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Schwarting RKW, Wöhr M, Engler H, Sungur AÖ, Schedlowski M. Behaviorally conditioned effects of psychoactive drugs in experimental animals: What we have learned from nearly a century of research and what remains to be learned. Neurosci Biobehav Rev 2024; 162:105721. [PMID: 38754716 DOI: 10.1016/j.neubiorev.2024.105721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Revised: 04/26/2024] [Accepted: 05/10/2024] [Indexed: 05/18/2024]
Abstract
Continuous treatment with drugs is a crucial requirement for managing various clinical conditions, including chronic pain and neuropsychiatric disorders such as depression or schizophrenia. Associative learning processes, i.e. Pavlovian conditioning, can play an important role for the effects of drugs and could open new avenues for optimizing patient treatment. In this narrative literature review, we summarize available data in experimental animals regarding the behaviorally conditioned effects of psychostimulants such as d-amphetamine and cocaine, the dopamine receptor agonist apomorphine, the dopamine receptor antagonist haloperidol, morphine and antidepressant drugs. In each section, the drug under discussion is briefly introduced, followed by a detailed examination of conditioning features, including doses and dosing regimens, characteristics of the conditioning process such as test environments or specific conditioned stimuli, testing and conditioned response characteristics, possible extinction or reconditioning or reversal training, neural mechanisms, and finally, the potential clinical relevance of the research area related to the drug. We focus on key outcomes, delve into methodical issues, identify gaps in current knowledge, and suggest future research directions.
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Affiliation(s)
- Rainer K W Schwarting
- Philipps-University of Marburg, Faculty of Psychology, Experimental and Biological Psychology, Behavioral Neuroscience, Marburg D-35032, Germany; Center for Mind, Brain and Behavior, Marburg D-35032, Germany
| | - Markus Wöhr
- Philipps-University of Marburg, Faculty of Psychology, Experimental and Biological Psychology, Behavioral Neuroscience, Marburg D-35032, Germany; Center for Mind, Brain and Behavior, Marburg D-35032, Germany; KU Leuven, Faculty of Psychology and Educational Sciences, Research Unit Brain and Cognition, Laboratory of Biological Psychology, Social and Affective Neuroscience Research Group, Leuven B-3000, Belgium; KU Leuven, Leuven Brain Institute, Leuven B-3000, Belgium
| | - Harald Engler
- Institute of Medical Psychology and Behavioral Immunobiology, Center for Translational Neuro-, and Behavioral Sciences, University Hospital Essen, University of Duisburg-Essen, Essen D-45147, Germany
| | - A Özge Sungur
- Philipps-University of Marburg, Faculty of Psychology, Experimental and Biological Psychology, Behavioral Neuroscience, Marburg D-35032, Germany; Center for Mind, Brain and Behavior, Marburg D-35032, Germany; KU Leuven, Faculty of Psychology and Educational Sciences, Research Unit Brain and Cognition, Laboratory of Biological Psychology, Social and Affective Neuroscience Research Group, Leuven B-3000, Belgium; KU Leuven, Leuven Brain Institute, Leuven B-3000, Belgium
| | - Manfred Schedlowski
- Institute of Medical Psychology and Behavioral Immunobiology, Center for Translational Neuro-, and Behavioral Sciences, University Hospital Essen, University of Duisburg-Essen, Essen D-45147, Germany; Department of Clinical Neuroscience, Osher Center for Integrative Medicine, Karolinska Institutet, Stockholm 171 77, Sweden
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Totsch SK, Sorge RE. A novel investigation of placebo analgesia through social communication in mice. Behav Brain Res 2024; 459:114773. [PMID: 38000532 DOI: 10.1016/j.bbr.2023.114773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 11/08/2023] [Accepted: 11/20/2023] [Indexed: 11/26/2023]
Abstract
BACKGROUND AND AIMS In rodents, placebo analgesia is often investigated through direct conditioning of stimuli, but humans can experience placebo analgesia through expectation without experience. In this study, we sought to determine whether placebo analgesia could be elicited through social communication. METHODS Male and female mice were housed in pairs (designated "Active" and "Bystander") and tested for thermal thresholds on a hot plate (53 °C). Food restriction (1 hr/day) was implemented. The Active mouse was taken to a new cage with food dusted with cocoa (COC) or cinnamon (CINN). The Bystander mice were given regular chow in the home cage. After feeding, the Active mice were given morphine (5 mg/kg, SC) or saline and tested on the hot plate. After 5 pairings of a flavor and treatment (counterbalanced), Active mice were tested following access to a flavored food. Bystander mice were given their first direct exposure to a flavored food and tested on the hot plate. The protocol was repeated with naloxone (10 mg/kg, IP) administered prior to testing. Finally, mice were tested in a two-choice test with both flavored foods available. RESULTS Active mice showed a conditioned analgesic response to the morphine-paired flavor that was reduced by naloxone. Bystander mice showed a placebo analgesic response to their cagemate's morphine-paired flavor that was not significantly impacted by naloxone. Bystander mice spent more time in the chamber associated with their cagemate's morphine-paired flavor. CONCLUSIONS To our knowledge, this is the first investigation of placebo analgesia without direct conditioning, instead relying on social communication between mice. The lack of effect with naloxone pretreatment suggests an opioid-independent effect in the Bystander mice. Placebo analgesia in mice may be possible without direct conditioning to better model the effect of expectation of a novel analgesic in humans.
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Affiliation(s)
- Stacie K Totsch
- Department of Psychology, University of Alabama at Birmingham, United States
| | - Robert E Sorge
- Department of Psychology, University of Alabama at Birmingham, United States.
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Kwon AH, Colloca L, Mackey SC. Blinded Pain Cocktails: A Reliable and Safe Opioid Weaning Method. Anesthesiol Clin 2023; 41:371-381. [PMID: 37245948 DOI: 10.1016/j.anclin.2023.03.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Weaning opioids in patients with noncancerous chronic pain often poses a challenge when psychosocial factors complicate the patient's chronic pain syndrome and opioid use. A blinded pain cocktail protocol used to wean opioid therapy has been described since the 1970s. At the Stanford Comprehensive Interdisciplinary Pain Program, a blinded pain cocktail remains a reliably effective medication-behavioral intervention. This review (1) outlines psychosocial factors that may complicate opioid weaning, (2) describes clinical goals and how to use blinded pain cocktails in opioid tapering, and (3) summarizes the mechanism of dose-extending placebos and ethical justification of its use in clinical practice.
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Affiliation(s)
- Albert Hyukjae Kwon
- Stanford University School of Medicine, 430 Broadway Street, Pavilion C, 3rd Floor, Redwood City, CA 94063, USA.
| | - Luana Colloca
- Pain and Translational Symptom Science, Placebo Beyond Opinions Center, School of Nursing, University of Maryland, Baltimore, 655 West Lombard Street, Room 729A, Baltimore, MD 21201, USA
| | - Sean C Mackey
- Stanford University School of Medicine, 1070 Arastradero Road, Suite 200, Palo Alto, CA 94304, USA
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Abdus-Saboor I, Luo W. Measuring Mouse Somatosensory Reflexive Behaviors with High-speed Videography, Statistical Modeling, and Machine Learning. NEUROMETHODS 2022; 178:441-456. [PMID: 35783537 PMCID: PMC9249079 DOI: 10.1007/978-1-0716-2039-7_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Objectively measuring and interpreting an animal's sensory experience remains a challenging task. This is particularly true when using preclinical rodent models to study pain mechanisms and screen for potential new pain treatment reagents. How to determine their pain states in a precise and unbiased manner is a hurdle that the field will need to overcome. Here, we describe our efforts to measure mouse somatosensory reflexive behaviors with greatly improved precision by high-speed video imaging. We describe how coupling sub-second ethograms of reflexive behaviors with a statistical reduction method and supervised machine learning can be used to create a more objective quantitative mouse "pain scale." Our goal is to provide the readers with a protocol of how to integrate some of the new tools described here with currently used mechanical somatosensory assays, while discussing the advantages and limitations of this new approach.
