNI (κ receptor antagonist, 5 µg), NTI (δ receptor antagonist, 5 µg), DAMGO (µ receptor agonist, 62.25 pmol), U-50488H (κ receptor agonist, 10 nmol), DPDPE (δ receptor agonist, 20 pmol) instead of β-FNA. In experiment 7, control solution, DAMGO (125 pmol), d(CH2)5Tyr(Me)-[Orn8]-vasotocin (oxytocin antagonist, 5 µg) and DAMGO + d(CH2)5Tyr(Me)-[Orn8]-vasotocin were ICV injected to FD3 chicken. Experiments 8 and 9 were similar to experiments 7, except chicken injected with U-50488H (30 nmol) and DPDPE (40 pmol) instead of DAMGO. Then, cumulative food intake was recorded at 30, 60 and 120 min after injection. According to the results, ICV injection of the oxytocin (10 µg) significantly decreased food intake compared to control group (P < 0.05). Co-injection of the oxytocin + β-FNA and oxytocin + U-50488H significantly decreased hypophagic effect of the oxytocin (P < 0.05). While, co-injection of the oxytocin + nor-BNI or oxytocin + DAMGO significantly amplified hypophagic effect of the oxytocin in chicken (P < 0.05). In addition, ICV injection of DAMGO (125 pmol) significantly decreased cumulative food intake compared to control group (P < 0.05). However, co-addministration of the DAMGO + (CH2)5Tyr(Me)-[Orn8]-vasotocin significantly decreased hypophagic effect of the DAMGO (P < 0.05) in chicken. These results suggested there are interconnection between oxytocin and opioidergic system on central food intake regulation, which mediates via µ and κ opioidergic receptors in neonatal layer-type chicken.

Abstract 3006: A novel strategy of targeting opioidergic receptors to potentially reduce human breast cancer cell proliferation, colony formation, invasion, and migration

Abstract Breast cancer is the second most prevalent cancer after lung cancer among American women. The efficacy of current antitumor therapies is still quite limited. Endogenous opioid peptides, such as endorphin, which is involved in body stress controlling mechanisms, have been shown to enhance immune function and prevent cancer growth and progression in various animal models of cancers. Therefore, targeting the endogenous opioid peptides receptors in the regulation of cancer chemoprevention may offer new promise for the design of therapeutic strategies. Our previous studies have shown differential actions of mu-opioid receptor (MOR) and delta opioid receptor (DOR) on various cell types. In this study we tested the effects of a MOR antagonist naltrexone (NTX) and a DOR agonist (D-Ala2-,N-Me-Phe4,Gly-ol Enkephalin; DPDPE) on proliferation and invasion of human breast cancer cells of different molecular subtype such as T47D (Luminal A), MDA-MB-231 (triple negative, Claudin-Low) and MDA-MB- 468 (triple negative, basal A) in cultures. We used cytotoxicity, clonogenic, cell migration and cell invasion assays to identify effects of these drugs on cancer cells. We found that both NTX and DPDPE have significant cytotoxic effects on these breast cancer cells. Our work from clonogenic, cell migration and cell invasion assays showed that both NTX and DPDPE inhibit the formation of colony, migration and invasion of cancer cells in a concentration-dependent manner. These data suggest that naltrexone and DPDPE have anticancer efficacy in subtypes of human breast cancer cells. The anticancer effects varied depending on the concentration of the drugs and the subtype of breast cancer cells. (Supported by NIH grant R01 CA20863201). Citation Format: Sengottuvelan Murugan, Vanisha Patel, Dipak K. Sarkar. A novel strategy of targeting opioidergic receptors to potentially reduce human breast cancer cell proliferation, colony formation, invasion, and migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3006.

Antinociceptive profiles and mechanisms of centrally administered oxyntomodulin in various mouse pain models

