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Cerqueira-Nunes M, Monteiro C, Galhardo V, Cardoso-Cruz H. Orbitostriatal encoding of reward delayed gratification and impulsivity in chronic pain. Brain Res 2024; 1839:149044. [PMID: 38821332 DOI: 10.1016/j.brainres.2024.149044] [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: 01/12/2024] [Revised: 05/17/2024] [Accepted: 05/28/2024] [Indexed: 06/02/2024]
Abstract
Central robust network functional rearrangement is a characteristic of several neurological conditions, including chronic pain. Preclinical and clinical studies have shown the importance of pain-induced dysfunction in both orbitofrontal cortex (OFC) and nucleus accumbens (NAc) brain regions for the emergence of cognitive deficits. Outcome information processing recruits the orbitostriatal circuitry, a pivotal pathway regarding context-dependent reward value encoding. The current literature reveals the existence of structural and functional changes in the orbitostriatal crosstalk in chronic pain conditions, which have emerged as a possible underlying cause for reward and time discrimination impairments observed in individuals affected by such disturbances. However, more comprehensive investigations are needed to elucidate the underlying disturbances that underpin disease development. In this review article, we aim to provide a comprehensive view of the orbitostriatal mechanisms underlying time-reward dependent behaviors, and integrate previous findings on local and network malplasticity under the framework of the chronic pain sphere.
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Affiliation(s)
- Mariana Cerqueira-Nunes
- Instituto de Investigação e Inovação em Saúde (i3S) - Pain Neurobiology Group, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Faculdade de Medicina, Departamento de Biomedicina - Unidade de Biologia Experimental (FMUP), Universidade do Porto, Rua Doutor Plácido da Costa, 4200-450 Porto, Portugal; Programa doutoral em Neurociências (PDN), Faculdade de Medicina, Universidade do Porto, Rua Doutor Plácido da Costa, 4200-450 Porto, Portugal
| | - Clara Monteiro
- Instituto de Investigação e Inovação em Saúde (i3S) - Pain Neurobiology Group, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Faculdade de Medicina, Departamento de Biomedicina - Unidade de Biologia Experimental (FMUP), Universidade do Porto, Rua Doutor Plácido da Costa, 4200-450 Porto, Portugal
| | - Vasco Galhardo
- Instituto de Investigação e Inovação em Saúde (i3S) - Pain Neurobiology Group, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Faculdade de Medicina, Departamento de Biomedicina - Unidade de Biologia Experimental (FMUP), Universidade do Porto, Rua Doutor Plácido da Costa, 4200-450 Porto, Portugal
| | - Helder Cardoso-Cruz
- Instituto de Investigação e Inovação em Saúde (i3S) - Pain Neurobiology Group, Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal; Faculdade de Medicina, Departamento de Biomedicina - Unidade de Biologia Experimental (FMUP), Universidade do Porto, Rua Doutor Plácido da Costa, 4200-450 Porto, Portugal.
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Delignat-Lavaud B, Kano J, Ducrot C, Massé I, Mukherjee S, Giguère N, Moquin L, Lévesque C, Burke S, Denis R, Bourque MJ, Tchung A, Rosa-Neto P, Lévesque D, De Beaumont L, Trudeau LÉ. Synaptotagmin-1-dependent phasic axonal dopamine release is dispensable for basic motor behaviors in mice. Nat Commun 2023; 14:4120. [PMID: 37433762 PMCID: PMC10336101 DOI: 10.1038/s41467-023-39805-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 06/27/2023] [Indexed: 07/13/2023] Open
Abstract
In Parkinson's disease (PD), motor dysfunctions only become apparent after extensive loss of DA innervation. This resilience has been hypothesized to be due to the ability of many motor behaviors to be sustained through a diffuse basal tone of DA; but experimental evidence for this is limited. Here we show that conditional deletion of the calcium sensor synaptotagmin-1 (Syt1) in DA neurons (Syt1 cKODA mice) abrogates most activity-dependent axonal DA release in the striatum and mesencephalon, leaving somatodendritic (STD) DA release intact. Strikingly, Syt1 cKODA mice showed intact performance in multiple unconditioned DA-dependent motor tasks and even in a task evaluating conditioned motivation for food. Considering that basal extracellular DA levels in the striatum were unchanged, our findings suggest that activity-dependent DA release is dispensable for such tasks and that they can be sustained by a basal tone of extracellular DA. Taken together, our findings reveal the striking resilience of DA-dependent motor functions in the context of a near-abolition of phasic DA release, shedding new light on why extensive loss of DA innervation is required to reveal motor dysfunctions in PD.