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Affiliation(s)
- Ishmail Abdus-Saboor
- Department of Biology, University of Pennsylvania, 3740 Hamilton Walk, Philadelphia, PA, 19104, USA
| | - Wenqin Luo
- Department of Neuroscience, University of Pennsylvania, 3610 Hamilton Walk, Philadelphia, PA, 19104, USA
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Caudle RM, Neubert JK. Effects of Oxaliplatin on Facial Sensitivity to Cool Temperatures and TRPM8 Expressing Trigeminal Ganglion Neurons in Mice. FRONTIERS IN PAIN RESEARCH 2022; 3:868547. [PMID: 35634452 PMCID: PMC9130462 DOI: 10.3389/fpain.2022.868547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 04/18/2022] [Indexed: 12/04/2022] Open
Abstract
The chemotherapeutic agent oxaliplatin is commonly used to treat colorectal cancer. Although effective as a chemotherapeutic, it frequently produces painful peripheral neuropathies. These neuropathies can be divided into an acute sensitivity to cool temperatures in the mouth and face, and chronic neuropathic pain in the limbs and possible numbness. The chronic neuropathy also includes sensitivity to cool temperatures. Neurons that detect cool temperatures are reported to utilize Transient Receptor Potential Cation Channel, Subfamily M, Member 8 (TRPM8). Therefore, we investigated the effects of oxaliplatin on facial nociception to cool temperatures (18°C) in mice and on TRPM8 expressing trigeminal ganglion (TRG) neurons. Paclitaxel, a chemotherapeutic that is used to treat breast cancer, was included for comparison because it produces neuropathies, but acute cool temperature sensitivity in the oral cavity or face is not typically reported. Behavioral testing of facial sensitivity to 18°C indicated no hypersensitivity either acutely or chronically following either chemotherapeutic agent. However, whole cell voltage clamp experiments in TRPM8 expressing TRG neurons indicated that both oxaliplatin and paclitaxel increased Hyperpolarization-Activated Cyclic Nucleotide-Gated channel (HCN), voltage gated sodium channel (Nav), and menthol evoked TRPM8 currents. Voltage gated potassium channel (Kv) currents were not altered. Histological examination of TRPM8 fibers in the skin of the whisker pads demonstrated that the TRPM8 expressing axons and possible Merkel cell-neurite complexes were damaged by oxaliplatin. These findings indicate that oxaliplatin induces a rapid degeneration of TRG neuron axons that express TRPM8, which prevents evoked activation of the sensitized neurons and likely leads to reduced sensitivity to touch and cool temperatures. The changes in HCN, Nav, and TRPM8 currents suggest that spontaneous firing of action potentials may be increased in the deafferented neurons within the ganglion, possibly producing spontaneously induced cooling or nociceptive sensations.
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Affiliation(s)
- Robert M. Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, United States
| | - John K. Neubert
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
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Benedetti F, Frisaldi E, Shaibani A. Thirty Years of Neuroscientific Investigation of Placebo and Nocebo: The Interesting, the Good, and the Bad. Annu Rev Pharmacol Toxicol 2021; 62:323-340. [PMID: 34460317 DOI: 10.1146/annurev-pharmtox-052120-104536] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Over the past 30 years there has been a surge of research on the placebo effect using a neuroscientific approach. The interesting aspects of this effort are related to the identification of several biological mechanisms of both the placebo and nocebo effects, the latter of which is defined as a negative placebo effect. Some important translational implications have emerged both in the setting of clinical trials and in routine medical practice. One of the principal contributions of neuroscience has been to draw the attention of the scientific and medical communities to the important role of psychobiological factors in therapeutic outcomes, be they drug related or not. Indeed, many biological mechanisms triggered by placebos and nocebos resemble those modulated by drugs, suggesting a possible interaction between psychological factors and drug action. Unfortunately, this new knowledge regarding placebos has the potential of being dangerously exploited by pseudoscience. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Fabrizio Benedetti
- Department of Neuroscience, University of Turin Medical School, Turin I-10125, Italy; .,Medicine and Physiology of Hypoxia, Plateau Rosà CH-3920, Switzerland
| | - Elisa Frisaldi
- Department of Neuroscience, University of Turin Medical School, Turin I-10125, Italy;
| | - Aziz Shaibani
- Nerve and Muscle Center of Texas and Baylor College of Medicine, Houston, Texas 77030, USA
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Cho C, Deol HK, Martin LJ. Bridging the Translational Divide in Pain Research: Biological, Psychological and Social Considerations. Front Pharmacol 2021; 12:603186. [PMID: 33935700 PMCID: PMC8082136 DOI: 10.3389/fphar.2021.603186] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 02/22/2021] [Indexed: 12/29/2022] Open
Abstract
A gap exists between translating basic science research into effective pain therapies in humans. While preclinical pain research has primarily used animal models to understand biological processes, a lesser focus has been toward using animal models to fully consider other components of the pain experience, such as psychological and social influences. Herein, we provide an overview of translational studies within pain research by breaking them down into purely biological, psychological and social influences using a framework derived from the biopsychosocial model. We draw from a wide landscape of studies to illustrate that the pain experience is highly intricate, and every attempt must be made to address its multiple components and interactors to aid in fully understanding its complexity. We highlight our work where we have developed animal models to assess the cognitive and social effects on pain modulation while conducting parallel experiments in people that provide proof-of-importance for human pain modulation. In some instances, human pain research has sparked the development of novel animal models, with these animal models used to better understand the complexity of phenomena considered to be uniquely human such as placebo responses and empathy.
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Affiliation(s)
- Chulmin Cho
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Harashdeep K Deol
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Loren J Martin
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
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8
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Mouraux A, Bannister K, Becker S, Finn DP, Pickering G, Pogatzki-Zahn E, Graven-Nielsen T. Challenges and opportunities in translational pain research - An opinion paper of the working group on translational pain research of the European pain federation (EFIC). Eur J Pain 2021; 25:731-756. [PMID: 33625769 PMCID: PMC9290702 DOI: 10.1002/ejp.1730] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
For decades, basic research on the underlying mechanisms of nociception has held promise to translate into efficacious treatments for patients with pain. Despite great improvement in the understanding of pain physiology and pathophysiology, translation to novel, effective treatments for acute and chronic pain has however been limited, and they remain an unmet medical need. In this opinion paper bringing together pain researchers from very different disciplines, the opportunities and challenges of translational pain research are discussed. The many factors that may prevent the successful translation of bench observations into useful and effective clinical applications are reviewed, including interspecies differences, limited validity of currently available preclinical disease models of pain, and limitations of currently used methods to assess nociception and pain in non-human and human models of pain. Many paths are explored to address these issues, including the backward translation of observations made in patients and human volunteers into new disease models that are more clinically relevant, improved generalization by taking into account age and sex differences, and the integration of psychobiology into translational pain research. Finally, it is argued that preclinical and clinical stages of developing new treatments for pain can be improved by better preclinical models of pathological pain conditions alongside revised methods to assess treatment-induced effects on nociception in human and non-human animals. Significance: For decades, basic research of the underlying mechanisms of nociception has held promise to translate into efficacious treatments for patients with pain. Despite great improvement in the understanding of pain physiology and pathophysiology, translation to novel, effective treatments for acute and chronic pain has however been limited, and they remain an unmet medical need.
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Affiliation(s)
- André Mouraux
- Institute of Neuroscience (IONS), UCLouvain, Brussels, Belgium
| | - Kirsty Bannister
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Susanne Becker
- Department of Cognitive and Clinical Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.,Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - David P Finn
- Pharmacology and Therapeutics, Centre for Pain Research, School of Medicine, National University of Ireland Galway, Galway, Ireland
| | - Gisèle Pickering
- Department of Clinical Pharmacology, Inserm CIC 1405, University Hospital, CHU Clermont-Ferrand, France.,Fundamental and Clinical Pharmacology of Pain, University Clermont Auvergne, Clermont-Ferrand, France
| | - Esther Pogatzki-Zahn
- Department of Anesthesiology, Critical Care Medicine and Pain Therapy, University Hospital Muenster, Muenster, Germany
| | - Thomas Graven-Nielsen
- Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark
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Morphine-Conditioned Placebo Analgesia in Female and Male Rats with Chronic Neuropathic Pain: c-Fos Expression in the Rostral Ventromedial Medulla. Neuroscience 2020; 457:51-73. [PMID: 33285237 DOI: 10.1016/j.neuroscience.2020.11.038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/19/2020] [Accepted: 11/23/2020] [Indexed: 12/17/2022]
Abstract
Placebo analgesia has great potential to overcome the inadequacies of current drug therapies to treat conditions of chronic pain. The rostral ventromedial medulla (RVM) has been implicated as a critical relay in the antinociceptive pathway underpinning placebo analgesia in humans. We developed a model of opiate-conditioned placebo analgesia in rats with neuropathic injury to identify medullary nuclei active during placebo analgesia. Using female and male rats the degree of thermal allodynia was first determined following nerve injury, and a pharmacological conditioning procedure, pairing contextual cues with the experience of morphine-induced analgesia, was used to elicit placebo analgesic reactions. This protocol revealed clear subpopulations of placebo reactors (36% of males, 25% of females) and non-reactors in proportions similar to those reported in human studies. We detected injury-specific c-Fos expression in the gracile nucleus and morphine-specific c-Fos expression in the serotonergic midline raphe nuclei and the caudal nuclei of the solitary tract. However, c-Fos expression did not differ between placebo reactors and non-reactors in either serotonergic or non-serotonergic neurons of the RVM. Despite a subpopulation of rats demonstrating placebo reactions, we found no evidence for enhanced activity in the nuclei from which the classical RVM → spinal cord descending analgesic pathways emerge.
