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Pontearso M, Slepicka J, Bhattacharyya A, Spicarova D, Palecek J. Dual effect of anandamide on spinal nociceptive transmission in control and inflammatory conditions. Biomed Pharmacother 2024; 173:116369. [PMID: 38452657 DOI: 10.1016/j.biopha.2024.116369] [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: 11/23/2023] [Revised: 02/26/2024] [Accepted: 02/28/2024] [Indexed: 03/09/2024] Open
Abstract
Anandamide (AEA) is an important modulator of nociception in the spinal dorsal horn, acting presynaptically through Cannabinoid (CB1) and Transient receptor potential vanilloid (TRPV1) receptors. The role of AEA (1 µM, 10 µM, and 30 µM) application on the modulation of nociceptive synaptic transmission under control and inflammatory conditions was studied by recording miniature excitatory postsynaptic currents (mEPSCs) from neurons in spinal cord slices. Inhibition of the CB1 receptors by PF514273, TRPV1 by SB366791, and the fatty acid amide hydrolase (FAAH) by URB597 was used. Under naïve conditions, the AEA application did not affect the mEPSCs frequency (1.43±0.12 Hz) when all the recorded neurons were considered. The mEPSC frequency increased (180.0±39.2%) only when AEA (30 µM) was applied with PF514273 and URB597. Analysis showed that one sub-population of neurons had synaptic input inhibited (39.1% of neurons), the second excited (43.5%), whereas 8.7% showed a mixed effect and 8.7% did not respond to the AEA. With inflammation, the AEA effect was highly inhibitory (72.7%), while the excitation was negligible (9.1%), and 18.2% were not modulated. After inflammation, more neurons (45.0%) responded even to low AEA by mEPSC frequency increase with PF514273/URB597 present. AEA-induced dual (excitatory/inhibitory) effects at the 1st nociceptive synapse should be considered when developing analgesics targeting the endocannabinoid system. These findings contrast the clear inhibitory effects of the AEA precursor 20:4-NAPE application described previously and suggest that modulation of endogenous AEA production may be more favorable for analgesic treatments.
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Affiliation(s)
- Monica Pontearso
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jakub Slepicka
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Anirban Bhattacharyya
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Diana Spicarova
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jiri Palecek
- Laboratory of Pain Research, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic.
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2
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Hoshijima H, Hunt M, Nagasaka H, Yaksh T. Systematic Review of Systemic and Neuraxial Effects of Acetaminophen in Preclinical Models of Nociceptive Processing. J Pain Res 2021; 14:3521-3552. [PMID: 34795520 PMCID: PMC8594782 DOI: 10.2147/jpr.s308028] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 09/11/2021] [Indexed: 12/29/2022] Open
Abstract
Acetaminophen (APAP) in humans has robust effects with a high therapeutic index in altering postoperative and inflammatory pain states in clinical and experimental pain paradigms with no known abuse potential. This review considers the literature reflecting the preclinical actions of acetaminophen in a variety of pain models. Significant observations arising from this review are as follows: 1) acetaminophen has little effect upon acute nociceptive thresholds; 2) acetaminophen robustly reduces facilitated states as generated by mechanical and thermal hyperalgesic end points in mouse and rat models of carrageenan and complete Freund’s adjuvant evoked inflammation; 3) an antihyperalgesic effect is observed in models of facilitated processing with minimal inflammation (eg, phase II intraplantar formalin); and 4) potent anti-hyperpathic effects on the thermal hyperalgesia, mechanical and cold allodynia, allodynic thresholds in rat and mouse models of polyneuropathy and mononeuropathies and bone cancer pain. These results reflect a surprisingly robust drug effect upon a variety of facilitated states that clearly translate into a wide range of efficacy in preclinical models and to important end points in human therapy. The specific systems upon which acetaminophen may act based on targeted delivery suggest both a spinal and a supraspinal action. Review of current targets for this molecule excludes a role of cyclooxygenase inhibitor but includes effects that may be mediated through metabolites acting on the TRPV1 channel, or by effect upon cannabinoid and serotonin signaling. These findings suggest that the mode of action of acetaminophen, a drug with a long therapeutic history of utilization, has surprisingly robust effects on a variety of pain states in clinical patients and in preclinical models with a good therapeutic index, but in spite of its extensive use, its mechanisms of action are yet poorly understood.