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Affiliation(s)
- Benoît Delignat-Lavaud
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Jana Kano
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Charles Ducrot
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Ian Massé
- Hôpital du Sacré-Cœur-de-Montréal, CIUSSS NIM, Université de Montréal, Montreal, QC, Canada
| | - Sriparna Mukherjee
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, 20815, USA
| | - Nicolas Giguère
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Luc Moquin
- Centre intégré universitaire de santé et de services sociaux (CIUSSS) de l'Ouest-de-l'Île-de-Montréal; Department of Neurology and Neurosurgery, Psychiatry and Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
| | | | - Samuel Burke
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Raphaëlle Denis
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Marie-Josée Bourque
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, 20815, USA
| | - Alex Tchung
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada
| | - Pedro Rosa-Neto
- Centre intégré universitaire de santé et de services sociaux (CIUSSS) de l'Ouest-de-l'Île-de-Montréal; Department of Neurology and Neurosurgery, Psychiatry and Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
| | - Daniel Lévesque
- Faculty of Pharmacy, Université de Montréal, Montreal, QC, Canada
| | - Louis De Beaumont
- Hôpital du Sacré-Cœur-de-Montréal, CIUSSS NIM, Université de Montréal, Montreal, QC, Canada
| | - Louis-Éric Trudeau
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
- Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
- SNC and CIRCA Research Groups, Université de Montréal, Montréal, QC, Canada.
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, 20815, USA.
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3
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Huang M, Wang G, Lin Y, Guo Y, Ren X, Shao J, Cao J, Zang W, Li Z. Dopamine receptor D2, but not D1, mediates the reward circuit from the ventral tegmental area to the central amygdala, which is involved in pain relief. Mol Pain 2022; 18:17448069221145096. [PMID: 36464669 PMCID: PMC9742700 DOI: 10.1177/17448069221145096] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pain involves both sensory and affective dimensions. The amygdala is a key player in linking nociceptive stimuli to negative emotional behaviors or affective states. Relief of pain is rewarding and activates brain reward circuits. Whether the reward circuit from the ventral tegmental area (VTA) to the central amygdala (CeA) is involved in pain relief remains unexplored. Using a model of experimental postsurgical pain, we found that pain relief elicited conditioned place preference (CPP), activated CeA-projecting dopaminergic cells in the VTA, and decreased dopaminergic D2 receptor expression in the CeA. Activation of the VTA-CeA neural pathway using optogenetic approaches relieved incisional pain. Administration of a D2 receptor agonist reversed the pain relief elicited by light-induced activation of the VTA-CeA pathway. These findings indicate that the VTA-CeA circuit is involved in pain relief in mice via dopamine receptor D2 in the CeA.
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Affiliation(s)
- Minjie Huang
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China,Department of Human Anatomy, Basic Medical Sciences College, Sanquan College of Xinxiang Medical University, Xinxiang, China
| | - Guoqing Wang
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China,Department of Neurosurgery, West China Hospital, West China Medical School, Sichuan University, Chengdu, China
| | - Yazhou Lin
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China
| | - Yanyan Guo
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China
| | - Xiuhua Ren
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China
| | - Jinping Shao
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China
| | - Jing Cao
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China
| | - Weidong Zang
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China
| | - Zhihua Li
- Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, Zhengzhou, Henan Province, China,Zhihua Li, Department of Human Anatomy, Basic Medical Sciences College, Zhengzhou University, 1 Science Road, Zhengzhou 450001, Henan Province, China.