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10
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Caudle RM, Caudle SL, Flenor ND, Rohrs EL, Neubert JK. Pharmacological Characterization of Orofacial Nociception in Female Rats Following Nitroglycerin Administration. Front Pharmacol 2020; 11:527495. [PMID: 33343340 PMCID: PMC7744726 DOI: 10.3389/fphar.2020.527495] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 10/19/2020] [Indexed: 11/13/2022] Open
Abstract
Rodent models of human disease can be valuable for understanding the mechanisms of a disease and for identifying novel therapies. However, it is critical that these models be vetted prior to committing resources to developing novel therapeutics. Failure to confirm the model can lead to significant losses in time and resources. One model used for migraine headache is to administer nitroglycerin to rodents. Nitroglycerin is known to produce migraine-like pain in humans and is presumed to do the same in rodents. It is not known, however, if the mechanism for nitroglycerin headaches involves the same pathological processes as migraine. In the absence of known mechanisms, it becomes imperative that the model not only translates into successful clinical trials but also successfully reverse translates by demonstrating efficacy of current therapeutics. In this study female rats were given nitroglycerin and nociception was evaluated in OPADs. Estrous was not monitored. Based on the ED50 of nitroglycerin a dose of 10 mg/kg was used for experiments. Sumatriptan, caffeine, buprenorphine and morphine were administered to evaluate the reverse translatability of the model. We found that nitroglycerin did not produce mechanical allodynia in the face of the rats, which is reported to be a consequence of migraine in humans. Nitroglycerin reduced the animals’ participation in the assay. The reduced activity was verified using an assay to measure exploratory behavior. Furthermore, the effects of nitroglycerin were not reversed or prevented by agents that are effective acute therapies for migraine. Two interesting findings from this study, however, were that morphine and nitroglycerin interact to increase the rats’ tolerance of mechanical stimuli on their faces, and they work in concert to slow down the central motor pattern generator for licking on the reward bottle. These interactions suggest that nitroglycerin generated nitric oxide and mu opioid receptors interact with the same neuronal circuits in an additive manner. The interaction of nitroglycerin and morphine on sensory and motor circuits deserves additional examination. In conclusion, based on the results of this study the use of nitroglycerin at these doses in naïve female rats is not recommended as a model for migraine headaches.
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Affiliation(s)
- Robert M Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, United States
| | - Stephanie L Caudle
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
| | - Natalie D Flenor
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
| | - Eric L Rohrs
- Velocity Laboratories, LLC, Alachua, FL, United States
| | - John K Neubert
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
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Maity S, Priyadharshini V, Basavaraju S. A comparative evaluation of propolis and light-cured ormocer-based desensitizer in reducing dentin hypersensitivity. J Indian Soc Periodontol 2020; 24:441-446. [PMID: 33144772 PMCID: PMC7592609 DOI: 10.4103/jisp.jisp_500_19] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 01/30/2020] [Accepted: 02/06/2020] [Indexed: 11/04/2022] Open
Abstract
Objectives The purpose of the study was to evaluate and compare the clinical efficacy and the durability of propolis and Light-cured ormocer-based desensitizer (Admira Protect, Voco: Cuxhaven Germany) in the treatment of dentin hypersensitivity (DH). Materials and Methods The study was conducted over a period of 2 months on 13 patients with 72 hypersensitive teeth, randomly allocated into three treatment groups: Group A: Treated with Propolis, Group B: Admira protect (Voco: Cuxhaven Germany), and Group C: Sterile water (Placebo control). Baseline sensitivity was recorded by the operator using tactile and evaporative stimuli. Visual analog scale (VAS) was used to record the degree of sensitivity perceived by the patients. All the groups received applications of allotted materials on day 1, 7, 14, and 21. After each applications VAS scoring was recorded. On day 30 and 60, only pain evaluation was done to determine the durability of each test materials. Statistical Analysis One-way ANOVA, repeated measure ANOVA and post hoc test was done for multiple comparison. Results All the groups showed significant results in reducing DH. Among Groups A and B, Group B showed immediate postoperative result at the end of the 1st week. Conclusion Both the test materials were effective in reducing DH but Admira protect was found to be more efficient in reducing pain with longer duration of action (CTRI regd no: CTRI/2017/12/010755).
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Affiliation(s)
- Snigdha Maity
- Department of Periodontology, JSS Dental College and Hospital, Mysuru, Karnataka, India
| | - Vidya Priyadharshini
- Department of Periodontology, JSS Dental College and Hospital, Mysuru, Karnataka, India
| | - Suman Basavaraju
- Department of Periodontology, JSS Dental College and Hospital, Mysuru, Karnataka, India
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Yin XS, Yang JY, Cao S, Wang Y. Failure of Placebo Analgesia Model in Rats with Inflammatory Pain. Neurosci Bull 2019; 36:121-133. [PMID: 31435837 DOI: 10.1007/s12264-019-00420-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 05/21/2019] [Indexed: 12/15/2022] Open
Abstract
With the shifting role of placebos, there is a need to develop animal models of placebo analgesia and elucidate the mechanisms underlying the effect. In the present study, male Sprague-Dawley rats with chronic inflammatory pain caused by complete Freund's adjuvant (CFA) underwent a series of conditioning procedures, in which morphine was associated with different cues, but they failed to induce placebo analgesia. Then, conditioning with the conditioned place preference apparatus successfully induced analgesic expectancy and placebo analgesia in naïve rats but only induced analgesic expectancy and no analgesic effect in CFA rats. Subsequently, we found enhanced c-fos expression in the nucleus accumbens and reduced expression in the anterior cingulate cortex in naïve rats while c-fos expression in the anterior cingulate cortex in CFA rats was not altered. In summary, the behavioral conditioning model demonstrated the difficulty of establishing a placebo analgesia model in rats with a pathological condition.
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Affiliation(s)
- Xiang-Sha Yin
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Key Laboratory for Neuroscience, Ministry of Education of China, and National Health Commission, State key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, 100083, China
| | - Jin-Yu Yang
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Key Laboratory for Neuroscience, Ministry of Education of China, and National Health Commission, State key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, 100083, China
| | - Shuai Cao
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Key Laboratory for Neuroscience, Ministry of Education of China, and National Health Commission, State key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, 100083, China
| | - Yun Wang
- Department of Neurobiology, School of Basic Medical Sciences and Neuroscience Research Institute, Key Laboratory for Neuroscience, Ministry of Education of China, and National Health Commission, State key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, 100083, China.
- PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China.
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Puviani L, Rama S. Understanding and exploiting prediction errors minimization within the brain in pharmacological treatments. Behav Brain Res 2018; 359:223-233. [PMID: 30395877 DOI: 10.1016/j.bbr.2018.10.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 10/14/2018] [Accepted: 10/15/2018] [Indexed: 11/26/2022]
Abstract
The human brain can be conceptualized as an inference machine that actively predicts and explains its sensations and perceptions: it makes predictions through a probabilistic model. Such a model is continuously and implicitly updated by the computation and minimization of weighted prediction errors, as shown by numerous studies and experimental results. Nevertheless, such an algorithmic functioning of the brain has not been exploited in the neuropharmacological practice. In this manuscript, we show by theoretical analysis and model fitting of previously published data in two different contexts, how it is possible to increase the effectiveness of neuropharmacological and immunosuppressive drugs, through the modulation of the weighted prediction errors. Moreover, on the basis of the proposed model, we derive an optimized drug administration schedule able to increase the drug effectiveness of one order of magnitude, in psoriasis treatment. We make important testable predictions, evidencing the impact and the potential benefit of prediction errors modulation within the brain, in the pharmacotherapeutic practice. Finally, our results lead to a novel formal theory of implicit learning, and shed lights on the actual roles of classical conditioning and UCS revaluation in behavioral and pharmacological conditioning experiments. The potential practical implications of our results are many: the reduction of drugs side effects; the maximization of the therapeutic outcome; a more effective treatment for chronic pain, certain neuropsychiatric diseases, autoimmune diseases and allergic diseases.
