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A Low Dose of Naloxone Added to Ropivacaine Prolongs Femoral Nerve Blockade: A Randomized Clinical Trial. Pain Res Manag 2021; 2021:6639009. [PMID: 33603939 PMCID: PMC7868154 DOI: 10.1155/2021/6639009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/24/2020] [Accepted: 01/20/2021] [Indexed: 11/18/2022]
Abstract
Femoral nerve blocks (FNBs) are used as safe and useful procedures to control severe postoperative pain from total knee arthroplasty (TKA). Various adjuvants have been used to prolong the duration of the local anesthetic blockade. This study evaluated whether a low dose of naloxone administered with local anesthetics prolongs the duration of FNB. A prospective, randomized double-blind controlled study was conducted with 74 patients undergoing unilateral TKA. Through a single-bolus administration guided by ultrasound, the control group (group C) received 20 mL of 0.375% ropivacaine, while the naloxone group (group N) received 20 mL of 0.375% ropivacaine with 100 ng of naloxone. The time elapsed before the first analgesia request, the total amount of opioids consumed at 24 h postoperatively, the onset time of the sensory blockade, the visual analog pain scale (VAS) scores after arriving at the recovery room, after 6, 12, 18, and 24 h at rest and after 12, 18, and 24 h of activity, the quadricep strength before the FNB procedure and at 12 and 24 h postoperatively, the quality of sleep on the first night after surgery, the satisfaction score, and the incidence of postoperative complications were recorded. The time elapsed before the first analgesia request was significantly longer in group N (735.5 ± 187.2 min) than that in group C (602.6 ± 210.4 min) (P=0.003). The total dose of supplementary opioids consumed at 24 h postoperatively was significantly lower in group N (312.4 ± 141.7 μg) than that in group C (456.5 ± 279.5 μg) (P=0.007). Lower VAS scores were recorded in group N than that in group C at rest and during knee activity (rest, 12 h, P=0.001, 18 h, P=0.043; activity, 12 h, P=0.001). The addition of a low dose of naloxone to ropivacaine for FNB significantly delayed the first request for rescue analgesia and decreased the opioid consumption within 24 h, without significant complications.
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Wells RE, Collier J, Posey G, Morgan F, Auman T, Strittameter B, Magalhaes R, Adler-Neal A, McHaffie JG, Zeidan F. Attention to breath sensations does not engage endogenous opioids to reduce pain. Pain 2020; 161:1884-1893. [PMID: 32701847 PMCID: PMC7483215 DOI: 10.1097/j.pain.0000000000001865] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The endogenous opioidergic system is critically involved in the cognitive modulation of pain. Slow-breathing-based techniques are widely used nonpharmacological approaches to reduce pain. Yet, the active mechanisms of actions supporting these practices are poorly characterized. Growing evidence suggest that mindfulness-meditation, a slow-breathing technique practiced by nonreactively attending to breathing sensations, engages multiple unique neural mechanisms that bypass opioidergically mediated descending pathways to reduce pain. However, it is unknown whether endogenous opioids contribute to pain reductions produced by slow breathing. The present double-blind, placebo-controlled crossover study examined behavioral pain responses during mindfulness-meditation (n = 19), sham-mindfulness meditation (n = 20), and slow-paced breathing (n = 20) in response to noxious heat (49°C) and intravenous administration (0.15 mg/kg bolus + 0.1 mg/kg/hour maintenance infusion) of the opioid antagonist, naloxone, and placebo saline. Mindfulness significantly reduced pain unpleasantness ratings across both infusion sessions when compared to rest, but not pain intensity. Slow-paced breathing significantly reduced pain intensity and unpleasantness ratings during naloxone but not saline infusion. Pain reductions produced by mindfulness-meditation and slow-paced breathing were insensitive to naloxone when compared to saline administration. By contrast, sham-mindfulness meditation produced pain unpleasantness reductions during saline infusion but this effect was reversed by opioidergic antagonism. Sham-mindfulness did not lower pain intensity ratings. Self-reported "focusing on the breath" was identified as the operational feature particularly unique to the mindfulness-meditation and slow paced-breathing, but not sham-mindfulness meditation. Across all individuals, attending to the breath was associated with naloxone insensitive pain-relief. These findings provide evidence that slow breathing combined with attention to breath reduces pain independent of endogenous opioids.
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Affiliation(s)
| | - Jason Collier
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine
| | - Grace Posey
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine
| | - Fry Morgan
- Department of Psychiatry, Wake Forest School of Medicine
| | - Timothy Auman
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine
| | | | - Rossana Magalhaes
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine
| | | | - John G. McHaffie
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine
| | - Fadel Zeidan
- Department of Anesthesiology, University of California San Diego
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Systemic administration of low-dose naltrexone increases bone mass due to blockade of opioid growth factor receptor signaling in mice osteoblasts. Life Sci 2019; 224:232-240. [DOI: 10.1016/j.lfs.2019.03.069] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/14/2019] [Accepted: 03/27/2019] [Indexed: 01/31/2023]
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Pineda-Farias JB, Caram-Salas NL, Salinas-Abarca AB, Ocampo J, Granados-Soto V. Ultra-Low Doses of Naltrexone Enhance the Antiallodynic Effect of Pregabalin or Gabapentin in Neuropathic Rats. Drug Dev Res 2017; 78:371-380. [PMID: 28868795 DOI: 10.1002/ddr.21409] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/14/2017] [Indexed: 11/06/2022]
Abstract
Preclinical Research Treatment of neuropathic pain is an area of largely unmet medical need. Pregabalin and gabapentin are anticonvulsants widely used for the treatment of neuropathic pain. Unfortunately, these drugs are only effective in 50-60% of the treated patients. In addition, both drugs have substantial side effects. Several studies have reported that ultralow doses of opioid receptor antagonists can induce analgesia and enhance the analgesic effect of opioids in rodents and humans. The objective of the present study was to assess the antiallodynic synergistic interaction between gabapentinoids and naltrexone in rats. Oral administration of pregabalin (ED50 = 2.79 ± 0.16 mg/kg) or gabapentin (ED50 = 21.04 ± 2.87 mg/kg) as well as intrathecal naltrexone (ED50 = 0.11 ± 0.02 ng) reduced in a dose-dependent manner tactile allodynia in rats. Maximal antiallodynic effects (∼100%) were reached with 30 mg/kg of pregabalin, 300 mg/kg of gabapentin or 0.5 ng of naltrexone. Co-administration of pregabalin or gabapentin and naltrexone in a fixed-dose ratio (1:1) remarkably reduced spinal nerve ligation-induced tactile allodynia showing a synergistic interaction. The data indicate that combinations of pregabalin or gabapentin and ultra-low doses of naltrexone are able to reduce tactile allodynia in neuropathic rats with lower doses that those used when drugs are given individually and with an improved side effects profile. Drug Dev Res 78 : 371-380, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Jorge B Pineda-Farias
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Unidad Coapa Calzada de los Tenorios 235, Col. Granjas Coapa, Tlalpan, 14330, Ciudad de México, Mexico
| | - Nadia L Caram-Salas
- Catedra Conacyt, Estudios Moleculares Avanzados, Instituto de Ecología AC (INECOL). Carretera antigua a Coatepec 351, El Haya, Xalapa, Veracruz, Mexico
| | - Ana B Salinas-Abarca
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Unidad Coapa Calzada de los Tenorios 235, Col. Granjas Coapa, Tlalpan, 14330, Ciudad de México, Mexico
| | - Jorge Ocampo
- Laboratorio Médico Químico Biológico S.A. de C.V. (Bioquimed), Ciudad de México, Mexico
| | - Vinicio Granados-Soto
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Unidad Coapa Calzada de los Tenorios 235, Col. Granjas Coapa, Tlalpan, 14330, Ciudad de México, Mexico
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Abstract
UNLABELLED Mindfulness meditation, a cognitive practice premised on sustaining nonjudgmental awareness of arising sensory events, reliably attenuates pain. Mindfulness meditation activates multiple brain regions that contain a high expression of opioid receptors. However, it is unknown whether mindfulness-meditation-based analgesia is mediated by endogenous opioids. The present double-blind, randomized study examined behavioral pain responses in healthy human volunteers during mindfulness meditation and a nonmanipulation control condition in response to noxious heat and intravenous administration of the opioid antagonist naloxone (0.15 mg/kg bolus + 0.1 mg/kg/h infusion) or saline placebo. Meditation during saline infusion significantly reduced pain intensity and unpleasantness ratings when compared to the control + saline group. However, naloxone infusion failed to reverse meditation-induced analgesia. There were no significant differences in pain intensity or pain unpleasantness reductions between the meditation + naloxone and the meditation + saline groups. Furthermore, mindfulness meditation during naloxone produced significantly greater reductions in pain intensity and unpleasantness than the control groups. These findings demonstrate that mindfulness meditation does not rely on endogenous opioidergic mechanisms to reduce pain. SIGNIFICANCE STATEMENT Endogenous opioids have been repeatedly shown to be involved in the cognitive inhibition of pain. Mindfulness meditation, a practice premised on directing nonjudgmental attention to arising sensory events, reduces pain by engaging mechanisms supporting the cognitive control of pain. However, it remains unknown if mindfulness-meditation-based analgesia is mediated by opioids, an important consideration for using meditation to treat chronic pain. To address this question, the present study examined pain reports during meditation in response to noxious heat and administration of the opioid antagonist naloxone and placebo saline. The results demonstrate that meditation-based pain relief does not require endogenous opioids. Therefore, the treatment of chronic pain may be more effective with meditation due to a lack of cross-tolerance with opiate-based medications.