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Affiliation(s)
- Hiroshi Hoshijima
- Department of Anesthesiology, Saitama Medical University Hospital, Saitama, Japan
| | - Matthew Hunt
- Departments of Anesthesiology and Pharmacology, University of California, San Diego Anesthesia Research Laboratory, La Jolla, CA, USA
| | - Hiroshi Nagasaka
- Department of Anesthesiology, Saitama Medical University Hospital, Saitama, Japan
| | - Tony Yaksh
- Departments of Anesthesiology and Pharmacology, University of California, San Diego Anesthesia Research Laboratory, La Jolla, CA, USA
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3
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The Endocannabinoid/Endovanilloid System in Bone: From Osteoporosis to Osteosarcoma. Int J Mol Sci 2019; 20:ijms20081919. [PMID: 31003519 PMCID: PMC6514542 DOI: 10.3390/ijms20081919] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 04/16/2019] [Accepted: 04/17/2019] [Indexed: 12/20/2022] Open
Abstract
Bone is a dynamic tissue, whose homeostasis is maintained by a fine balance between osteoclast (OC) and osteoblast (OB) activity. The endocannabinoid/endovanilloid (EC/EV) system’s receptors are the cannabinoid receptor type 1 (CB1), the cannabinoid receptor type 2 (CB2), and the transient receptor potential cation channel subfamily V member 1 (TRPV1). Their stimulation modulates bone formation and bone resorption. Bone diseases are very common worldwide. Osteoporosis is the principal cause of bone loss and it can be caused by several factors such as postmenopausal estrogen decrease, glucocorticoid (GC) treatments, iron overload, and chemotherapies. Studies have demonstrated that CB1 and TRPV1 stimulation exerts osteoclastogenic effects, whereas CB2 stimulation has an anti-osteoclastogenic role. Moreover, the EC/EV system has been demonstrated to have a role in cancer, favoring apoptosis and inhibiting cell proliferation. In particular, in bone cancer, the modulation of the EC/EV system not only reduces cell growth and enhances apoptosis but it also reduces cell invasion and bone pain in mouse models. Therefore, EC/EV receptors may be a useful pharmacological target in the prevention and treatment of bone diseases. More studies to better investigate the biochemical mechanisms underlining the EC/EV system effects in bone are needed, but the synthesis of hybrid molecules, targeting these receptors and capable of oppositely regulating bone homeostasis, seems to be a promising and encouraging prospective in bone disease management.
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Wang Y, Lin W, Wu N, He X, Wang J, Feng Z, Xie XQ. An insight into paracetamol and its metabolites using molecular docking and molecular dynamics simulation. J Mol Model 2018; 24:243. [PMID: 30121710 PMCID: PMC6733030 DOI: 10.1007/s00894-018-3790-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 08/09/2018] [Indexed: 10/28/2022]
Abstract
Paracetamol is a relatively safe analgesia/antipyretic drug without the risks of addiction, dependence, tolerance, and withdrawal when used alone. However, when administrated in an opioid/paracetamol combination product, which often contains a large quantity of paracetamol, it can be potentially dangerous due to the risk of hepatotoxicity. Paracetamol is known to be metabolized into N-(4-hydroxyphenyl)-arachidonamide (AM404) via fatty acid amide hydrolase (FAAH) and into N-acetyl-p-benzoquinone imine (NAPQI) via cytochrome P450 (CYP) enzymes. However, the underlying mechanism of paracetamol is still unclear. In addition, paracetamol has the potential to interact with other drugs that are also involved with CYP family enzymes (inducer/inhibitor/substrate), an example being illicit drugs. In our present work, we looked into the relationship between paracetamol and its metabolites (AM404 and NAPQI) using molecular docking and molecular dynamics (MD) simulations. We first carried out a series of molecular docking studies between paracetamol/AM404/NAQPI and their reported targets, including CYP 2E1, FAAH, TRPA1, CB1, and TRPV1. Subsequently, we performed MD simulations and energy decomposition for CB1-AM404, TRPV1-AM404, and TRPV1-NAPQI for further investigation of the dynamics interactions. Finally, we summarized and discussed the reported drug-drug interactions between paracetamol and central nervous system drugs, especially illicit drugs. Overall, we are able to provide new insights into the structural and functional roles of paracetamol and its metabolites that can inform the potential prevention and treatment of paracetamol overdose. Graphical abstract Paracetamol and its metabolites.