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Affiliation(s)
- Luca Puviani
- University of Modena and Reggio Emilia, via Vivarelli 10, Modena, Italy.
| | - Sidita Rama
- Local Medical Unit, Via San Giovanni del Cantone, 23, Modena, Italy
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14
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A Context-Based Analgesia Model in Rats: Involvement of Prefrontal Cortex. Neurosci Bull 2018; 34:1047-1057. [PMID: 30178433 PMCID: PMC6246847 DOI: 10.1007/s12264-018-0279-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 05/03/2018] [Indexed: 01/01/2023] Open
Abstract
Cognition and pain share common neural substrates and interact reciprocally: chronic pain compromises cognitive performance, whereas cognitive processes modulate pain perception. In the present study, we established a non-drug-dependent rat model of context-based analgesia, where two different contexts (dark and bright) were matched with a high (52°C) or low (48°C) temperature in the hot-plate test during training. Before and after training, we set the temperature to the high level in both contexts. Rats showed longer paw licking latencies in trials with the context originally matched to a low temperature than those to a high temperature, indicating successful establishment of a context-based analgesic effect in rats. This effect was blocked by intraperitoneal injection of naloxone (an opioid receptor antagonist) before the probe. The context-based analgesic effect also disappeared after optogenetic activation or inhibition of the bilateral infralimbic or prelimbic sub-region of the prefrontal cortex. In brief, we established a context-based, non-drug dependent, placebo-like analgesia model in the rat. This model provides a new and useful tool for investigating the cognitive modulation of pain.
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15
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Zeng Y, Hu D, Yang W, Hayashinaka E, Wada Y, Watanabe Y, Zeng Q, Cui Y. A voxel-based analysis of neurobiological mechanisms in placebo analgesia in rats. Neuroimage 2018; 178:602-612. [DOI: 10.1016/j.neuroimage.2018.06.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/22/2018] [Accepted: 06/04/2018] [Indexed: 12/19/2022] Open
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16
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Gertsch J. The Intricate Influence of the Placebo Effect on Medical Cannabis and Cannabinoids. Med Cannabis Cannabinoids 2018; 1:60-64. [PMID: 34676323 PMCID: PMC8489322 DOI: 10.1159/000489291] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 04/17/2018] [Indexed: 09/08/2023] Open
Abstract
The botanical drug cannabis flos (inflorescence of Cannabis sativa L.) has a unique popular status as being a potent recreational drug and bona fide universal remedy (panacea). Generally, cannabinoids exert therapeutic effects in a broad range of pathophysiologies related to inflammation, pain, metabolic and stress-related conditions in preclinical animal models. However, the translation of such data to humans still lacks an evidence-based foundation. Motivated by the booming cannabis manufacturing industry and the increasing worldwide self-therapy by patients, there are cumulative accounts about broad therapeutic effects of cannabis and legal cannabinoids like cannabidiol (CBD) beyond statistical evidence. The numerous affirming anecdotal reports by patients pose a challenge to physicians and legal authorities. Moreover, the lack of standardization of cannabis products and widely missing randomized double-blind placebo-controlled clinical trials largely hinder the scientific assessment of medical cannabis in humans. Given the recent insight that the endocannabinoid system is mediating, at least in part, a placebo effect, psychoactive cannabis and cannabinoids could exert complex neuropharmacological actions. As discussed in this commentary, the meaning response may play a role in the broad palliative and therapeutic effects of medical cannabis unprecedented by other phytopharmaceuticals.
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Affiliation(s)
- Jürg Gertsch
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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17
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Placebo Analgesia in Rodents: Current and Future Research. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2018; 138:1-15. [PMID: 29681320 DOI: 10.1016/bs.irn.2018.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The investigation of placebo effects in animal pain models has received less attention than human research. This may be related to a number of difficulties, including the fact that animals lack the ability to use language and establish expectancies verbally, that animals cannot report and rate the extent to which they experience pain, and the inadequacy of current models of pain. Here, we describe the relatively small number of studies that have been published, communicating the opportunities and excitement of this research. We critically discuss pitfalls and limitations with the hope that this will advance future animal placebo-related research.
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The Underestimated Significance of Conditioning in Placebo Hypoalgesia and Nocebo Hyperalgesia. Pain Res Manag 2018; 2018:6841985. [PMID: 29670678 PMCID: PMC5833150 DOI: 10.1155/2018/6841985] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 12/20/2017] [Indexed: 02/07/2023]
Abstract
Placebo and nocebo effects are intriguing phenomena in pain perception with important implications for clinical research and practice because they can alleviate or increase pain. According to current theoretical accounts, these effects can be shaped by verbal suggestions, social observational learning, and classical conditioning and are necessarily mediated by explicit expectation. In this review, we focus on the contribution of conditioning in the induction of placebo hypoalgesia and nocebo hyperalgesia and present accumulating evidence that conditioning independent from explicit expectation can cause these effects. Especially studies using subliminal stimulus presentation and implicit conditioning (i.e., without contingency awareness) that bypass the development of explicit expectation suggest that conditioning without explicit expectation can lead to placebo and nocebo effects in pain perception. Because only few studies have investigated clinical samples, the picture seems less clear when it comes to patient populations with chronic pain. However, conditioning appears to be a promising means to optimize treatment. In order to get a better insight into the mechanisms of placebo and nocebo effects in pain and the possible benefits of conditioning compared to explicit expectation, future studies should carefully distinguish both methods of induction.
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Schafer SM, Geuter S, Wager TD. Mechanisms of placebo analgesia: A dual-process model informed by insights from cross-species comparisons. Prog Neurobiol 2018; 160:101-122. [PMID: 29108801 PMCID: PMC5747994 DOI: 10.1016/j.pneurobio.2017.10.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 10/24/2017] [Accepted: 10/28/2017] [Indexed: 12/19/2022]
Abstract
Placebo treatments are pharmacologically inert, but are known to alleviate symptoms across a variety of clinical conditions. Associative learning and cognitive expectations both play important roles in placebo responses, however we are just beginning to understand how interactions between these processes lead to powerful effects. Here, we review the psychological principles underlying placebo effects and our current understanding of their brain bases, focusing on studies demonstrating both the importance of cognitive expectations and those that demonstrate expectancy-independent associative learning. To account for both forms of placebo analgesia, we propose a dual-process model in which flexible, contextually driven cognitive schemas and attributions guide associative learning processes that produce stable, long-term placebo effects. According to this model, the placebo-induction paradigms with the most powerful effects are those that combine reinforcement (e.g., the experience of reduced pain after placebo treatment) with suggestions and context cues that disambiguate learning by attributing perceived benefit to the placebo. Using this model as a conceptual scaffold, we review and compare neurobiological systems identified in both human studies of placebo analgesia and behavioral pain modulation in rodents. We identify substantial overlap between the circuits involved in human placebo analgesia and those that mediate multiple forms of context-based modulation of pain behavior in rodents, including forebrain-brainstem pathways and opioid and cannabinoid systems in particular. This overlap suggests that placebo effects are part of a set of adaptive mechanisms for shaping nociceptive signaling based on its information value and anticipated optimal response in a given behavioral context.
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Affiliation(s)
- Scott M Schafer
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA
| | - Stephan Geuter
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA; Institute of Cognitive Science, University of Colorado Boulder, 344 UCB, Boulder, CO 80309, USA; Department of Biostatistics, Johns Hopkins University, 615 N Wolfe St, Baltimore, MD 21205, USA
| | - Tor D Wager
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA; Institute of Cognitive Science, University of Colorado Boulder, 344 UCB, Boulder, CO 80309, USA.
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20
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Novel designs and paradigms to study the placebo response in gastroenterology. Curr Opin Pharmacol 2017; 37:72-79. [PMID: 29102743 DOI: 10.1016/j.coph.2017.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 10/04/2017] [Accepted: 10/06/2017] [Indexed: 12/18/2022]
Abstract
The investigation of the placebo and the nocebo effect and their mechanisms has a rather short history of less than 20 years, especially in gastroenterology, and only the last 5 years have resulted in substantial improvement of understanding. Placebo refers to symptom improvement following a treatment, nocebo to the opposite, symptom worsening. Among the factors driving this progress are traditional psychological models derived from learning (conditioning) theory bridging into clinical science, new animal models to investigate the pharmacology of placebo analgesia, and novel study designs to overcome limitations of traditional randomized and placebo-controlled study designs in drug testing. These are explored here for their implementation and application in gastroenterology, with a focus on visceral pain and nausea.