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Vance CG, Rakel BA, Dailey DL, Sluka KA. Skin impedance is not a factor in transcutaneous electrical nerve stimulation effectiveness. J Pain Res 2015; 8:571-80. [PMID: 26316808 PMCID: PMC4547643 DOI: 10.2147/jpr.s86577] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological intervention used to manage pain using skin surface electrodes. Optimal electrode placement is unclear. We hypothesized that better analgesia would occur if electrodes were placed over sites with lower skin impedance. Optimal site selection (OSS) and sham site selection (SSS) electrode sites on the forearm were identified using a standard clinical technique. METHODS Experiment 1 measured skin impedance in the forearm at OSS and SSS. Experiment 2 was a crossover design double-blind randomized controlled trial comparing OSS-TENS, SSS-TENS, and placebo TENS (P-TENS) to confirm differences in skin impedance between OSS and SSS, and measure change in pressure pain threshold (PPT) following a 30-minute TENS treatment. Healthy volunteers were recruited (ten for Experiment 1 [five male, five female] and 24 for Experiment 2 [12 male, 12 female]). TENS was applied for 30 minutes at 100 Hz frequency, 100 µs pulse duration, and "strong but nonpainful" amplitude. RESULTS Experiment 1 results demonstrate significantly higher impedance at SSS (17.69±1.24 Ω) compared to OSS (13.53±0.57 Ω) (P=0.007). For Experiment 2, electrode site impedance was significantly higher over SSS, with both the impedance meter (P=0.001) and the TENS unit (P=0.012) compared to OSS. PPT change was significantly greater for both OSS-TENS (P=0.024) and SSS-TENS (P=0.025) when compared to P-TENS. PPT did not differ between the two active TENS treatments (P=0.81). CONCLUSION Skin impedance is lower at sites characterized as optimal using the described technique of electrode site selection. When TENS is applied at adequate intensities, skin impedance is not a factor in attainment of hypoalgesia of the forearm in healthy subjects. Further investigation should include testing in patients presenting with painful conditions.
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Affiliation(s)
- Carol Gt Vance
- Department of Physical Therapy and Rehabilitation Science, University of Iowa Carver College of Medicine, IA, USA
| | - Barbara A Rakel
- Department of Physical Therapy and Rehabilitation Science, University of Iowa Carver College of Medicine, IA, USA ; University of Iowa, College Nursing Iowa City, IA, USA
| | - Dana L Dailey
- Department of Physical Therapy and Rehabilitation Science, University of Iowa Carver College of Medicine, IA, USA
| | - Kathleen A Sluka
- Department of Physical Therapy and Rehabilitation Science, University of Iowa Carver College of Medicine, IA, USA ; University of Iowa, College Nursing Iowa City, IA, USA
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Marashi SM, Sharifnia HR, Azimaraghi O, Aghajani Y, Barzin G, Movafegh A. Naloxone added to bupivacaine or bupivacaine-fentanyl prolongs motor and sensory block during supraclavicular brachial plexus blockade: a randomized clinical trial. Acta Anaesthesiol Scand 2015; 59:921-7. [PMID: 25922978 DOI: 10.1111/aas.12527] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 02/16/2015] [Accepted: 03/09/2015] [Indexed: 01/12/2023]
Abstract
BACKGROUND In this study, the effect of naloxone on duration of supraclavicular brachial plexus block was evaluated. It was hypothesized that naloxone can increase the duration of neural blockade. METHODS Sixty-eight patients scheduled for surgery under supraclavicular brachial plexus block were randomly assigned to receive 30 ml bupivacaine (Group C); 30 ml bupivacaine with 100 μg of fentanyl (Group F); 30 ml bupivacaine with 100 ng naloxone (Group N); or 30 ml bupivacaine with 100 μg of fentanyl and 100 ng naloxone (Group N + F). Sensory and motor blockade were recorded at 5, 15, and 30 min following the block, and every 10 min following the end of surgery. Duration of sensory and motor block was considered to be the time interval between the complete block and the first postoperative pain and complete recovery of motor functions. RESULTS Sensory and motor onset times were the same in all groups. The duration of sensory and motor block in Group C (11.3 ± 1.7 h and 4.56 ± 1.0 h) and Group F (12.8 ± 3.3 h and 5.1 ± 2.0 h) were less than in the other groups (18.1 ± 2.2 h and 6.18 ± 1.0 h in Group N, and 15.8 ± 2.9 h and 6.53 ± 1.1 h in Group N + F, P < 0.0001). CONCLUSION Addition of naloxone to bupivacaine in supraclavicular brachial plexus block prolonged the duration of the neural blockade.
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Affiliation(s)
- S. M. Marashi
- Department of Anesthesiology; Shariati Hospital; Tehran University of Medical Sciences; Tehran Iran
| | - H. R. Sharifnia
- Department of Anesthesiology; Shariati Hospital; Tehran University of Medical Sciences; Tehran Iran
| | - O. Azimaraghi
- Department of Anesthesiology; Shariati Hospital; Tehran University of Medical Sciences; Tehran Iran
| | - Y. Aghajani
- Department of Anesthesiology; Shariati Hospital; Tehran University of Medical Sciences; Tehran Iran
| | - G. Barzin
- Department of Anesthesiology; Shariati Hospital; Tehran University of Medical Sciences; Tehran Iran
| | - A. Movafegh
- Department of Anesthesiology; Shariati Hospital; Tehran University of Medical Sciences; Tehran Iran
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Werner MU, Pereira MP, Andersen LPH, Dahl JB. Endogenous opioid antagonism in physiological experimental pain models: a systematic review. PLoS One 2015; 10:e0125887. [PMID: 26029906 PMCID: PMC4452333 DOI: 10.1371/journal.pone.0125887] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Accepted: 03/23/2015] [Indexed: 12/11/2022] Open
Abstract
Opioid antagonists are pharmacological tools applied as an indirect measure to detect activation of the endogenous opioid system (EOS) in experimental pain models. The objective of this systematic review was to examine the effect of mu-opioid-receptor (MOR) antagonists in placebo-controlled, double-blind studies using ʻinhibitoryʼ or ʻsensitizingʼ, physiological test paradigms in healthy human subjects. The databases PubMed and Embase were searched according to predefined criteria. Out of a total of 2,142 records, 63 studies (1,477 subjects [male/female ratio = 1.5]) were considered relevant. Twenty-five studies utilized ʻinhibitoryʼ test paradigms (ITP) and 38 studies utilized ʻsensitizingʼ test paradigms (STP). The ITP-studies were characterized as conditioning modulation models (22 studies) and repetitive transcranial magnetic stimulation models (rTMS; 3 studies), and, the STP-studies as secondary hyperalgesia models (6 studies), ʻpainʼ models (25 studies), summation models (2 studies), nociceptive reflex models (3 studies) and miscellaneous models (2 studies). A consistent reversal of analgesia by a MOR-antagonist was demonstrated in 10 of the 25 ITP-studies, including stress-induced analgesia and rTMS. In the remaining 14 conditioning modulation studies either absence of effects or ambiguous effects by MOR-antagonists, were observed. In the STP-studies, no effect of the opioid-blockade could be demonstrated in 5 out of 6 secondary hyperalgesia studies. The direction of MOR-antagonist dependent effects upon pain ratings, threshold assessments and somatosensory evoked potentials (SSEP), did not appear consistent in 28 out of 32 ʻpainʼ model studies. In conclusion, only in 2 experimental human pain models, i.e., stress-induced analgesia and rTMS, administration of MOR-antagonist demonstrated a consistent effect, presumably mediated by an EOS-dependent mechanisms of analgesia and hyperalgesia.