In the present study, the antinociceptive profiles of oxyntomodulin were examined in ICR mice. Oxyntomodulin administered intrathecally (i.t.) and intracerebroventricularly (i.c.v.) (from 1 to 5μg/5μl) showed an antinociceptive effect in a dose-dependent manner as measured in the acetic acid-induced writhing test. Moreover, cumulative response time of nociceptive behaviors induced by intraplantar formalin injection was reduced by i.t. or i.c.v. treatment with oxyntomodulin during the second, but not the first phase. In addition, the cumulative nociceptive response time after i.t. injection with substance P (0.7μg), glutamate (20μg), and pro-inflammatory cytokines such as TNF-α, IL-β or IFN-γ (100pg/5μl) was diminished by spinally or supraspinally administered oxyntomodulin. However, i.t. and i.c.v. treatment with oxyntomodulin did not affect latencies of the tail-flick and hot-plate paw-licking responses. Furthermore, the i.t. pretreatment with yohimbine (adrenergic receptor antagonist), but not naloxone (an opioid receptor antagonist) or methysergide (a serotonergic receptor antagonist), attenuated antinociceptive effect induced by oxyntomodulin administered i.c.v. in the writhing test. The i.c.v. or i.t. pretreatment with oxyntomodulin attenuated formalin-induced increase of phosphorlated ERK (p-ERK) expression in the spinal cord. Our results suggest that centrally administered oxyntomodulin shows an antinociceptive property in various pain models except for thermal-induced nociception. Furthermore, supraspinally administered oxyntomodulin-induced antinociception may be mediated by spinal adrenergic receptors, but not serotonergic and opioidergic receptors. Furthermore, the antinociception induced by oxyntomodulin appears to be mediated by reduced formalin-induced p-ERK expression in the spinal cord.

Antiallodynic activity of leflunomide is partially inhibited by naltrexone and glibenclamide and associated with reduced production of TNF-α and CXCL-1

Leflunomide, an immunosuppressive drug approved for the treatment of patients with rheumatoid arthritis, exhibits many mechanisms which may affect the nociceptive processing. Therefore, the present study aimed to evaluate the effect induced by leflunomide on the mechanical allodynia in models of inflammatory and neuropathic pain in mice and investigate mechanisms mediating such effects. Per os (p.o.) administration of leflunomide (25, 50 or 100mg/kg) inhibited the inflammatory edema and mechanical allodynia induced by intraplantar carrageenan. Even ongoing inflammatory edema and mechanical allodynia were reduced by leflunomide. Previous administration of naltrexone (10mg/kg, intraperitoneal) or glibenclamide (40mg/kg, p.o.) partially attenuated leflunomide antiallodynic activity. A single administration of leflunomide (50 or 100mg/kg, p.o.) also partially inhibited ongoing mechanical allodynia induced by chronic constriction injury (CCI) or repeated administrations of paclitaxel. The antiallodynic effect induced by leflunomide (50 or 100mg/kg, p.o.) in the model of neuropathic pain induced by CCI was associated with reduced production of tumor necrosis factor-α both at the injury site and ipsilateral paw. Leflunomide also reduced production of the chemokine CXCL-1 at the paw ipsilateral to the injury site. Concluding, leflunomide partially inhibited ongoing mechanical allodynia in models of inflammatory and neuropathic pain. The antiallodynic effect was associated with activation of opioidergic receptors and ATP-sensitive potassium channels and reduced production of inflammatory mediators. These data indicate leflunomide as a drug that should be further investigated aiming to identify a new analgesic pharmacotherapy and reinforces repositioning as an important strategy to identify new uses for approved drugs.

Temporal and spatial dynamics of peripheral afferent-evoked activity in the dorsal horn recorded in rat spinal cord slices.

In the present study, multi-electrode array recording was used to examine dorsal horn activity following stimulation of primary afferents in a rat dorsal root attached-spinal cord slice preparation. The multi-electrode array probe was placed under the dorsal horn slice and local field potentials evoked by stimulation on the dorsal root were analyzed. Three kinds of dorsal root-evoked responses were identified. In lamina IIo, local field potentials exhibited P1 (peak latency 1.46±0.08ms), N1 (2.77±0.18ms, n=12), N2 (7.31±0.48ms), N3 (12.12±0.73ms) and P2(18.30±0.80ms) waves. In lamina IIi local field potentials exhibited P (1.99±0.10ms), N1 (3.35±0.17ms) and N2 (8.58±0.44ms) waves. In laminae III-VI, local field potentials exhibited P1 (3.01±0.07ms), P2 (7.02±0.21ms) and N waves (22.57±0.79ms). Sweep spread was calculated by two dimensional current source density (2D-CSD) analysis. Both α-amino-3-hydroxy-5-methylisoxazole-4-propionic a/kainate and N-methyl-d-aspartate-type glutamate receptors participated in this neuronal circuitry. Morphine diminished local field potentials. Gabapentin diminished the negative components in lamina II and P2 component in lamina IIo, but increased the positive components in lamina IIi and laminae III-VI. The present study revealed that functional dorsal horn activity was preserved in the spinal cord slice preparation. Glutamatergic synapses were crucially involved in information processing. Opioid interneurons and gabapentin may play a modulatory role in regulating signal flows in the dorsal horn. Taken together, these results identify a spatio-temporal profile of dorsal horn activity evoked by dorsal root stimulation, and implicate glutamatergic and opioidergic receptors and gabapentin in this activity.