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Sex differences in mouse Transient Receptor Potential Cation Channel, Subfamily M, Member 8 expressing trigeminal ganglion neurons. PLoS One 2017; 12:e0176753. [PMID: 28472061 PMCID: PMC5417611 DOI: 10.1371/journal.pone.0176753] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 04/17/2017] [Indexed: 01/04/2023] Open
Abstract
The detection of cool temperatures is thought to be mediated by primary afferent neurons that express the cool temperature sensing protein Transient Receptor Potential Cation Channel, Subfamily M, Member 8 (TRPM8). Using mice, this study tested the hypothesis that sex differences in sensitivity to cool temperatures were mediated by differences in neurons that express TRPM8. Ion currents from TRPM8 expressing trigeminal ganglion (TRG) neurons in females demonstrated larger hyperpolarization-activated cyclic nucleotide-gated currents (Ih) than male neurons at both 30° and 18°C. Additionally, female neurons' voltage gated potassium currents (Ik) were suppressed by cooling, whereas male Ik was not significantly affected. At the holding potential tested (-60mV) TRPM8 currents were not visibly activated in either sex by cooling. Modeling the effect of Ih and Ik on membrane potentials demonstrated that at 30° the membrane potential in both sexes is unstable. At 18°, female TRPM8 TRG neurons develop a large oscillating pattern in their membrane potential, whereas male neurons become highly stable. These findings suggest that the differences in Ih and Ik in the TRPM8 TRG neurons of male and female mice likely leads to greater sensitivity of female mice to the cool temperature. This hypothesis was confirmed in an operant reward/conflict assay. Female mice contacted an 18°C surface for approximately half the time that males contacted the cool surface. At 33° and 10°C male and female mice contacted the stimulus for similar amounts of time. These data suggest that sex differences in the functioning of Ih and Ik in TRPM8 expressing primary afferent neurons leads to differences in cool temperature sensitivity.
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Carlino E, Piedimonte A, Benedetti F. Nature of the placebo and nocebo effect in relation to functional neurologic disorders. HANDBOOK OF CLINICAL NEUROLOGY 2017; 139:597-606. [PMID: 27719874 DOI: 10.1016/b978-0-12-801772-2.00048-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Placebos have long been considered a nuisance in clinical research, for they have always been used as comparators for the validation of new treatments. By contrast, today they represent an active field of research, and, due to the involvement of many mechanisms, the study of the placebo effect can actually be viewed as a melting pot of concepts and ideas for neuroscience. There is not a single placebo effect, but many, with different mechanisms across different medical conditions and therapeutic interventions. Expectation, anxiety, and reward are all involved, as well as a variety of learning phenomena and genetic variants. The most productive models to better understand the neurobiology of the placebo effect are pain and Parkinson's disease. In these medical conditions, several neurotransmitters have been identified, such as endogenous opioids, cholecystokinin, dopamine, as well as lipidic mediators, for example, endocannabinoids and prostaglandins. Since the placebo effect is basically a psychosocial context effect, these data indicate that different social stimuli, such as words and therapeutic rituals, may change the chemistry of the patient's brain, and these effects are similar to those induced by drugs.
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Affiliation(s)
- E Carlino
- Department of Neuroscience, University of Turin Medical School, Turin, Italy
| | - A Piedimonte
- Department of Neuroscience, University of Turin Medical School, Turin, Italy
| | - F Benedetti
- Department of Neuroscience, University of Turin Medical School, Turin, Italy; Plateau Rosa Labs, Breuil-Cervinia, Italy and Zermatt, Switzerland.
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Abstract
Placebos are often used by clinicians, usually deceptively and with little rationale or evidence of benefit, making their use ethically problematic. In contrast with their typical current use, a provocative line of research suggests that placebos can be intentionally exploited to extend analgesic therapeutic effects. Is it possible to extend the effects of drug treatments by interspersing placebos? We reviewed a database of placebo studies, searching for studies that indicate that placebos given after repeated administration of active treatments acquire medication-like effects. We found a total of 22 studies in both animals and humans hinting of evidence that placebos may work as a sort of dose extender of active painkillers. Wherever effective in relieving clinical pain, such placebo use would offer several advantages. First, extending the effects of a painkiller through the use of placebos may reduce total drug intake and side effects. Second, dose-extending placebos may decrease patient dependence. Third, using placebos along with active medication, for part of the course of treatment, should limit dose escalation and lower costs. Provided that nondisclosure is preauthorized in the informed consent process and that robust evidence indicates therapeutic benefit comparable to that of standard full-dose therapeutic regimens, introducing dose-extending placebos into the clinical arsenal should be considered. This novel prospect of placebo use has the potential to change our general thinking about painkiller treatments, the typical regimens of painkiller applications, and the ways in which treatments are evaluated.
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24
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Hummel M, Whiteside GT. Measuring and realizing the translational significance of preclinical in vivo studies of painful osteoarthritis. Osteoarthritis Cartilage 2017; 25:376-384. [PMID: 27592040 DOI: 10.1016/j.joca.2016.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 08/15/2016] [Accepted: 08/17/2016] [Indexed: 02/02/2023]
Abstract
In this communication, we discuss some key issues surrounding the translation of preclinical efficacy studies in models of painful osteoarthritis (OA) to the clinical arena. We highlight potential pitfalls which could negatively impact successful translation. These include lack of alignment between a model + endpoint and the intended clinical population, employing testing strategies in animals that are not appropriate for the targeted human population such as pre-emptive treatment and lastly, underestimating the magnitude of the efficacy signal in animals that may be needed to see an effect in the clinical population. Through careful analysis, we highlight the importance of each pitfall by providing relevant examples that will hopefully improve future chances of optimizing translation in the area of OA pain research. We advocate advancing publications directed at comparing methods, outcomes and conclusions between preclinical and clinical studies, regardless of whether the findings are positive or negative, are important for improving the potential for a desired successful translation from the bench to bedside.
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Affiliation(s)
- M Hummel
- Discovery Research, Purdue Pharma L.P., 6 Cedar Brook Drive, Cranbury, NJ 08512, USA
| | - G T Whiteside
- Discovery Research, Purdue Pharma L.P., 6 Cedar Brook Drive, Cranbury, NJ 08512, USA.
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25
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Bayesian prediction of placebo analgesia in an instrumental learning model. PLoS One 2017; 12:e0172609. [PMID: 28225816 PMCID: PMC5321416 DOI: 10.1371/journal.pone.0172609] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 02/06/2017] [Indexed: 02/07/2023] Open
Abstract
Placebo analgesia can be primarily explained by the Pavlovian conditioning paradigm in which a passively applied cue becomes associated with less pain. In contrast, instrumental conditioning employs an active paradigm that might be more similar to clinical settings. In the present study, an instrumental conditioning paradigm involving a modified trust game in a simulated clinical situation was used to induce placebo analgesia. Additionally, Bayesian modeling was applied to predict the placebo responses of individuals based on their choices. Twenty-four participants engaged in a medical trust game in which decisions to receive treatment from either a doctor (more effective with high cost) or a pharmacy (less effective with low cost) were made after receiving a reference pain stimulus. In the conditioning session, the participants received lower levels of pain following both choices, while high pain stimuli were administered in the test session even after making the decision. The choice-dependent pain in the conditioning session was modulated in terms of both intensity and uncertainty. Participants reported significantly less pain when they chose the doctor or the pharmacy for treatment compared to the control trials. The predicted pain ratings based on Bayesian modeling showed significant correlations with the actual reports from participants for both of the choice categories. The instrumental conditioning paradigm allowed for the active choice of optional cues and was able to induce the placebo analgesia effect. Additionally, Bayesian modeling successfully predicted pain ratings in a simulated clinical situation that fits well with placebo analgesia induced by instrumental conditioning.
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Placebo Response is Driven by UCS Revaluation: Evidence, Neurophysiological Consequences and a Quantitative Model. Sci Rep 2016; 6:28991. [PMID: 27436417 PMCID: PMC4951647 DOI: 10.1038/srep28991] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 06/08/2016] [Indexed: 12/19/2022] Open
Abstract
Despite growing scientific interest in the placebo effect and increasing understanding of neurobiological mechanisms, theoretical modeling of the placebo response remains poorly developed. The most extensively accepted theories are expectation and conditioning, involving both conscious and unconscious information processing. However, it is not completely understood how these mechanisms can shape the placebo response. We focus here on neural processes which can account for key properties of the response to substance intake. It is shown that placebo response can be conceptualized as a reaction of a distributed neural system within the central nervous system. Such a reaction represents an integrated component of the response to open substance administration (or to substance intake) and is updated through “unconditioned stimulus (UCS) revaluation learning”. The analysis leads to a theorem, which proves the existence of two distinct quantities coded within the brain, these are the expected or prediction outcome and the reactive response. We show that the reactive response is updated automatically by implicit revaluation learning, while the expected outcome can also be modulated through conscious information processing. Conceptualizing the response to substance intake in terms of UCS revaluation learning leads to the theoretical formulation of a potential neuropharmacological treatment for increasing unlimitedly the effectiveness of a given drug.