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Affiliation(s)
- Mads U. Werner
- Multidisciplinary Pain Center, Neuroscience Center, Rigshospitalet, Copenhagen, Denmark
- * E-mail:
| | - Manuel P. Pereira
- Multidisciplinary Pain Center, Neuroscience Center, Rigshospitalet, Copenhagen, Denmark
- Department of Anaesthesia, Centre of Head and Orthopaedics, Rigshospitalet, Copenhagen, Denmark
| | | | - Jørgen B. Dahl
- Department of Anaesthesia, Centre of Head and Orthopaedics, Rigshospitalet, Copenhagen, Denmark
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Abstract
The use of oral sucrose has been the most extensively studied pain intervention in newborn care to date. More than 150 published studies relating to sweet-taste-induced calming and analgesia in human infants have been identified, of which 100 (65%) include sucrose. With only a few exceptions, sucrose, glucose, or other sweet solutions reduced pain responses during commonly performed painful procedures in diverse populations of infants up to 12 months of age. Sucrose has been widely recommended for routine use during painful procedures in newborn and young infants, yet these recommendations have not been translated into consistent use in clinical practice. One reason may be related to important knowledge and research gaps concerning analgesic effects of sucrose. Notably, the mechanism of sweet-taste-induced analgesia is still not precisely understood, which has implications for using research evidence in practice. The aim of this article is to review what is known about the mechanisms of sucrose-induced analgesia; highlight existing evidence, knowledge gaps, and current controversies; and provide directions for future research and practice.
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Affiliation(s)
- Denise Harrison
- Centre for Practice Changing Research, Children’s Hospital of Eastern Ontario, Ottawa, Canada.
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MOVAFEGH A, SHOEIBI G, ANSARI M, SADEGHI M, AZIMARAGHI O, AGHAJANI Y. Naloxone infusion and post-hysterectomy morphine consumption: a double-blind, placebo-controlled study. Acta Anaesthesiol Scand 2012; 56:1241-9. [PMID: 22946762 DOI: 10.1111/j.1399-6576.2012.02764.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2012] [Indexed: 01/18/2023]
Abstract
BACKGROUND The evidence that an infusion of a low dose of naloxone reduces post-operative pain and opioid analgesic consumption is somewhat conflicting. Thus, the aim of the present study was to investigate the effect of an ultra-low dose of naloxone on patient-controlled morphine analgesia. METHODS Ninety patients, 35-55 years old, scheduled for total abdominal hysterectomy, were enrolled in this prospective, randomized, double-blind and placebo-controlled study. Post-operatively, they received either saline (n = 45) or naloxone (n = 45) for 24 h. A standard general anesthesia was administered in both groups. In the recovery room, patients received morphine by a patient-controlled analgesia device. An ultra-low dose of naloxone was infused intravenously at 0.25 μg/kg/h for 24 h in the intervention group. Saline was infused in the control group. Following the surgery, morphine consumption, numeric rating score for pain intensity, nausea and vomiting, pruritus, and requests for antiemetic were recorded at baseline, 30 min, 1, 4, 8,16, 20, and 24 h following their discharge from recovery. RESULTS Naloxone reduced morphine consumption over the first 24 post-operative hours significantly compared with the controls (saline) {19.5 [standard deviation (SD) 3.4] mg vs. 27.5 [SD 5.9] mg; P < 0.001}. The incidence and severity of nausea and vomiting was significantly reduced in the naloxone group. The incidence of pruritus and the pain scores at rest and activity were not significantly different. CONCLUSION Following hysterectomy, an ultra-low dose of naloxone infusion proved to reduce morphine consumption as well as the incidence and severity of opioid-induced nausea and vomiting.
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Affiliation(s)
- A. MOVAFEGH
- Department of Anesthesiology, Pain and Critical Care; Dr Ali Shariati Hospital, Tehran University of Medical Sciences; Tehran; Iran
| | - G. SHOEIBI
- Department of Anesthesiology, Pain and Critical Care; Dr Ali Shariati Hospital, Tehran University of Medical Sciences; Tehran; Iran
| | - M. ANSARI
- Development Research Center; Dr Ali Shariati Hospital, Tehran University of Medical Sciences; Tehran; Iran
| | - M. SADEGHI
- Department of Anesthesiology, Pain and Critical Care; Dr Ali Shariati Hospital, Tehran University of Medical Sciences; Tehran; Iran
| | - O. AZIMARAGHI
- Department of Anesthesiology, Pain and Critical Care; Dr Ali Shariati Hospital, Tehran University of Medical Sciences; Tehran; Iran
| | - Y. AGHAJANI
- Department of Anesthesiology, Pain and Critical Care; Dr Ali Shariati Hospital, Tehran University of Medical Sciences; Tehran; Iran
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Effects of transcutaneous electrical nerve stimulation on pain, pain sensitivity, and function in people with knee osteoarthritis: a randomized controlled trial. Phys Ther 2012; 92:898-910. [PMID: 22466027 PMCID: PMC3386514 DOI: 10.2522/ptj.20110183] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Transcutaneous electrical nerve stimulation (TENS) is commonly used for the management of pain; however, its effects on several pain and function measures are unclear. OBJECTIVE The purpose of this study was to determine the effects of high-frequency TENS (HF-TENS) and low-frequency TENS (LF-TENS) on several outcome measures (pain at rest, movement-evoked pain, and pain sensitivity) in people with knee osteoarthritis. DESIGN The study was a double-blind, randomized clinical trial. SETTING The setting was a tertiary care center. PARTICIPANTS Seventy-five participants with knee osteoarthritis (29 men and 46 women; 31-94 years of age) were assessed. INTERVENTION Participants were randomly assigned to receive HF-TENS (100 Hz) (n=25), LF-TENS (4 Hz) (n=25), or placebo TENS (n=25) (pulse duration=100 microseconds; intensity=10% below motor threshold). MEASUREMENTS The following measures were assessed before and after a single TENS treatment: cutaneous mechanical pain threshold, pressure pain threshold (PPT), heat pain threshold, heat temporal summation, Timed "Up & Go" Test (TUG), and pain intensity at rest and during the TUG. A linear mixed-model analysis of variance was used to compare differences before and after TENS and among groups (HF-TENS, LF-TENS, and placebo TENS). RESULTS Compared with placebo TENS, HF-TENS and LF-TENS increased PPT at the knee; HF-TENS also increased PPT over the tibialis anterior muscle. There was no effect on the cutaneous mechanical pain threshold, heat pain threshold, or heat temporal summation. Pain at rest and during the TUG was significantly reduced by HF-TENS, LF-TENS, and placebo TENS. LIMITATIONS This study tested only a single TENS treatment. CONCLUSIONS Both HF-TENS and LF-TENS increased PPT in people with knee osteoarthritis; placebo TENS had no significant effect on PPT. Cutaneous pain measures were unaffected by TENS. Subjective pain ratings at rest and during movement were similarly reduced by active TENS and placebo TENS, suggesting a strong placebo component of the effect of TENS.