The efficacy of combination treatment of gabapentin and electro-acupuncture on paclitaxel-induced neuropathic pain.

Paclitaxel, a chemotherapeutic drug, induces severe peripheral neuropathy. Gabapentin (GBT) is a first line agent used to treat neuropathic pain, and its effect is mediated by spinal noradrenergic and muscarinic cholinergic receptors. Electro-acupuncture (EA) is used for treating various types of pain via its action through spinal opioidergic and noradrenergic receptors. Here, we investigated whether combined treatment of these two agents could exert a synergistic effect on paclitaxel-induced cold and mechanical allodynia, which were assessed by the acetone drop test and von Frey filament assay, respectively. Significant signs of allodynia were observed after four paclitaxel injections (a cumulative dose of 8 mg/kg, i.p.). GBT (3, 30, and 100 mg/kg, i.p.) or EA (ST36, Zusanli) alone produced dose-dependent anti-allodynic effects. The medium and highest doses of GBT (30 and 100 mg/kg) provided a strong analgesic effect, but they induced motor dysfunction in Rota-rod tests. On the contrary, the lowest dose of GBT (3 mg/kg) did not induce motor weakness, but it provided a brief analgesic effect. The combination of the lowest dose of GBT and EA resulted in a greater and longer effect, without inducing motor dysfunction. This effect on mechanical allodynia was blocked by spinal opioidergic (naloxone, 20 μg), or noradrenergic (idazoxan, 10 μg) receptor antagonist, whereas on cold allodynia, only opioidergic receptor antagonist blocked the effect. In conclusion, the combination of the lowest dose of GBT and EA has a robust and enduring analgesic action against paclitaxel-induced neuropathic pain, and it should be considered as an alternative treatment method.

Mechanisms Underlying Anti-hyperalgesic Properties of Kaempferol-3,7- di-O-α-L-rhamnopyranoside Isolated from Dryopteris cycadina

The present study was designed to evaluate the anti-hyperalgesic effect of kaempferol-3,7-di-O-α-L-rhamnopyranoside isolated from the ethyl acetate soluble part of Dryopteris cycadina. Pretreatment of the compound at the doses of 2.5, 5, and 10 mg/kg caused a significant reduction in abdominal constrictions in acetic acid-induced writhing test with maximum effect of 63.03% (P < 0.001) at 10 mg/kg i.p. When subjected in formalin test, it evoked a marked antinociceptive effect in both phases in a dose-dependent manner. The maximum (p < 0.01) pain-inhibiting effects were 61.36% and 65.89% in 1st and 2nd phases at 10 mg/kg i.p., respectively. Administration of atropine (non-selective cholinergic receptor antagonist) significantly (p < 0.05) antagonized the antihyperalgesic effect of the compound, while glibenclamide and naloxone did not alter the induced antinociceptive effect and thus, antinociceptive activity of the compound is mediated, at least in part, through cholinergic system antagonism; independent of calcium channel and opioidergic receptor participation. Furthermore, docking studies underlined strong COX-2 inhibitory activity of the compound. Our data concluded that overall analgesic activity of the compound seems to involve COX-2 inhibition and activation of cholinergic receptors. However, further detailed studies are required in this direction to confirm the analgesic effect of the compound for its possible clinical utility.

Anti-nociceptive Activity of Ethnomedicinally Important Analgesic Plant Isodon rugosus Wall. ex Benth: Mechanistic Study and Identifications of Bioactive Compounds.

Isodon rugosus Wall. ex Benth. is extensively used as traditional medicine for the management of various types of pain including tooth ache, gastric pain, abdominal pain, ear ache, and generalized body pain. The current study is designed to scientifically verify the purported uses of I. rugosus as analgesic agent and to figure out its possible mechanism of action. Bioactive compounds responsible for analgesic activity were identified using GC and GC-MS analysis. Analgesic potentials were evaluated using acetic acid induced writhing, hot plate test, and formalin induced paw licking test. In acetic acid induced writhing chloroform fraction (Ir.Chf) exhibited 53% analgesia while formalin test displayed 61% inhibition at phase-I and 45% at phase-II respectively at a dose of 100 mg/kg. Similarly, in hot plate test Ir.Chf displayed average reaction time of 7 min at 15, 30, 45, and 60 min intervals. The possible mechanism of action was found to be the central pathway via opioidergic receptors as the mice showed morphine like analgesic activity at pre-administration of naloxone (opioid antagonist) in hot plate and formalin tests. In GC-MS analysis, 83 compounds were identified among which eight compounds including benzyl alcohol, sebacic acid, myristic acid, phytol, sugiol, Tocopherol, α-Amyrin, and stigmasterol were sorted out as previously reported analgesic compounds. Current study revealed that analgesic potential of I. rugosus can attributed to the presence of analgesic compounds. It may also be concluded that opioids receptors are involved in the analgesic mechanism of I. rugosus due to effective antagonism of nalaxone.