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Puviani L, Rama S. A System Computational Model of Implicit Emotional Learning. Front Comput Neurosci 2016; 10:54. [PMID: 27378898 PMCID: PMC4906031 DOI: 10.3389/fncom.2016.00054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 05/23/2016] [Indexed: 12/12/2022] Open
Abstract
Nowadays, the experimental study of emotional learning is commonly based on classical conditioning paradigms and models, which have been thoroughly investigated in the last century. Unluckily, models based on classical conditioning are unable to explain or predict important psychophysiological phenomena, such as the failure of the extinction of emotional responses in certain circumstances (for instance, those observed in evaluative conditioning, in post-traumatic stress disorders and in panic attacks). In this manuscript, starting from the experimental results available from the literature, a computational model of implicit emotional learning based both on prediction errors computation and on statistical inference is developed. The model quantitatively predicts (a) the occurrence of evaluative conditioning, (b) the dynamics and the resistance-to-extinction of the traumatic emotional responses, (c) the mathematical relation between classical conditioning and unconditioned stimulus revaluation. Moreover, we discuss how the derived computational model can lead to the development of new animal models for resistant-to-extinction emotional reactions and novel methodologies of emotions modulation.
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Affiliation(s)
- Luca Puviani
- Department of Engineering “Enzo Ferrari”, University of Modena and Reggio EmiliaModena, Italy
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28
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Rethinking Explicit Expectations: Connecting Placebos, Social Cognition, and Contextual Perception. Trends Cogn Sci 2016; 20:469-480. [PMID: 27108268 DOI: 10.1016/j.tics.2016.04.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 04/01/2016] [Accepted: 04/01/2016] [Indexed: 12/19/2022]
Abstract
Expectancy effects are a widespread phenomenon, and they come with a lasting influence on cognitive operations, from basic stimulus processing to higher cognitive functions. Their impact is often profound and behaviorally significant, as evidenced by an enormous body of literature investigating the characteristics and possible processes underlying expectancy effects. The literature on this topic spans diverse fields, from clinical psychology to cognitive neuroscience, and from social psychology to behavioral biology. We present an emerging perspective on these diverse phenomena and show how this perspective stimulates new toeholds for investigation, provides insight in underlying mechanisms, improves awareness of methodological confounds, and can lead to a deeper understanding of the effects of expectations on a broad spectrum of cognitive processes.
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Lee IS, Lee B, Park HJ, Olausson H, Enck P, Chae Y. A new animal model of placebo analgesia: involvement of the dopaminergic system in reward learning. Sci Rep 2015; 5:17140. [PMID: 26602173 PMCID: PMC4658539 DOI: 10.1038/srep17140] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 10/26/2015] [Indexed: 11/09/2022] Open
Abstract
We suggest a new placebo analgesia animal model and investigated the role of the dopamine and opioid systems in placebo analgesia. Before and after the conditioning, we conducted a conditioned place preference (CPP) test to measure preferences for the cues (Rooms 1 and 2), and a hot plate test (HPT) to measure the pain responses to high level-pain after the cues. In addition, we quantified the expression of tyrosine hydroxylase (TH) in the ventral tegmental area (VTA) and c-Fos in the anterior cingulate cortex (ACC) as a response to reward learning and pain response. We found an enhanced preference for the low level-pain paired cue and enhanced TH expression in the VTA of the Placebo and Placebo + Naloxone groups. Haloperidol, a dopamine antagonist, blocked these effects in the Placebo + Haloperidol group. An increased pain threshold to high-heat pain and reduced c-Fos expression in the ACC were observed in the Placebo group only. Haloperidol blocked the place preference effect, and naloxone and haloperidol blocked the placebo analgesia. Cue preference is mediated by reward learning via the dopamine system, whereas the expression of placebo analgesia is mediated by the dopamine and opioid systems.
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Affiliation(s)
- In-Seon Lee
- Acupuncture and Meridian Science Research Center, College of Korean Medicine, Kyung Hee University, Seoul, Korea.,Department of Internal Medicine: Psychosomatic Medicine and Psychotherapy, University of Tübingen, Tübingen, Germany.,Institute for Medical Psychology, fMEG Center, University of Tübingen, Tübingen, Germany.,IMPRS for Cognitive and Systems Neuroscience, University of Tübingen, Tübingen, Germany
| | - Bombi Lee
- Acupuncture and Meridian Science Research Center, College of Korean Medicine, Kyung Hee University, Seoul, Korea
| | - Hi-Joon Park
- Acupuncture and Meridian Science Research Center, College of Korean Medicine, Kyung Hee University, Seoul, Korea
| | - Håkan Olausson
- Center for Social and Affective Neuroscience, Linköping University
| | - Paul Enck
- Department of Internal Medicine: Psychosomatic Medicine and Psychotherapy, University of Tübingen, Tübingen, Germany
| | - Younbyoung Chae
- Acupuncture and Meridian Science Research Center, College of Korean Medicine, Kyung Hee University, Seoul, Korea
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30
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Anderson EM, Reeves T, Kapernaros K, Neubert JK, Caudle RM. Phosphorylation of the N-methyl-d-aspartate receptor is increased in the nucleus accumbens during both acute and extended morphine withdrawal. J Pharmacol Exp Ther 2015; 355:496-505. [PMID: 26377910 DOI: 10.1124/jpet.115.227629] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 09/08/2015] [Indexed: 11/22/2022] Open
Abstract
Opioid withdrawal causes a dysphoric state that can lead to complications in pain patients and can propagate use in drug abusers and addicts. Opioid withdrawal changes the activity of neurons in the nucleus accumbens, an area rich in both opioid-binding mu opioid receptors and glutamate-binding NMDA receptors. Because the accumbens is an area important for reward and aversion, plastic changes in this area during withdrawal could alter future behaviors in animals. We discovered an increase in phosphorylation of serine 897 in the NR1 subunit of the NMDA receptor (pNR1) during acute morphine withdrawal. This serine can be phosphorylated by protein kinase A (PKA) and dephosphorylated by calcineurin. We next demonstrated that this increased pNR1 change is associated with an increase in NR1 surface expression. NR1 surface expression and pNR1 levels during acute withdrawal were both reduced by the NMDA receptor antagonist MK-801 (dizocilpine hydrogen maleate) and the PKA inhibitor H-89(N-[2-[[3-(4-bromophenyl)-2-propenyl]amino]ethyl]-5-isoquinolinesulfonamide dihydrochloride hydrate). We also found that pNR1 levels remained high after an extended morphine withdrawal period of 2 months, correlated with reward-seeking behavior for palatable food, and were associated with a decrease in accumbal calcineurin levels. These data suggest that NR1 phosphorylation changes during the acute withdrawal phase can be long lasting and may reflect a permanent change in NMDA receptors in the accumbens. These altered NMDA receptors in the accumbens could play a role in long-lasting behaviors associated with reward and opioid use.
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Affiliation(s)
- Ethan M Anderson
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida (E.M.A., R.M.C.); Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida (E.M.A., R.M.C.); University of Florida, Gainesville, Florida (T.R., K.K.); and UF College of Dentistry, Department of Orthodontics, Gainesville, Florida (J.K.N.)
| | - Turi Reeves
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida (E.M.A., R.M.C.); Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida (E.M.A., R.M.C.); University of Florida, Gainesville, Florida (T.R., K.K.); and UF College of Dentistry, Department of Orthodontics, Gainesville, Florida (J.K.N.)
| | - Katherine Kapernaros
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida (E.M.A., R.M.C.); Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida (E.M.A., R.M.C.); University of Florida, Gainesville, Florida (T.R., K.K.); and UF College of Dentistry, Department of Orthodontics, Gainesville, Florida (J.K.N.)
| | - John K Neubert
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida (E.M.A., R.M.C.); Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida (E.M.A., R.M.C.); University of Florida, Gainesville, Florida (T.R., K.K.); and UF College of Dentistry, Department of Orthodontics, Gainesville, Florida (J.K.N.)
| | - Robert M Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida (E.M.A., R.M.C.); Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida (E.M.A., R.M.C.); University of Florida, Gainesville, Florida (T.R., K.K.); and UF College of Dentistry, Department of Orthodontics, Gainesville, Florida (J.K.N.)