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Opioid-independent mechanisms supporting offset analgesia and temporal sharpening of nociceptive information. Pain 2012; 153:1232-1243. [PMID: 22503222 DOI: 10.1016/j.pain.2012.02.035] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2011] [Revised: 02/24/2012] [Accepted: 02/24/2012] [Indexed: 11/22/2022]
Abstract
The mechanisms supporting temporal processing of pain remain poorly understood. To determine the involvement of opioid mechanisms in temporal processing of pain, responses to dynamic noxious thermal stimuli and offset analgesia were assessed after administration of naloxone, a μ-opioid antagonist, and on a separate day, during and after intravenous administration of remifentanil, a μ-opioid agonist, in 19 healthy human volunteers. Multiple end points were sampled from real-time computerized visual analog scale ratings (VAS, 1 to 10) to assess thermal sensitivity, magnitude and duration of offset analgesia, and painful after sensations. It was hypothesized that the magnitude of offset analgesia would be reduced by direct opioid antagonism and during states of acute opioid-induced hypersensitivity (OIH), as well as diminished by the presence of exogenous opioids. Surprisingly, the magnitude of offset analgesia was not altered after naloxone administration, during remifentanil infusion, or after the termination of remifentanil infusion. Because thermal hyperalgesia was observed after both drugs, 8 of the original 19 subjects returned for an additional session without drug administration. Thermal hyperalgesia and increased magnitude of offset analgesia were observed across conditions of remifentanil, naloxone, and no drug within this subset analysis, indicating that repeated heat testing induced thermal hyperalgesia, which potentiated the magnitude of offset analgesia. Thus, it is concluded that the mechanisms subserving temporal processing of nociceptive information are largely opioid-independent, but that offset analgesia may be potentiated by heat-induced thermal hyperalgesia in a proportion of individuals.
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Movafegh A, Nouralishahi B, Sadeghi M, Nabavian O. An ultra-low dose of naloxone added to lidocaine or lidocaine-fentanyl mixture prolongs axillary brachial plexus blockade. Anesth Analg 2009; 109:1679-83. [PMID: 19843808 DOI: 10.1213/ane.0b013e3181b9e904] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION In this prospective, randomized, double-blind study, we evaluated the effect of an ultra-low dose of naloxone added to lidocaine and fentanyl mixture on the onset and duration of axillary brachial plexus block. METHODS One hundred twelve patients scheduled for elective forearm surgery under axillary brachial plexus block were randomly allocated to receive 34 mL lidocaine 1.5% with 3 mL of isotonic saline chloride (control group, n = 28), 34 mL lidocaine 1.5% with 2 mL (100 microg) of fentanyl and 1 mL of isotonic saline chloride (fentanyl group, n = 28), 34 mL lidocaine 1.5% with 2 mL saline chloride and 100 ng (1 mL) naloxone (naloxone group, n = 28), or 34 mL lidocaine 1.5% with 2 mL (100 microg) of fentanyl and 100 ng (1 mL) naloxone (naloxone + fentanyl group, n = 28). A multiple stimulation technique was used in all patients. After performing the block, sensory and motor blockades of radial, median, musculocutaneous, and ulnar nerves were recorded at 5, 15, and 30 min. The onset time of the sensory and motor blockades was defined as the time between the last injection and the total abolition of the pinprick response and complete paralysis, respectively. The duration of sensory and motor blocks was considered as the time interval between the complete block and the first postoperative pain and complete recovery of motor functions. RESULTS Sensory and motor onset times were longer in the naloxone (sensory onset time: 15 +/- 3, and motor onset time: 21 +/- 4) and naloxone + fentanyl group than control or fentanyl groups (sensory onset time: 10 +/- 3 min in control group, 10 +/- 4 min in fentanyl group, and 17 +/- 3 min in naloxone + fentanyl group, motor onset time: 15 +/- 5 min in control group, 14 +/- 7 min in fentanyl group, and 17.3 +/- 3.4 min in naloxone + fentanyl group) (P < 0.001). The duration of time to first postoperative pain and motor blockade was significantly longer in the naloxone (92 +/- 10 and 115 +/- 10 min) and naloxone + fentanyl groups (98 +/- 12 and 122 +/- 16 min) than control (68 +/- 7 and 89 +/- 11 min) and fentanyl groups (68 +/- 11 and 90 +/- 12 min) (P < 0.001). The time to first postoperative pain was significantly longer in the naloxone and naloxone + fentanyl groups than in the control or fentanyl groups (P < 0.001). CONCLUSIONS The addition of an ultra-low dose of naloxone to lidocaine 1.5% solution with or without fentanyl solution in axillary brachial plexus block prolongs the time to first postoperative pain and motor blockade but also lengthens the onset time.
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Affiliation(s)
- Ali Movafegh
- Department of Anesthesiology and Critical Care, Dr Ali Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
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14
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Slover R, Coy J, Davids HR. Advances in the management of pain in children: acute pain. Adv Pediatr 2009; 56:341-58. [PMID: 19968955 DOI: 10.1016/j.yapd.2009.08.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Robin Slover
- The Children's Hospital, Chronic Pain Clinic, Aurora, CO, USA.
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15
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Petrizzi L, Mariscoli M, Valbonetti L, Varasano V, Langhoff JD, Von Rechenberg B. Preliminary study on the effect of parenteral naloxone, alone and in association with calcium gluconate, on bone healing in an ovine "drill hole" model system. BMC Musculoskelet Disord 2007; 8:43. [PMID: 17518998 PMCID: PMC1891106 DOI: 10.1186/1471-2474-8-43] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2006] [Accepted: 05/22/2007] [Indexed: 12/27/2022] Open
Abstract
Background Several diseases affect bone healing and physiology. Many drugs that are commonly used in orthopaedics as "analgesics" or anti-inflammatory agents impair bone healing. Stressful conditions are associated with decreased serum osteocalcin concentration. High endorphin levels alter calcium metabolism, blocking the membrane channels by which calcium normally enters cells. The consequent decrease of intracellular calcium impairs the activities of calcium-related enzymes. Naloxone is a pure opioid antagonist. Morphine-induced osteocalcin inhibition was abolished when osteoblasts were incubated with naloxone. Naloxone restored the altered cellular and tissue physiology by removing β-endorphins from specific receptors. However, this is only possible if the circulating Ca concentration is adequate. The aim of the present study was to evaluate the efficacy of parenteral naloxone administration in inducing fast mineralization and callus remodelling in a group of sheep with a standardised bone lesion. Methods Twenty ewes were randomly assigned to 4 treatment groups. Group A acted as control, group B received a solution of calcium gluconate, group C a solution of naloxone, and group D a solution of calcium gluconate and naloxone. A transverse hole was drilled in the left metacarpus, including both cortices, then parenteral treatment was administered intramuscularly, daily for four weeks. Healing was evaluated by weekly radiographic examination for eight weeks. For quantitative evaluation, the ratio of the radiographic bone density between the drill area and the adjacent cortical bone was calculated. After eight weeks the sheep were slaughtered and a sample of bone was collected for histopathology Results Group D showed a higher radiographic ratio than the other groups. Sheep not treated with naloxone showed a persistently lower ratio in the lateral than the medial cortex (P < 0.01). Histopathology of bone samples showed more caverns and fewer osteoblasts in group D than in the other groups (P ≤ 0.001). Conclusion A low-dose parenteral regimen of naloxone enhances mineralization and remodelling of the callus in healing cortical defects in sheep, especially if associated with calcium gluconate.