Gentle Mechanical Skin Stimulation Inhibits Micturition Contractions via the Spinal Opioidergic System and by Decreasing Both Ascending and Descending Transmissions of the Micturition Reflex in the Spinal Cord.

Recently, we found that gentle mechanical skin stimulation inhibits the micturition reflex in anesthetized rats. However, the central mechanisms underlying this inhibition have not been determined. This study aimed to clarify the central neural mechanisms underlying this inhibitory effect. In urethane-anesthetized rats, cutaneous stimuli were applied for 1 min to the skin of the perineum using an elastic polymer roller with a smooth, soft surface. Inhibition of rhythmic micturition contractions by perineal stimulation was abolished by naloxone, an antagonist of opioidergic receptors, administered into the intrathecal space of the lumbosacral spinal cord at doses of 2–20 μg but was not affected by the same doses of naloxone administered into the subarachnoid space of the cisterna magna. Next, we examined whether perineal rolling stimulation inhibited the descending and ascending limbs of the micturition reflex. Perineal rolling stimulation inhibited bladder contractions induced by electrical stimulation of the pontine micturition center (PMC) or the descending tract of the micturition reflex pathway. It also inhibited the bladder distension-induced increase in the blood flow of the dorsal cord at L5–S1, reflecting the neural activity of this area, as well as pelvic afferent-evoked field potentials in the dorsal commissure at the lumbosacral level; these areas contain long ascending neurons to the PMC. Neuronal activities in this center were also inhibited by the rolling stimulation. These results suggest that the perineal rolling stimulation activates the spinal opioidergic system and inhibits both ascending and descending transmissions of the micturition reflex pathway in the spinal cord. These inhibitions would lead to the shutting down of positive feedback between the bladder and the PMC, resulting in inhibition of the micturition reflex. Based on the central neural mechanisms we show here, gentle perineal stimulation may be applicable to several different types of overactive bladder.

Anti-nociceptive and antioxidant activities of an aqueous leaf extract of &lt;i&gt;Corchorus olitorius &lt;/i&gt;L. (Tiliaceae)

A preliminary study had shown that C. olitorius has analgesic activity possibly mediated through opioidergic pathway. The study was a follow up work to evaluate the anti-nociceptive effects and other possible mechanisms of action of an aqueous leaf extract of C. olitorius (COE) using formalin-induced nociception test. COE was screened for its analgesic, and antioxidant activities. The anti-nociceptive effect of COE (3x10-2, 1x10-1 and 3x10-1 g kg-1, p.o), and morphine (1x10-3, 3x10-3 and 1x10-2 gkg-1, i.p.) were evaluated using the formalin-induced nociception test. The study showed that C. olitorius has analgesic activity possibly mediated through opioidergic pathway. COE produced significant (P ˂ 0.05) dose-dependent antinociceptive effects similar to morphine in both phases of formalin-induced nociception. The extract showed free radical scavenging properties and different phyto-constituents such as alkaloids, flavonoids, saponins, cardiac glycosides, tannins, anthraquinones and terpenoids were identified. COE has both central and peripheral anti-nociceptive effects mediated through opioidergic receptor activation and also partly through ATP-sensitive K+ channel activation systems. The findings confirms earlier reports, and further shows that C. olitorius produces anti-nociception by interrupting many pain processing pathways. Results further suggest that the extract (COE) might possess some chemical constituents that are responsible for the analgesic and the antioxidant activities.Keywords: Naloxone, glibenclamide, morphine, nociception, DPPH, formalin test.