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Pepelassi E, Rahiotis C, Peponi E, Kakaboura A, Vrotsos I. Effectiveness of an in-office arginine-calcium carbonate paste on dentine hypersensitivity in periodontitis patients: a double-blind, randomized controlled trial. J Clin Periodontol 2014; 42:37-45. [DOI: 10.1111/jcpe.12319] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Eudoxie Pepelassi
- Department of Periodontology; School of Dentistry; University of Athens; Athens Greece
| | - Christos Rahiotis
- Department of Operative Dentistry; School of Dentistry; University of Athens; Athens Greece
| | - Eleni Peponi
- Department of Periodontology; School of Dentistry; University of Athens; Athens Greece
| | - Afrodite Kakaboura
- Department of Operative Dentistry; School of Dentistry; University of Athens; Athens Greece
| | - Ioannis Vrotsos
- Department of Periodontology; School of Dentistry; University of Athens; Athens Greece
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Abstract
Today we are witnessing a new science of placebo, a complex discipline that encompasses several experimental approaches and translational implications. Modern neurobiological tools have been used to answer important questions in placebo research, such as the top-down modulation of sensory and motor systems as well as the influence of cognition, emotions, and learning on symptoms, diseases, and responses to treatments. What we have learned is that there is not one single placebo effect, but many. This review highlights the translational implications of this new knowledge, ranging from clinical trial design to medical practice to social and ethical issues.
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Affiliation(s)
- Fabrizio Benedetti
- Department of Neuroscience, University of Turin Medical School and National Institute of Neuroscience, 10125 Turin, Italy.
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McNabb CT, White MM, Harris AL, Fuchs PN. The elusive rat model of conditioned placebo analgesia. Pain 2014; 155:2022-32. [PMID: 25026214 DOI: 10.1016/j.pain.2014.07.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 06/30/2014] [Accepted: 07/03/2014] [Indexed: 10/25/2022]
Abstract
Recent research on human placebo analgesia has suggested the need for rodent models to further elucidate the neural substrates of the placebo effect. This series of 3 experiments therefore was performed in an attempt to develop a model of placebo analgesia in rats. In each study, female Sprague-Dawley rats received an L5 spinal nerve ligation to induce a neuropathic pain condition. Each rat then underwent a 4-day conditioning procedure in which an active analgesic drug or its vehicle (unconditioned stimulus) was associated with the following cues (conditioned stimuli): novel testing room (environmental), vanilla scent cue (olfactory), dim incandescent lighting (visual), restraint procedure/injection (tactile), and time of day and injection-test latency (temporal). The analgesics for each experiment were as follows: Experiment 1 used 90 mg/kg gabapentin, experiment 2 used 3mg/kg loperamide hydrochloride, and experiment 3 used 6 mg/kg morphine sulfate. On the following test day, half of the animals received the opposite treatment, resulting in 4 conditioning manipulations: drug/drug, drug/vehicle, vehicle/drug, and vehicle/vehicle. Nociceptive thresholds were assessed with the mechanical paw withdrawal threshold test each day after the conditioning procedure. In all 3 experiments, no significant differences were detected on test day between control and placebo groups, indicating a lack of a conditioned placebo analgesic response. Our results contrast with prior research that implies the existence of a reliable and robust response to placebo treatment. We conclude that placebo analgesia in rats is not particularly robust and that it is difficult to achieve using conventional procedures and proper experimental design.
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Affiliation(s)
| | - Michelle M White
- Department of Psychology, University of Texas at Arlington, Arlington, TX, USA
| | - Amber L Harris
- Department of Psychology, University of Texas at Arlington, Arlington, TX, USA
| | - Perry N Fuchs
- Department of Psychology, University of Texas at Arlington, Arlington, TX, USA; Department of Biology, University of Texas at Arlington, Arlington, TX, USA.
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34
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Shah E, Pimentel M. Placebo effect in clinical trial design for irritable bowel syndrome. J Neurogastroenterol Motil 2014; 20:163-70. [PMID: 24840369 PMCID: PMC4015207 DOI: 10.5056/jnm.2014.20.2.163] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Revised: 10/26/2013] [Accepted: 11/03/2013] [Indexed: 12/15/2022] Open
Abstract
Ongoing efforts to improve clinical trial design in irritable bowel syndrome have been hindered by high placebo response rates and ineffective outcome measures. We assessed established strategies to minimize placebo effect as well as the various approaches to placebo effect which can affect trial design. These include genetic markers such as catechol-O-methyltransferase, opioidergic and dopaminergic neurobiologic theory, pre-cebo effect centered on expectancy theory, and side effect unblinding grounded on conditioning theory. We reviewed endpoints used in the study of IBS over the past decade including adequate relief and subjective global relief, emphasizing their weaknesses in fully evaluating the IBS condition, specifically their motility effects based on functional net value and relative benefit-harm based on dropouts due to adverse events. The focus of this review is to highlight ongoing efforts to improve clinical trial design which can lead to better outcomes in a real-world setting.
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Affiliation(s)
- Eric Shah
- GI Motility Program, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Mark Pimentel
- GI Motility Program, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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36
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Abstract
Pain is a sensory and emotional experience that is substantially modulated by psychological, social and contextual factors. Research now indicates that the influence of these factors is even more powerful than expected and involves the therapeutic response to analgesic drugs as well as the pain experience itself, which in some circumstances can even be a form of reward. Different experimental approaches and models, both in the laboratory and in the clinical setting, have been used to better characterize and understand the complex neurobiology of pain modulation. These approaches include placebo analgesia, nocebo hyperalgesia, hidden administration of analgesics, and the manipulation of the pain-reward relationship. Overall, these studies show that different neurochemical systems are activated in different positive and negative contexts. Moreover, pain can activate reward mechanisms when experienced within contexts that have special positive meaning. Because routine medical practice usually takes place in contexts that use different rituals, these neurobiological insights might have profound clinical implications.
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Affiliation(s)
- Elisa Carlino
- Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience, Corso Raffaello 30, 10125 Turin, Italy
| | - Elisa Frisaldi
- Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience, Corso Raffaello 30, 10125 Turin, Italy
| | - Fabrizio Benedetti
- Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience, Corso Raffaello 30, 10125 Turin, Italy
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37
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Anderson EM, Jenkins AC, Caudle RM, Neubert JK. The effects of a co-application of menthol and capsaicin on nociceptive behaviors of the rat on the operant orofacial pain assessment device. PLoS One 2014; 9:e89137. [PMID: 24558480 PMCID: PMC3928399 DOI: 10.1371/journal.pone.0089137] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 01/20/2014] [Indexed: 01/04/2023] Open
Abstract
Background Transient receptor potential (TRP) cation channels are involved in the perception of hot and cold pain and are targets for pain relief in humans. We hypothesized that agonists of TRPV1 and TRPM8/TRPA1, capsaicin and menthol, would alter nociceptive behaviors in the rat, but their opposite effects on temperature detection would attenuate one another if combined. Methods Rats were tested on the Orofacial Pain Assessment Device (OPAD, Stoelting Co.) at three temperatures within a 17 min behavioral session (33°C, 21°C, 45°C). Results The lick/face ratio (L/F: reward licking events divided by the number of stimulus contacts. Each time there is a licking event a contact is being made.) is a measure of nociception on the OPAD and this was equally reduced at 45°C and 21°C suggesting they are both nociceptive and/or aversive to rats. However, rats consumed (licks) equal amounts at 33°C and 21°C but less at 45°C suggesting that heat is more nociceptive than cold at these temperatures in the orofacial pain model. When menthol and capsaicin were applied alone they both induced nociceptive behaviors like lower L/F ratios and licks. When applied together though, the licks at 21°C were equal to those at 33°C and both were significantly higher than at 45°C. Conclusions This suggests that the cool temperature is less nociceptive when TRPM8/TRPA1 and TRPV1 are co-activated. These results suggest that co-activation of TRP channels can reduce certain nociceptive behaviors. These data demonstrate that the motivational aspects of nociception can be influenced selectively by TRP channel modulation and that certain aspects of pain can be dissociated and therefore targeted selectively in the clinic.