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Frederick NM, Pooler MM, Shah P, Didonna A, Opal P. Pharmacological perturbation reveals deficits in D2 receptor responses in Thap1 null mice. Ann Clin Transl Neurol 2021; 8:2302-2308. [PMID: 34802187 PMCID: PMC8670318 DOI: 10.1002/acn3.51481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/28/2021] [Accepted: 10/30/2021] [Indexed: 11/17/2022] Open
Abstract
The primary dystonia DYT6 is caused by mutations in the transcription factor Thanatos‐associated protein 1 (THAP1). To understand THAP1’s functions, we generated mice lacking THAP1 in the nervous system. THAP1 loss causes locomotor deficits associated with transcriptional changes. Since many of the genes misregulated involve dopaminergic signaling, we pharmacologically challenged the two striatal canonical dopamine pathways: the direct, regulated by the D1 receptor, and the indirect, regulated by the D2 receptor. We discovered that depleting THAP1 specifically interferes with the D2 receptor responses, pointing to a selective misregulation of the indirect pathway in DYT6 with implications for pathogenesis and treatment.
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Affiliation(s)
- Natalie M Frederick
- Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA.,Northwestern University Interdepartmental Neuroscience Program, Northwestern University, Evanston, Illinois, 60208, USA
| | - Morgan M Pooler
- Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA
| | - Parth Shah
- Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA
| | - Alessandro Didonna
- Department of Neurology, Weill Institute for Neurosciences, University of California San Francisco, San Francisco, California, 94158, USA
| | - Puneet Opal
- Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA.,Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, 60611, USA
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5
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The Distinct Functions of Dopaminergic Receptors on Pain Modulation: A Narrative Review. Neural Plast 2021; 2021:6682275. [PMID: 33688340 PMCID: PMC7920737 DOI: 10.1155/2021/6682275] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/06/2021] [Accepted: 02/09/2021] [Indexed: 12/18/2022] Open
Abstract
Chronic pain is considered an economic burden on society as it often results in disability, job loss, and early retirement. Opioids are the most common analgesics prescribed for the management of moderate to severe pain. However, chronic exposure to these drugs can result in opioid tolerance and opioid-induced hyperalgesia. On pain modulation strategies, exploiting the multitarget drugs with the ability of the superadditive or synergistic interactions attracts more attention. In the present report, we have reviewed the analgesic effects of different dopamine receptors, particularly D1 and D2 receptors, in different regions of the central nervous system, including the spinal cord, striatum, nucleus accumbens (NAc), and periaqueductal gray (PAG). According to the evidence, these regions are not only involved in pain modulation but also express a high density of DA receptors. The findings can be categorized as follows: (1) D2-like receptors may exert a higher analgesic potency, but D1-like receptors act in different manners across several mechanisms in the mentioned regions; (2) in the spinal cord and striatum, antinociception of DA is mainly mediated by D2-like receptors, while in the NAc and PAG, both D1- and D2-like receptors are involved as analgesic targets; and (3) D2-like receptor agonists can act as adjuvants of μ-opioid receptor agonists to potentiate analgesic effects and provide a better approach to pain relief.