Antinociceptive mechanisms of Bunium persicum essential oil in the mouse writhing test: role of opioidergic and histaminergic systems

Bunium persicum (Boiss.) is an economically important medicinal plant growing wildly in arid regions in Iran. The fruit of B. persicum is widely used in traditional Iranian medicine to control colic pain and dysmen - orrhoea. The aim of the current study was to determine antinociceptive mechanisms of B. persicum essential oil using an acetic acid-induced writhing test as a model of visceral pain and to determine the possible involvement of opioidergic, serotoninergic and histaminergic systems on antinociceptive mechanisms of B. persicum in male mice. In experiment 1, B. persicum was intraperitoneally ( i.p.) injected (0.001, 0.01, 0.05, 0.1, 0.5 and 1%; 10 ml/kg) in Tween-80 (0.5%) and a writhing test served as a model of visceral pain. In experiments 2-5, opioidergic receptor antagonist (naloxone, 2 mg/kg), serotonergic receptor antagonist (cyproheptadine, 4 mg/kg), histamine H 1 -recep- tor antagonist (chlorpheniramine, 20 mg/kg) and histamine H 2 -receptor antagonist (cimetidine, 12.5mg/kg) injection was followed by B. persicum (0.01%; 10 ml/kg) and the writhing test response was measured for 30 min. According to the results, essential oil of B. persicum, administered i.p. (0.001, 0.01, 0.05, 0.1, 0.5, and 1%; 10 ml/kg) in Tween-80 (0.5%), elicited antinociceptive effects in a dose-dependent manner. Moreover, the antinociceptive effect of B. persicum was significantly attenuated by pre-treatment with naloxone, chlorpheniramine and cimeti - dine (P < 0.001). These results suggest that B. persicum-induced analgesia may be mediated via opioidergic and histamine H 1 and H 2 receptors.

Gabaergic and opioid receptors mediate the facilitation of NaCl intake induced by α2-adrenergic activation in the lateral parabrachial nucleus

Alpha2-adrenergic, gabaergic or opioidergic activation in the lateral parabrachial nucleus (LPBN) increases sodium intake. In the present study, we investigated the effects of single or combined blockade of opioidergic and gabaergic receptors in the LPBN on the increase of 0.3M NaCl intake induced by α2-adrenoceptor activation in the LPBN. Male Holtzman rats (n=5–9/group) with cannulas implanted bilaterally in the LPBN were treated with the diuretic furosemide (10mg/kgbwt.) combined with low dose of the angiotensin converting enzyme inhibitor captopril (5mg/kgbwt.) subcutaneously. Bilateral injections of moxonidine (alpha2-adrenergic/imidazoline receptor agonist, 0.5nmol) into the LPBN increased furosemide+captopril-induced 0.3M NaCl intake (25.8±1.4, vs. vehicle: 3.8±1.1ml/60min). The opioidergic receptor antagonist naloxone (100nmol) or the GABAA receptor antagonist bicuculline (5nmol) injected into the LPBN partially reduced the increase of 0.3M NaCl intake produced by LPBN moxonidine (11.8±4.0 and 22.8±4.5, respectively, vs. vehicle+moxonidine: 31.6±4.0ml/60min, respectively). Similar to the treatment with each antagonist alone, the combined injections of naloxone (100nmol) and bicuculline (5nmol) into the LPBN also partially reduced moxonidine effects on 0.3M NaCl intake (15.5±6.5ml/60min). The GABAB receptor antagonist saclofen (5nmol) injected into the LPBN did not change the effects of moxonidine on 0.3M NaCl intake (24.3±7.8ml/120min). These results suggest that the increase of 0.3M NaCl intake by α2-adrenergic receptor activation in the LPBN is partially dependent on GABAA and opioid receptor activation in this area.

Oligopeptidases B from Trypanossoma cruzi and Trypanossoma brucei Inhibit Inflammatory Pain in Mice by Targeting Serotoninergic Receptors

In the present study, the antinociceptive profile of oligopeptidases B from Trypanosoma cruzi (OPTc) and Trypanosoma brucei (OPTb) were examined in mice evaluated by the acetic acid-induced writhing test. Both OPTc and OPTb injected intraperitoneally attenuated the writhing numbers in the acetic acid-induced writhing test. This effect was not dependent on the enzymatic activity, but the enzyme structure was important for this purpose. Intraperitoneal pretreatment with methysergide (5-HT serotonergic receptor antagonist) attenuated antinociceptive effect induced by both OPTc and OPTb in the writhing test. However, naloxone (opioid receptor antagonist) or yohimbine (α2-adrenergic receptor antagonist) did not affect antinociception induced by both oligopeptidases. Our results suggest that OPTc and OPTb show antinociceptive property in the writhing test. Furthermore, this antinociceptive effect may be mediated by serotonergic receptor but not opioidergic or α2-adrenergic receptors.