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Affiliation(s)
- Ethan M. Anderson
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida, United States of America
- Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida, United States of America
- * E-mail:
| | - Alan C. Jenkins
- Department of Orthodontics, University of Florida, Gainesville, Florida, United States of America
| | - Robert M. Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Florida, United States of America
- Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, Florida, United States of America
| | - John K. Neubert
- Department of Orthodontics, University of Florida, Gainesville, Florida, United States of America
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Murphy NP, Mills RH, Caudle RM, Neubert JK. Operant assays for assessing pain in preclinical rodent models: highlights from an orofacial assay. Curr Top Behav Neurosci 2014; 20:121-45. [PMID: 25103871 DOI: 10.1007/7854_2014_332] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Despite an immense investment of resources, pain remains at epidemic proportions. Given this, there has been an increased effort toward appraising the process by which new painkillers are developed, focusing specifically on why so few analgesics make it from the benchside to the bedside. The use of behavioral assays and animal modeling for the preclinical stages of analgesic development is being reexamined to determine whether they are truly relevant, meaningful, and predictive. Consequently, there is a strengthening consensus that the traditional reflex-based assays upon which several decades of preclinical pain research has been based are inadequate. Thus, investigators have recently turned to the development of new preclinical assays with improved face, content, and predictive validity. In this regard, operant pain assays show considerable promise, as they are more sensitive, present better validity, and, importantly, better encompass the psychological and affective dimensions of pain that trouble human pain sufferers. Here, we briefly compare and contrast reflex assays with operant assays, and we introduce a particular operant orofacial pain assay used in a variety of experiments to emphasize how operant pain assays can be applied to preclinical studies of pain.
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Affiliation(s)
- Niall P Murphy
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, USA,
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39
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Abstract
This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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40
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Mustafa G, Anderson EM, Bokrand-Donatelli Y, Neubert JK, Caudle RM. Anti-nociceptive effect of a conjugate of substance P and light chain of botulinum neurotoxin type A. Pain 2013; 154:2547-2553. [PMID: 23933181 DOI: 10.1016/j.pain.2013.07.041] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 06/26/2013] [Accepted: 07/23/2013] [Indexed: 10/26/2022]
Abstract
Neuropathic pain is a debilitating condition resulting from damage to sensory transmission pathways in the peripheral and central nervous system. A potential new way of treating chronic neuropathic pain is to target specific pain-processing neurons based on their expression of particular receptor molecules. We hypothesized that a toxin-neuropeptide conjugate would alter pain by first being taken up by specific receptors for the neuropeptide expressed on the neuronal cells. Then, once inside the cell the toxin would inhibit the neurons' activity without killing the neurons, thereby providing pain relief without lesioning the nervous system. In an effort to inactivate the nociceptive neurons in the trigeminal nucleus caudalis in mice, we targeted the NK1 receptor (NK1R) using substance P (SP). The catalytically active light chain of botulinum neurotoxin type A (LC/A) was conjugated with SP. Our results indicate that the conjugate BoNT/A-LC:SP is internalized in cultured NK1R-expressing neurons and also cleaves the target of botulinum toxin, a component-docking motif necessary for release of neurotransmitters called SNAP-25. The conjugate was next tested in a murine model of Taxol-induced neuropathic pain. An intracisternal injection of BoNT/A-LC:SP decreased thermal hyperalgesia as measured by the operant orofacial nociception assay. These findings indicate that conjugates of the light chain of botulinum toxin are extremely promising agents for use in suppressing neuronal activity for extended time periods, and that BoNT/A-LC:SP may be a useful agent for treating chronic pain.
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Affiliation(s)
- Golam Mustafa
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, FL, USA Department of Neuroscience, University of Florida College of Medicine, McKnight Brain Institute, Gainesville, FL, USA Department of Orthodontics, University of Florida, Gainesville, FL, USA
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Murray D, Stoessl AJ. Mechanisms and therapeutic implications of the placebo effect in neurological and psychiatric conditions. Pharmacol Ther 2013; 140:306-18. [PMID: 23880289 DOI: 10.1016/j.pharmthera.2013.07.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 07/09/2013] [Indexed: 12/19/2022]
Abstract
The power of a placebo to effect clinically meaningful neurobiological change comparable to pharmacological therapies has been demonstrated, although the mechanisms are not fully understood. Predicting placebo responsiveness has only recently received more attention, but psychological disposition, contextual and biological factors are now known to dramatically affect a person's susceptibility to the placebo effect. The placebo effect depends upon expectancies that can be modified in a number of ways, including conditioning through explicit or implicit learned associations. Based on the dopaminergic response to anticipation of benefit in Parkinson's disease, it was suggested that the placebo effect can be seen as analogous to the expectation of reward. Dopaminergic pathways have since been implicated in the placebo response in pain and depression. Additionally, endogenous opioid release is known to mediate many forms of placebo analgesia. We provide an overview of the mechanisms and the therapeutic implications of the placebo effect in neurological and psychiatric conditions. We include evidence for detrimental effects arising from seemingly inert interventions, termed the 'nocebo effect.' Neuroimaging has critically advanced the study of the placebo effect and provides some of the strongest evidence for the mechanisms of this phenomenon prevalent across an array of human health-related circumstances. This review specifically focuses on mechanisms of the placebo effect in the three conditions that have most significantly demonstrated this effect and for which a plausible physiological basis can be identified: pain, PD and depression. Other neurological and psychiatric diseases reviewed include multiple sclerosis, Huntington's disease, Alzheimer's disease, schizophrenia and epilepsy.
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Affiliation(s)
- Danielle Murray
- Pacific Parkinson's Research Centre and Department of Medicine, Division of Neurology, University of British Columbia & Vancouver Coastal Health, Canada
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42
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Abstract
Modern medicine has progressed in parallel with the advancement of biochemistry, anatomy, and physiology. By using the tools of modern medicine, the physician today can treat and prevent a number of diseases through pharmacology, genetics, and physical interventions. Besides this materia medica, the patient's mind, cognitions, and emotions play a central part as well in any therapeutic outcome, as investigated by disciplines such as psychoneuroendocrinoimmunology. This review describes recent findings that give scientific evidence to the old tenet that patients must be both cured and cared for. In fact, we are today in a good position to investigate complex psychological factors, like placebo effects and the doctor-patient relationship, by using a physiological and neuroscientific approach. These intricate psychological factors can be approached through biochemistry, anatomy, and physiology, thus eliminating the old dichotomy between biology and psychology. This is both a biomedical and a philosophical enterprise that is changing the way we approach and interpret medicine and human biology. In the first case, curing the disease only is not sufficient, and care of the patient is of tantamount importance. In the second case, the philosophical debate about the mind-body interaction can find some important answers in the study of placebo effects. Therefore, maybe paradoxically, the placebo effect and the doctor-patient relationship can be approached by using the same biochemical, cellular and physiological tools of the materia medica, which represents an epochal transition from general concepts such as suggestibility and power of mind to a true physiology of the doctor-patient interaction.
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Affiliation(s)
- Fabrizio Benedetti
- Department of Neuroscience, University of Turin Medical School, and National Institute of Neuroscience, Turin, Italy.
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43
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Anderson EM, Mills R, Nolan TA, Jenkins AC, Mustafa G, Lloyd C, Caudle RM, Neubert JK. Use of the Operant Orofacial Pain Assessment Device (OPAD) to measure changes in nociceptive behavior. J Vis Exp 2013:e50336. [PMID: 23792907 DOI: 10.3791/50336] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We present an operant system for the detection of pain in awake, conscious rodents. The Orofacial Pain Assessment Device (OPAD) assesses pain behaviors in a more clinically relevant way by not relying on reflex-based measures of nociception. Food fasted, hairless (or shaved) rodents are placed into a Plexiglas chamber which has two Peltier-based thermodes that can be programmed to any temperature between 7 °C and 60 °C. The rodent is trained to make contact with these in order to access a reward bottle. During a session, a number of behavioral pain outcomes are automatically recorded and saved. These measures include the number of reward bottle activations (licks) and facial contact stimuli (face contacts), but custom measures like the lick/face ratio (total number of licks per session/total number of contacts) can also be created. The stimulus temperature can be set to a single temperature or multiple temperatures within a session. The OPAD is a high-throughput, easy to use operant assay which will lead to better translation of pain research in the future as it includes cortical input instead of relying on spinal reflex-based nociceptive assays.
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Affiliation(s)
- Ethan M Anderson
- Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry.
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45
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Price DD. The inner experience and neurobiology of placebo analgesia. Can these perspectives be integrated? Pain 2013; 154:328-329. [PMID: 23333053 DOI: 10.1016/j.pain.2012.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 12/13/2012] [Accepted: 12/14/2012] [Indexed: 11/29/2022]
Affiliation(s)
- Donald D Price
- Division of Neuroscience, Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, Florida, USA
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46
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Benedetti F. Placebo responses in animals. Pain 2012; 153:1983-1984. [PMID: 22766357 DOI: 10.1016/j.pain.2012.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 06/08/2012] [Accepted: 06/08/2012] [Indexed: 11/30/2022]
Affiliation(s)
- Fabrizio Benedetti
- Department of Neuroscience, University of Turin Medical School, National Institute of Neuroscience, Corso Raffaello 30, 10125 Turin, Italy Tel.: +39 011 670 8492
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