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Affiliation(s)
- Lucio Petrizzi
- Department of Veterinary Clinical Sciences – University of Teramo, Italy
| | - Massimo Mariscoli
- Department of Veterinary Clinical Sciences – University of Teramo, Italy
| | - Luca Valbonetti
- Department of Veterinary Clinical Sciences – University of Teramo, Italy
| | - Vincenzo Varasano
- Department of Veterinary Clinical Sciences – University of Teramo, Italy
| | - Jens D Langhoff
- Musculoskeletal Research Unit – Vetsuisse University of Zürich, Zürich, Switzerland
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16
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Mannelli P, Gottheil E, Van Bockstaele EJ. Antagonist treatment of opioid withdrawal translational low dose approach. J Addict Dis 2007; 25:1-8. [PMID: 16785213 DOI: 10.1300/j069v25n02_01] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Although antagonist drugs are receiving increasing attention in the treatment of opioid withdrawal, the mechanisms of interaction of opiate agonists and antagonists remain largely to be investigated. We focused on the effects of very low quantities of opiate antagonists, following the clinical indication of their potential utility in detoxification. Upon reviewing the evidence on the administration of small doses of naloxone and naltrexone in the presence of agonist drugs, the effects of low-dose naltrexone during opiate administration and withdrawal are described. The application of a translational methodology allowed completing the clinical design with behavioral and cellular information obtained from a specifically developed animal model. The initial results indicate that low doses of naltrexone may help reducing the manifestation of opioid withdrawal, offer suggestions for further investigations and confirm the utility of a translational research approach to the clinical neurobiology of drug addiction.
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Affiliation(s)
- Paolo Mannelli
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27704, USA.
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17
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Roscoe JA, Jean-Pierre P, Shelke AR, Kaufman ME, Bole C, Morrow GR. The role of patients' response expectancies in side effect development and control. Curr Probl Cancer 2006; 30:40-98. [PMID: 16516693 DOI: 10.1016/j.currproblcancer.2005.12.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Joseph A Roscoe
- Department of Radiation Oncology, University of Rochester, James P. Wilmot Cancer Center, Rochester, New York, USA
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18
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Fudala PJ, Johnson RE. Development of opioid formulations with limited diversion and abuse potential. Drug Alcohol Depend 2006; 83 Suppl 1:S40-7. [PMID: 16564141 DOI: 10.1016/j.drugalcdep.2006.01.016] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 12/27/2005] [Accepted: 01/02/2006] [Indexed: 10/24/2022]
Abstract
Non-medical abuse of prescription opioid medications is not a new phenomenon, but such use has been increasing in recent years. Various methods have been used and continue to be developed in an effort to limit diversion and abuse of opioid medications. A number of these methods will be described for opioid analgesic and addiction treatment formulations using relevant historical examples (e.g. propoxyphene, pentazocine, buprenorphine) as well as examples of formulations currently being considered or under development (e.g. oxycodone plus naltrexone, sustained-release buprenorphine). The focus, though not exclusively, will be on those formulations that represent a combination of an opioid agonist with an antagonist. These methods must take into consideration the pharmacokinetic profile of the agonist and antagonist, the expected primary route of abuse of the medication and the medication combination, the dose of medication that is likely to be abused, the availability of alternative drugs of abuse, and the population of potential abusers that is being targeted with the revised formulation.
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Affiliation(s)
- Paul J Fudala
- Behavioral Health Service, VA Medical Center and the Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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19
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Van Bockstaele EJ, Rudoy C, Mannelli P, Oropeza V, Qian Y. Elevated μ-opioid receptor expression in the nucleus of the solitary tract accompanies attenuated withdrawal signs after chronic low dose naltrexone in opiate-dependent rats. J Neurosci Res 2006; 83:508-14. [PMID: 16385558 DOI: 10.1002/jnr.20738] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We previously described a decrease in withdrawal behaviors in opiate-dependent rats that were chronically treated with very low doses of naltrexone in their drinking water. Attenuated expression of withdrawal behaviors correlated with decreased c-Fos expression and intracellular signal transduction elements [protein kinase A regulatory subunit II (PKA) and phosphorylated cAMP response element binding protein (pCREB)] in brainstem noradrenergic nuclei. In this study, to determine whether similar cellular changes occurred in forebrain nuclei associated with drug reward, expressions of PKA and pCREB were analyzed in the ventral tegmental area, frontal cortex, striatum, and amygdala of opiate-treated rats that received low doses of naltrexone in their drinking water. No significant difference in PKA or pCREB was detected in these regions following drug treatment. To examine further the cellular mechanisms in noradrenergic nuclei that could underlie attenuated withdrawal behaviors following low dose naltrexone administration, the nucleus of the solitary tract (NTS) and locus coeruleus (LC) were examined for opioid receptor (OR) protein expression. Results showed a significant increase in muOR expression in the NTS of morphine-dependent rats that received low doses of naltrexone in their drinking water, and increases in muOR expression were also found to be dose dependent. Protein expression of muOR in the LC and deltaOR in either brain region remained unchanged. In conclusion, our previously reported decreases in c-Fos and PKA expression in the NTS following pretreatment with low doses of naltrexone may be partially explained by a greater inhibition of NTS neurons resulting from increased muOR expression in this region.
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Affiliation(s)
- E J Van Bockstaele
- Department of Neurosurgery, Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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20
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Bang SR, Kim HS, Kim JH, Sim WS, Gwak MS, Yang MK, Kim CS, Hahm TS, Cho HS, Choi DH, Kim TH. Effects of Epidural Naloxone on Pruritus Induced by Hydromorphone Epidural Patient-Controlled Analgesia. Korean J Pain 2006. [DOI: 10.3344/kjp.2006.19.1.91] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Si Ra Bang
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Hee Suk Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ji Hyeok Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Woo Seok Sim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Mi Sook Gwak
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Mi Kyung Yang
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Chung Su Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Tae Soo Hahm
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Hyun Sung Cho
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Duck Hwan Choi
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Tae Hyeong Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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21
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Mannelli P, Gottheil E, Peoples JF, Oropeza VC, Van Bockstaele EJ. Chronic very low dose naltrexone administration attenuates opioid withdrawal expression. Biol Psychiatry 2004; 56:261-8. [PMID: 15312814 DOI: 10.1016/j.biopsych.2004.05.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 04/22/2004] [Accepted: 05/26/2004] [Indexed: 11/18/2022]
Abstract
BACKGROUND Different regimens of agonist and antagonist drugs have been used in opioid withdrawal management, with variable results. We examined whether administering extremely small quantities of opiate antagonists in the presence of opiate agonist drugs reduces withdrawal expression. METHODS Forty-one male Sprague-Dawley rats were implanted with morphine or placebo pellets for eight days. Starting on day 3, some rats received naltrexone in their drinking water (5 mg/L), or unadulterated water. On day 8, rats were injected with saline or naltrexone (100 mg/kg) and evaluated for behavioral signs of withdrawal. Next, sections through the locus coeruleus (LC) and nucleus of the solitary tract (NTS), brainstem areas exhibiting cellular activation following opiate withdrawal, were processed for c-Fos to detect early gene expression. Finally, the same nuclei were examined for protein kinase A regulatory subunit II (PKA) and phosphorylated cyclic adenosine monophosphate response element binding protein (pCREB), using Western blot analysis. RESULTS Withdrawal was attenuated and c-Fos, PKA, and pCREB expression was decreased in the NTS and LC of rats receiving chronic very low doses of naltrexone. CONCLUSIONS Reduction of withdrawal upon chronic very low naltrexone administration may be due in part to decreased activation of brainstem noradrenergic neurons in morphine dependent rats.