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6
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Dopamine D 1 and D 2 receptors mediate analgesic and hypnotic effects of l-tetrahydropalmatine in a mouse neuropathic pain model. Psychopharmacology (Berl) 2019; 236:3169-3182. [PMID: 31172225 DOI: 10.1007/s00213-019-05275-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 05/10/2019] [Indexed: 12/21/2022]
Abstract
RATIONALE Levo-tetrahydropalmatine (l-THP), an active ingredient of Corydalis yanhusuo, has been reported to be a partial agonist for dopamine D1 receptors (D1R) and an antagonist for D2R. Although it has been safely used clinically in China for decades as an analgesic with sedative/hypnotic properties, there are few studies that address the mechanisms by which l-THP exerts its beneficial effects in chronic pain-induced sleep disturbance. OBJECTIVES To investigate the effects and mechanisms of l-THP on sleep disturbance in a neuropathic pain-like condition. METHODS A mouse model of chronic neuropathic pain induced by partial sciatic nerve ligation (PSNL) was employed. The antinociceptive and hypnotic effects of l-THP were evaluated by measurement of mechanical allodynia, thermal hyperalgesia, and electroencephalogram (EEG) recordings in PSNL mice. Pharmacological approaches and c-Fos expression were used to clarify the mechanisms of l-THP. RESULTS Intraperitoneal injection of l-THP at 5 and 10 mg/kg not only significantly increased the mechanical threshold by 134.4% and 174.8%, and prolonged the thermal latency by 49.4% and 69.2%, but also increased non-rapid eye movement sleep by 17.5% and 29.6%, and decreased sleep fragmentation in PSNL mice, compared with the vehicle control. Moreover, the antinociceptive effect of l-THP was prevented by D1R antagonist SCH23390 or D2R agonist quinpirole; meanwhile, the hypnotic effect of l-THP was blocked by quinpirole rather than by SCH23390. Immunohistochemistry demonstrated that l-THP inhibited c-Fos overexpression induced by PSNL in the cingulate cortex and the periaqueductal gray. CONCLUSIONS These findings indicated that l-THP exerted analgesic effects by agonism D1R and antagonism D2R, and the antagonism of D2R mediated the hypnotic effect of l-THP in PSNL mice.
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Cardoso-Cruz H, Dourado M, Monteiro C, Galhardo V. Blockade of dopamine D2 receptors disrupts intrahippocampal connectivity and enhances pain-related working memory deficits in neuropathic pain rats. Eur J Pain 2018; 22:1002-1015. [PMID: 29377353 DOI: 10.1002/ejp.1186] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/27/2017] [Indexed: 11/09/2022]
Abstract
BACKGROUND Dopamine (DA) is thought to be important to local hippocampal networks integrity during spatial working memory (sWM) processing. Chronic pain may contribute to deficient dopaminergic signalling, which may in turn affect cognition. However, the neural mechanisms that determine this impairment are poorly understood. Here, we evaluated whether the sWM impairment characteristic of animal models of chronic pain is dependent on DA D2 receptor (D2r) activity. METHODS To address this issue, we implanted multichannel arrays of electrodes in the dorsal and ventral hippocampal CA1 field (dvCA1) of rats and recorded the neuronal activity during a classical delayed food-reinforced T-maze sWM task. Within-subject behavioural performance and patterns of dorsoventral neural activity were assessed before and after the onset of persistent neuropathic pain using the spared nerve injury (SNI) model. RESULTS Our results show that the peripheral nerve lesion caused a disruption in sWM and hippocampus spike activity and that disruption was maximized by the systemic administration of the D2r antagonist raclopride. These deficits are strictly correlated with a selective disruption of hippocampal theta-oscillations. Particularly, we found a significant decrease in intrahippocampal CA1 field connectivity level. CONCLUSIONS Together, these results suggest that disruption of the dopaminergic balance in the intrahippocampal networks may be important for the development of cognitive deficits experienced during painful conditions. SIGNIFICANCE This study provides new insights into the role of D2r in the manifestation of pain-related sWM deficits. Our findings support that selective blockade of D2r produces a significant decrease in intrahippocampal connectivity mediated by theta-oscillations, and amplifies pain-related sWM deficits. These results suggest that further characterization of intrahippocampal dopaminergic modulation may be clinically relevant for the understanding of cognitive impairments that accompanies nociceptive stressful conditions.
