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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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Karimi SA, Zahra FT, Martin LJ. IUPHAR review: Navigating the role of preclinical models in pain research. Pharmacol Res 2024; 200:107073. [PMID: 38232910 DOI: 10.1016/j.phrs.2024.107073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/09/2024] [Accepted: 01/11/2024] [Indexed: 01/19/2024]
Abstract
Chronic pain is a complex and challenging medical condition that affects millions of people worldwide. Understanding the underlying mechanisms of chronic pain is a key goal of preclinical pain research so that more effective treatment strategies can be developed. In this review, we explore nociception, pain, and the multifaceted factors that lead to chronic pain by focusing on preclinical models. We provide a detailed look into inflammatory and neuropathic pain models and discuss the most used animal models for studying the mechanisms behind these conditions. Additionally, we emphasize the vital role of these preclinical models in developing new pain-relief drugs, focusing on biologics and the therapeutic potential of NMDA and cannabinoid receptor antagonists. We also discuss the challenges of TRPV1 modulation for pain treatment, the clinical failures of neurokinin (NK)- 1 receptor antagonists, and the partial success story of Ziconotide to provide valuable lessons for preclinical pain models. Finally, we highlight the overall success and limitations of current treatments for chronic pain while providing critical insights into the development of more effective therapies to alleviate the burden of chronic pain.
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Affiliation(s)
- Seyed Asaad Karimi
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Fatama Tuz Zahra
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Loren J Martin
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada; Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.
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