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Affiliation(s)
- Paolo Mannelli
- Department of Psychiatry and Human Behavior, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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22
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Choi SS, Han KJ, Lee HK, Han EJ, Suh HW. Possible antinociceptive mechanisms of opioid receptor antagonists in the mouse formalin test. Pharmacol Biochem Behav 2003; 75:447-57. [PMID: 12873637 DOI: 10.1016/s0091-3057(03)00144-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It has been reported that opioid receptor antagonist can induce antinociception in several nociceptive tests. In the intraplantar formalin pain model, however, opioid antagonist-induced antinociception, as well as its underlying mechanism, has not been well characterized. Therefore, in the mouse formalin test, we attempted to characterize the site of action and the possible opioid receptor subtypes. We found that naltrexone (a nonselective opioid antagonist) injected intraperitoneally (i.p., 1-20 mg/kg), intrathecally (i.t., 0.1-10 microg) and intracerebroventricularly (i.c.v., 0.1-10 microg) phase. Administration of beta-funaltrexamine (beta-FNA, 10-40 mg/kg i.p., 1.25-5 microg it or i.c.v.), naltrindole (1-10 mg/kg i.p., 1.25-5 microg it or i.c.v.) and nor-binaltorphimine (nor-BNI, 1-10 mg/kg i.p., 10-40 microg it or i.c.v.), which are selective mu-, delta- and kappa-opioid antagonists, respectively, also produced antinociception during the second phase. Additionally, we examined the involvement of the descending monoaminergic systems in the naltrexone-induced antinociception in the formalin test. Pretreatment with 5,7-dihydroxytryptamine (5,7-DHT, a serotonergic neurotoxin, 20 microg i.t.), but not N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4, a noradrenergic neurotoxin, 20 microg i.t.), reversed the naltrexone-induced antinociception during the second phase. Our results suggest that blockade of supraspinally or spinally located opioid receptors may play roles in the regulation of antinociception during the tonic painful stage. In addition, opioid receptors localized at the neuroterminal of the descending serotonergic, but not noradrenergic, inhibitory system in the spinal cord appear to be involved in opioid antagonist-induced antinociception during the second tonic phase of the formalin test.
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MESH Headings
- 5,7-Dihydroxytryptamine/pharmacology
- Animals
- Behavior, Animal/drug effects
- Benzylamines/pharmacology
- Formaldehyde
- Injections, Intraperitoneal
- Injections, Intraventricular
- Injections, Spinal
- Male
- Mice
- Mice, Inbred ICR
- Naltrexone/analogs & derivatives
- Naltrexone/pharmacology
- Narcotic Antagonists/pharmacology
- Pain Measurement/drug effects
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, mu/antagonists & inhibitors
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Affiliation(s)
- Seong-Soo Choi
- Department of Pharmacology, College of Medicine and Institute of Natural Medicine, Hallym University, 1 Okchundong, Chunchon, Kangwon-Do, 200-702, South Korea
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23
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Anderson WS, Sheth RN, Bencherif B, Frost JJ, Campbell JN. Naloxone increases pain induced by topical capsaicin in healthy human volunteers. Pain 2002; 99:207-16. [PMID: 12237198 DOI: 10.1016/s0304-3959(02)00103-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Opioid receptors occur in locations of strategic importance within the central nervous system for modulation of pain. Is pain reduced by ongoing inhibition mediated by activation of these receptors? Experiments to date in which the opioid-receptor antagonist, naloxone, is administered during a painful event have yielded unclear results. Topically applied capsaicin can be used to induce tonic pain of moderate to severe intensity without tissue injury and is an ideal stimulus for studying acute pain modulation. We therefore conducted a placebo-controlled double-blind crossover study to investigate the effects of naloxone on capsaicin-induced pain (five men, four women, aged 29 +/- 5 years). Capsaicin (10%) was applied topically and subjects rated pain every 2 min. The subjects were told that any drug given to them could increase, decrease, or not change their pain sensation. Pain plateaued after 20 min. At 26 min subjects received either naloxone or placebo in double-blind fashion. At 56 min subjects received the alternative (placebo or naloxone). In a second session the order of presentation was reversed. The naloxone induced a significant increase in pain compared both to baseline (P < 0.01) and placebo (P < 0.01). The peak effect, reached at 12-20 min after naloxone delivery, was 59% greater than placebo. This experiment suggests that acute pain is actively suppressed by endogenous opioid-receptor activation.
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Affiliation(s)
- William S Anderson
- Department of Neurosurgery, School of Medicine, Johns Hopkins University, Meyer 5-109, 600 N Wolfe Street, Baltimore, MD 21287-0817, USA
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Abstract
Under certain experimental and clinical conditions, opioid antagonists have been demonstrated to have analgesic properties. In this open-label, nonrandomized, within-subject comparison, the effect of chronic treatment with the antagonist, naltrexone, on tolerance for experimental pain was evaluated in a small sample of male opioid addicts (N = 10) receiving naltrexone maintenance. Cold-pressor pain tolerance was measured during (> or = 6 weeks) and after discontinuation (> or = 1 week) of naltrexone treatment. Intra-subject comparison revealed that eight of the ten subjects were more pain tolerant (median + 20 sec) while receiving naltrexone. It is suggested that either midbrain opioid system upregulation in the presence of naltrexone or underlying individual differences in pain tolerance in persons with addictive disease provide potential explanations for these findings.
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Affiliation(s)
- P Compton
- UCLA School of Nursing 90095-6918, USA
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25
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Tsuruoka M, Hiruma Y, Willis WD. The subnucleus reticularis dorsalis is involved in antinociception produced by a low dose of naloxone during carrageenan-induced inflammation. Brain Res 1997; 762:264-8. [PMID: 9262188 DOI: 10.1016/s0006-8993(97)00509-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present study was designed to investigate a role of the subnucleus reticularis dorsalis (SRD) in the analgesia produced by a low dose of naloxone during carrageenan-induced inflammation. Male Sprague-Dawley rats were divided into the following two groups: (1) rats with bilateral lesions of the SRD (n = 13) and 2) sham-operated rats (n = 24). In each group, effects of a low dose of naloxone (5 microg/kg, i.p.) on thermal nociception were examined 4 h, 7 and 28 days after the induction of unilateral inflammation. Carrageenan (6 mg in 0.15 ml saline) was injected subcutaneously into the plantar surface of the left hindpaw. The analgesic effect was assessed by prolongation of the paw withdrawal latency (PWL) to heating. Prior to carrageenan injection, a low dose of naloxone did not prolong PWLs in either group. Four hours after carrageenan, a low dose of naloxone produced a prolongation of PWLs in both sham-operated and SRD-lesioned rats. Seven days after carrageenan, naloxone failed to produce analgesia in the SRD-lesioned rats but did produce analgesia in the sham-operated rats. At 28 days, a low dose of naloxone induced hyperalgesia in the inflamed paw of both groups, whereas naloxone was ineffective in the contralateral non-inflamed paw. These results suggest that the SRD plays a role in naloxone-induced analgesia during the subacute phase of inflammation (e.g. 7 days after induction of inflammation).
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Affiliation(s)
- M Tsuruoka
- Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77555-1069, USA. masa@dent showa-u.ac.jp
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Abstract
The role of attentional mechanisms and endogenous opioids in the influence of anxiety on acute pain sensation was investigated. Forty-five spider phobics received mildly painful electrical stimulation. The opioid antagonist naltrexone or placebo was administered between subjects to examine an analgesia due to anxiety-induced endorphinergic activity, while anxiety and focus of attention were manipulated within subjects. In accordance with previous research, pain ratings and skin conductance responses (SCRs) were not influenced by anxiety when focus of attention was controlled for. Attention towards pain led to an increase in subjective pain as opposed to distraction from pain. SCRs, however, were increased in the distraction conditions, probably due to heightened unexpectedness. Further, both high and low anxiety resulted in an analgesia compared to the pretest in the placebo condition, which was reversed by a low dose of naltrexone, but not by a high dose. Apart from possible agonist properties of high doses of naltrexone, this effect suggests an opioid-induced analgesia. It remains to be demonstrated whether this was due to endogenous opioids released during high anxiety.
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Affiliation(s)
- S A Janssen
- Department of Medical Psychology, Limburg University, Maastricht, The Netherlands.