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Affiliation(s)
- H Cardoso-Cruz
- Departamento de Biomedicina - Unidade de Biologia Experimental, Faculdade de Medicina, Centro de investigação Médica, Universidade do Porto, Porto, Portugal.,I3S - Instituto de Investigação e Inovação em Saúde & IBMC - Instituto de Biologia Molecular e Celular, Pain Research Group, Universidade do Porto, Porto, Portugal
| | - M Dourado
- Departamento de Biomedicina - Unidade de Biologia Experimental, Faculdade de Medicina, Centro de investigação Médica, Universidade do Porto, Porto, Portugal.,I3S - Instituto de Investigação e Inovação em Saúde & IBMC - Instituto de Biologia Molecular e Celular, Pain Research Group, Universidade do Porto, Porto, Portugal.,PDN - Programa Doutoral em Neurociências, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
| | - C Monteiro
- Departamento de Biomedicina - Unidade de Biologia Experimental, Faculdade de Medicina, Centro de investigação Médica, Universidade do Porto, Porto, Portugal.,I3S - Instituto de Investigação e Inovação em Saúde & IBMC - Instituto de Biologia Molecular e Celular, Pain Research Group, Universidade do Porto, Porto, Portugal
| | - V Galhardo
- Departamento de Biomedicina - Unidade de Biologia Experimental, Faculdade de Medicina, Centro de investigação Médica, Universidade do Porto, Porto, Portugal.,I3S - Instituto de Investigação e Inovação em Saúde & IBMC - Instituto de Biologia Molecular e Celular, Pain Research Group, Universidade do Porto, Porto, Portugal
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8
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Lazenka MF, Freitas KC, Henck S, Negus SS. Relief of Pain-Depressed Behavior in Rats by Activation of D1-Like Dopamine Receptors. J Pharmacol Exp Ther 2017; 362:14-23. [PMID: 28411257 DOI: 10.1124/jpet.117.240796] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 04/13/2017] [Indexed: 12/11/2022] Open
Abstract
Clinically significant pain often includes a decrease in both behavior and mesolimbic dopamine signaling. Indirect and/or direct dopamine receptor agonists may alleviate pain-related behavioral depression. To test this hypothesis, the present study compared effects of indirect and direct dopamine agonists in a preclinical assay of pain-depressed operant responding. Male Sprague-Dawley rats with chronic indwelling microelectrodes in the medial forebrain bundle were trained in an intracranial self-stimulation (ICSS) procedure to press a lever for pulses of electrical brain stimulation. Intraperitoneal injection of dilute lactic acid served as an acute noxious stimulus to depress ICSS. Intraperitoneal lactic acid-induced depression of ICSS was dose-dependently blocked by the dopamine transporter inhibitor methylphenidate and the D1-selective agonist SKF82958, but not by the D2/3-selective agonists quinpirole, pramipexole, or sumanirole. The antinociceptive effects of methylphenidate and SKF82958 were blocked by the D1-selective antagonist SCH39166. Acid-induced stimulation of a stretching response was evaluated in separate groups of rats, but all agonists decreased acid-stimulated stretching, and antagonism experiments were inconclusive due to direct effects of the antagonists when administered alone. Taken together, these results suggest that D1-receptor stimulation is both sufficient to block acid-induced depression of ICSS and necessary for methylphenidate antinociception in this procedure. Conversely, D2/3-receptor stimulation is not sufficient to relieve pain-depressed behavior. These results support the hypothesis that pain-related depression of dopamine D1 receptor signaling contributes to pain-related depression of behavior in rats. Additionally, these results support further consideration of indirect dopamine agonists and direct D1 receptor agonists as candidate treatments for pain-related behavioral depression.
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Affiliation(s)
- Matthew F Lazenka
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Kelen C Freitas
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - Sydney Henck
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
| | - S Stevens Negus
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
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