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27
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Crain SM, Shen KF. Ultra-low concentrations of naloxone selectively antagonize excitatory effects of morphine on sensory neurons, thereby increasing its antinociceptive potency and attenuating tolerance/dependence during chronic cotreatment. Proc Natl Acad Sci U S A 1995; 92:10540-4. [PMID: 7479836 PMCID: PMC40647 DOI: 10.1073/pnas.92.23.10540] [Citation(s) in RCA: 164] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Ultra-low picomolar concentrations of the opioid antagonists naloxone (NLX) and naltrexone (NTX) have remarkably potent antagonist actions on excitatory opioid receptor functions in mouse dorsal root ganglion (DRG) neurons, whereas higher nanomolar concentrations antagonize excitatory and inhibitory opioid functions. Pretreatment of naive nociceptive types of DRG neurons with picomolar concentrations of either antagonist blocks excitatory prolongation of the Ca(2+)-dependent component of the action potential duration (APD) elicited by picomolar-nanomolar morphine and unmasks inhibitory APD shortening. The present study provides a cellular mechanism to account for previous reports that low doses of NLX and NTX paradoxically enhance, instead of attenuate, the analgesic effects of morphine and other opioid agonists. Furthermore, chronic cotreatment of DRG neurons with micromolar morphine plus picomolar NLX or NTX prevents the development of (i) tolerance to the inhibitory APD-shortening effects of high concentrations of morphine and (ii) supersensitivity to the excitatory APD-prolonging effects of nanomolar NLX as well as of ultra-low (femtomolar-picomolar) concentrations of morphine and other opioid agonists. These in vitro studies suggested that ultra-low doses of NLX or NTX that selectively block the excitatory effects of morphine may not only enhance the analgesic potency of morphine and other bimodally acting opioid agonists but also markedly attenuate their dependence liability. Subsequent correlative studies have now demonstrated that cotreatment of mice with morphine plus ultra-low-dose NTX does, in fact, enhance the antinociceptive potency of morphine in tail-flick assays and attenuate development of withdrawal symptoms in chronic, as well as acute, physical dependence assays.
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Affiliation(s)
- S M Crain
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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28
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Abbott FV, Franklin KBJ, Westbrook FR. The formalin test: scoring properties of the first and second phases of the pain response in rats. Pain 1995; 60:91-102. [PMID: 7715946 DOI: 10.1016/0304-3959(94)00095-v] [Citation(s) in RCA: 426] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The formalin test is increasingly used as a model of injury-produced pain but there is no generally accepted method of pain rating. To examine the properties of various pain rating methods we established dose-response relations for formalin injected in the plantar surface of one hind paw, and the analgesic effects of morphine and amphetamine using the most frequently reported behavioural measures of pain (favouring, lifting, licking and flinching/shaking of the injured paw) and combinations of these. Licking, elevation and favouring of the injected paw showed a biphasic response at all formalin doses. Flinching varied in form across the time course of formalin, and the biphasic nature of the behaviour was not as apparent. In untreated rats all these behaviours were infrequent. Flinching and favouring were increased after injection of local anaesthetic into the paw but remained negligible relative to the effect of formalin. Grooming other than that directed to the injected paw was elevated in a dose-dependent manner by formalin. Intercorrelations between the behaviours were different for the initial response and the second phase. Correlational analysis indicated that no single behavioural measure was a strong predictor of formalin, morphine and amphetamine dose. A simple sum of time spent licking plus elevating the paw, or the weighted pain score of Dubuisson and Dennis (1977), were superior to any single measure (r ranging from 0.75 to 0.86). Addition of flinching and favouring to the combined pain score using multiple regression did not increase variance explained. Depending on the measure used, a sedative dose of pentobarbital produced apparent analgesia, hyperalgesia or no effect. The interphase depression of pain, as well as the analgesic effects of morphine and amphetamine, were all associated with increased motor activation. Power analysis indicated that using a moderate dose of formalin and a combined pain score gave the greatest power to detect differences in pain. It was also found that pain scores increase with ambient temperature and that rat strains may differ in formalin pain sensitivity.
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Affiliation(s)
- Frances V Abbott
- Department of Psychiatry and School of Nursing, McGill University, Montreal, PQ H3A 1A1, Canada Department of Psychology, McGill University, Montreal, PQ H3A 1A1, Canada School of Psychology, University of New South Wales, Sydney, NSW 2033, Australia
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Influences of age and nociceptive reactivity on the analgesic actions of naltrexone in the rat. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0167-0115(94)90415-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Noble F, Fournié-Zaluski MC, Roques BP. Paradoxical analgesia induced by low doses of naloxone is not potentiated by complete inhibition of enkephalin degradation. Neuropharmacology 1994; 33:135-40. [PMID: 7910383 DOI: 10.1016/0028-3908(94)90108-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The involvement of a presynaptic autoinhibition of endogenous enkephalin release has been suggested as a possible explanation for the paradoxical analgesia induced by low doses of naloxone. This hypothesis was investigated by using the systemically active mixed inhibitor of enkephalin degrading enzymes, RB 101. As already described, in both hot plate (55 +/- 0.5 degrees C) and acetic acid (0.6%) abdominal constriction tests in mice, subcutaneous administration of naloxone produced biphasic effects, with antinociceptive responses at very low doses (microgram range) and hyperalgesia at higher dose (mg range). However at concentrations producing an extracellular increase in enkephalin levels and subsequent analgesia, the mixed inhibitor prodrug of the enkephalin-metabolizing enzymes RB 101 (20 or 100 mg/kg i.v. and 5 or 10 mg/kg i.v., in the hot plate test and in the abdominal constriction test, respectively) did not potentiate the paradoxical analgesia induced by naloxone. These results are inconsistent with a negative autoregulation of endogenous enkephalin release and could suggest the involvement of the diffuse noxious inhibitory controls (DNIC). Indeed, the finding that low doses of RB 101 (1 mg/kg i.v. in the hot plate test, and 250 micrograms/kg i.v. in the abdominal constriction test) were able to induce hyperalgesic responses could indicate that the DNIC are tonically activated by endogenous enkephalins accounting for the antinociceptive responses elicited by low doses of naloxone.
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Affiliation(s)
- F Noble
- Département de Pharmacochimie Moléculaire et Structurale, U266 INSERM-URA D1500 CNRS, Université René Descartes, Paris, France
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Hamann SR, Martin WR. Hyperalgesic and analgesic actions of morphine, U50-488, naltrexone, and (-)-lobeline in the rat brainstem. Pharmacol Biochem Behav 1994; 47:197-201. [PMID: 8115422 DOI: 10.1016/0091-3057(94)90131-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Morphine, U50-488, and (-)-lobeline produced dose-related shortening of a low-intensity thermally evoked tail avoidance response (LITETAR) (e.g., hyperalgesia) when microinjected into the dorsal posterior mesencephalic tegmentum (DPMT) of conscious rats. The hyperalgesic potency of (-)-lobeline was greater than either morphine or U50-488. With higher doses, morphine's hyperalgesic actions diminished and prolongation of the LITETAR (e.g., analgesia) was observed. Naltrexone produced analgesia in the DPMT that diminished with increasing dose. The hyperalgesic actions of morphine, U50-488, and (-)-lobeline further suggest the presence of kappaergic opioid and nicotinic mechanisms in the DPMT of rats. The hyperalgesic actions of U50-488, a highly specific opioid kappa-receptor agonist, strongly suggest the presence of a kappa-opioidergic hyperalgesic mechanism in the DPMT.
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Affiliation(s)
- S R Hamann
- Department of Anesthesiology, College of Medicine, University of Kentucky, Lexington 40536-0216
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Kalyuzhnyi LV, Kozlov AY, Litvinova SV. Enkephalinase mechanisms of resistance and tolerance to the analgesic action of morphine in rats. II. Differential effects of naloxone in morphine-sensitive, morphine-resistant, and morphine-tolerant rats. Bull Exp Biol Med 1993. [DOI: 10.1007/bf00786143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Mokha SS. Differential influence of naloxone on the responses of nociceptive neurons in the superficial versus the deeper dorsal horn of the medulla in the rat. Pain 1992; 49:405-413. [PMID: 1408306 DOI: 10.1016/0304-3959(92)90248-a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Naloxone (200 micrograms/kg, i.v.) reduced the noxious thermal stimuli-evoked responses of 16/25 nociceptive neurons in the superficial laminae whereas it enhanced the responses of 6/10 nociceptive neurons in the deeper dorsal horn. However, a different picture emerged when selectivity of neuronal responsivity (nocireceptive or multireceptive) was considered. In the superficial dorsal horn, naloxone reduced the responses of the majority of (15/18) selectively nocireceptive neurons. The reduction in responses became apparent within 60 sec following naloxone administration and returned to control level within 48 min. In contrast, the responses of the majority of multireceptive neurons in the superficial (6/7), or the deeper (6/10) dorsal horn, were enhanced. The excitatory action in the superficial dorsal horn persisted for only 6-15 min, whereas it persisted for 40-70 min in the deeper dorsal horn. The firing of the majority of cold-receptive neurons (6/8) in the superficial dorsal horn was not altered. These effects were stereoselective since (+)-naloxone, the inactive isomer of naloxone, did not affect the responses of 14/16 nociceptive neurons. It is concluded that naloxone differentially, and selectively, affects the firing of nociceptive neurons in the superficial versus the deeper dorsal horn, and the firing of selectively nocireceptive versus multireceptive neurons. The relevance of these findings to the behavioral effects of naloxone, hyperalgesia and analgesia, is discussed.
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Affiliation(s)
- S S Mokha
- Department of Physiology, Meharry Medical College, Nashville, TN 37208 USA Division of Neurophysiogy and Neuropharmacology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA UK
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Willer JC, Le Bars D, De Broucker T. Diffuse noxious inhibitory controls in man: involvement of an opioidergic link. Eur J Pharmacol 1990; 182:347-55. [PMID: 2168836 DOI: 10.1016/0014-2999(90)90293-f] [Citation(s) in RCA: 155] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In man, heterotopic painful thermal conditioning stimuli induce parallel decreases in the spinal nociceptive flexion (RIII) reflex and the concurrent sensation of pain elicited by electrical stimulation of the sural nerve at the ankle. Such phenomena may be related to the diffuse noxious inhibitory controls (DNIC) which were initially described in the rat and subsequently documented in humans. In nine subjects in the present study, a 2-min application of a moderately noxious temperature (46 degrees C) to the contralateral hand strongly depressed the RIII reflex elicited in the biceps femoris muscle by electrical stimulation of the sural nerve at 1.2 times the reflex threshold. These depressive effects were maximal during the 2nd min of the conditioning period, showing an almost complete inhibition of the RIII reflex which gradually recovered its baseline value 6-9 min after the end of the conditioning period. Using a double-blind, cross-over design, it was found that these inhibitory effects were completely blocked 5 min after naloxone hydrochloride administration (0.4 mg i.v.) whereas the administration of saline was totally ineffective. The lifting of the inhibitions was compatible with the short duration of the pharmacological effects of naloxone in that the inhibitions were observed again 50 min after the naloxone injection. During all the experimental sessions, heart and respiratory rates remained stable at their control levels. It is concluded that the loop subserving DNIC which ascends from--and redescends to--the spinal cord involves an opioidergic link in man as in experimental animals. Possible implications for hypoalgesia based on the principles of counter-irritation or elicited by naloxone are discussed.
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Affiliation(s)
- J C Willer
- Laboratoire de Neurophysiologie, Faculté de Médicine Pitié-Salpêtrière, Paris, France
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Lipman JJ, Miller BE, Mays KS, Miller MN, North WC, Byrne WL. Peak B endorphin concentration in cerebrospinal fluid: reduced in chronic pain patients and increased during the placebo response. Psychopharmacology (Berl) 1990; 102:112-6. [PMID: 2144051 DOI: 10.1007/bf02245754] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The level of an endogenous opioid (peak B endorphin) was measured in chromatographically fractionated cerebrospinal fluid (CSF) sampled from two groups of chronic pain patients before and after intrathecal saline (placebo) injection. As assessed by a verbal rating scale, one group reported no change in their level of pain (non-responders, NR; n = 6) while the other group reported complete or greater than 50% pain relief (placebo responders, PR; n = 14). We find, as has been reported previously, that initial peak B levels were lower (by 50%) in these chronic pain patients' CSF than in CSF from pain-free (PF) normal controls (P less than 0.001, t-test). Peak B levels measured from CSF of the NR group undergoing this procedure did not change (P greater than 0.4, paired t-test). In contrast, a significant 2.3-fold increase was measured in the CSF peak B level of the PR group (P less than 0.05, paired t-test). This is the first direct evidence that a CSF opioid is correlated with placebo pain relief in chronic pain patients. Peak B is a potent analgesic substance when administered by the intracerebroventricular route in mice and its level is related to the patients' pain status in a presumably causal manner.
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Affiliation(s)
- J J Lipman
- Department of Biochemistry, University of Tennessee Center for the Health Sciences, Memphis 38163
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Porchet HC, Piletta P, Dayer P. Objective assessment of clonidine analgesia in man and influence of naloxone. Life Sci 1990; 46:991-8. [PMID: 2182959 DOI: 10.1016/0024-3205(90)90022-j] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Experimental data indicate that clonidine can induce marked analgesia. We characterized this effect in healthy volunteers and investigated possible links with the opioid peptide system by means of naloxone antagonism. According to a cross-over, double-blind, placebo-controlled design, 10 subjects received oral and i.v. placebo or clonidine (0.2 mg p.o.) or clonidine and naloxone (2.8 mg i.v. in 5 h). Analgesia was assessed by measurement of the subjective pain threshold (visual analog scale) and the objective nociceptive flexion reflex (R III) threshold after transcutaneous electrical stimulations. A correlation was observed between subjective and objective thresholds (r: 0.78). Oral clonidine alone or with naloxone increased subjective and objective pain thresholds for at least 4 hours (p less than 0.01, ANOVA). Naloxone tended to reinforce clonidine analgesia. Only moderate and well tolerated side-effects were observed.
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Affiliation(s)
- H C Porchet
- Department of Medicine, University Hospital, Geneva, Switzerland
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Bengtsson M, Bengtsson A, Jorfeldt L. Diagnostic epidural opioid blockade in primary fibromyalgia at rest and during exercise. Pain 1989; 39:171-180. [PMID: 2594395 DOI: 10.1016/0304-3959(89)90004-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Nine patients with primary fibromyalgia participated. The patients were studied prior to, during and immediately after 4 identical periods of exercise (bicycle ergometer) each performed 30 min after injection with saline, repeated saline, an opioid and naloxone. All substances were given epidurally, except for naloxone which was given intravenously. Finally, with the patients resting in bed, lignocaine was injected epidurally. Physiological variables, general exertion, dyspnoea, lower extremity exhaustion, pain and tender points in the lower half of the body were examined. Resting pain and tender points diminished significantly after the opioid injection. Lignocaine completely abolished resting pain and tender points. Lower extremity exhaustion was reduced by the opioid. General exertion and dyspnoea were unaffected by the opioid. In conclusion the results support the hypothesis that the pain in fibromyalgia is of peripheral nociceptive or spinal origin. We raise the hypothesis that the fatigability is, at least partly, due to inhibition because of pain.
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Affiliation(s)
- Mats Bengtsson
- Department of Anaesthesiology,University Hospital, S-581 85 LinköpingSweden Department of Internal Medicine, Division of Rheumatology,University Hospital, S-581 85 LinköpingSweden Department of Clinical Physiology, University Hospital, S-581 85 LinköpingSweden
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Kayser V, Besson JM, Guilbaud G. Paradoxical effects of low doses of naloxone in experimental models of inflammatory pain. PROGRESS IN BRAIN RESEARCH 1988; 77:301-12. [PMID: 3217532 DOI: 10.1016/s0079-6123(08)62796-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Abstract
The effects of systemic naloxone on pain behaviour in rats were examined in modified formalin test. Dilute formalin was subcutaneously injected in the plantar surface of the hindpaw, after which pain was rated according to behavioural criteria. Fifteen minutes after formalin injection, naloxone in various doses (10 micrograms/kg, 100 micrograms/kg, 300 micrograms/kg, 600 micrograms/kg, 800 micrograms/kg, 2000 micrograms/kg) or saline was intraperitoneally injected. Pain behaviour in naloxone injected and saline injected rats was not different. The findings are discussed in relation to previous reports about naloxone effects on different types of pain.
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Affiliation(s)
- L Kocher
- Laboratoire de Physiologie, Université Claude Bernard, Faculté de Médecine Lyon-Sud, Oullins, France
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