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Affiliation(s)
- Yuanqiang Wang
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- School of Pharmacy and Bioengineering, Chongqing University of Technology, Chongqing, 400054, China
- Chongqing Key Laboratory of Medicinal Chemistry and Molecular Pharmacology, Chongqing, 400054, China
- Chongqing Key Laboratory of Target Based Drug Screening and Effect Evaluation, Chongqing, 400054, China
| | - Weiwei Lin
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Nan Wu
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Xibing He
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Junmei Wang
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Zhiwei Feng
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
| | - Xiang-Qun Xie
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
- National Center of Excellence for Computational Drug Abuse Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
- Drug Discovery Institute, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
- Departments of Computational Biology and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
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Pace MC, Passavanti MB, De Nardis L, Bosco F, Sansone P, Pota V, Barbarisi M, Palagiano A, Iannotti FA, Panza E, Aurilio C. Nociceptor plasticity: A closer look. J Cell Physiol 2017; 233:2824-2838. [PMID: 28488779 DOI: 10.1002/jcp.25993] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Revised: 04/20/2017] [Accepted: 05/09/2017] [Indexed: 12/17/2022]
Abstract
Nociceptors are receptors specifically involved in detecting a tissue damage and transducing it in an electrical signal. Nociceptor activation provoked by any kind of acute lesion is related to the release of several mediators of inflammation, within the framework of a process defined as "peripheral sensitization." This results in an exaggerated response to the painful stimulus, clinically defined as "primary hyperalgesia." The concept of "neuroplasticity" may explain the adaptive mechanisms carried out by the Nervous System in relation to a "harmful" damage; also, neuroplasticity mechanisms are also fundamental for rehabilitative intervention protocols. Here we review several studies that addressed the role of different receptors and ionic channels discovered on nociceptor surface and their role in pain perception. The changes in expression, distribution, and functioning of receptors and ionic channels are thought to be a part of the neuroplasticity property, through which the Nervous System constantly adapts to external stimuli. Moreover, some of the reviewed mediators are also been associated to "central sensitization," a process that results in pain chronicization when the painful stimulation is particularly prolonged or intense, and lastly leads to the memorization of the uncomfortable painful perception.
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Affiliation(s)
- Maria Caterina Pace
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Maria Beatrice Passavanti
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Lorenzo De Nardis
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Fabio Bosco
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Pasquale Sansone
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Vincenzo Pota
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Manlio Barbarisi
- Laboratory of Applied Biotechnology, Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
| | - Antonio Palagiano
- Department of Women, Child and General and Specialized Surgery, Second University of Naples, Naples, Italy
| | - Fabio Arturo Iannotti
- Institute of Biomolecular Chemistry (ICB) Research National Council (CNR), Pozzuoli, Italy
| | - Elisabetta Panza
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Caterina Aurilio
- Department of Anaesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy
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6
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Faraji N, Komaki A, Salehi I. Interaction Between the Cannabinoid and Vanilloid Systems on Anxiety in Male Rats. Basic Clin Neurosci 2017; 8:129-137. [PMID: 28539997 PMCID: PMC5440922 DOI: 10.18869/nirp.bcn.8.2.129] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Introduction: Previous studies have shown that the cannabinoid system is involved in anxiety. In addition, transient receptor potential vanilloid type-1 (TRPV1) channels are new targets for the development of anxiolytics. The present study investigated the possible interaction between the cannabinoid and vanilloid systems on anxiety-like behavior in rats. Methods: Four different groups of male Wistar rats received intraperitoneal (IP) injections of (1) vehicle (DMSO+saline), (2) cannabinoid receptor agonist WIN55212-2 (WIN) (1 mg/kg), (3) TRPV1 receptor antagonist capsazepine (CPZ) (5 mg/kg), or (4) combined WIN (1 mg/kg) and CPZ (5 mg/kg) treatment 30 minutes before testing in the elevated plus maze. Results: The results showed that compared to the control (vehicle), both WIN and CPZ increased the time spent and number of entries on the open arms. Co-administration of WIN and CPZ had a synergistic effect, i.e., the number of entries and time spent on the open arms was greater than that in the groups administered the two compounds alone. The total distance travelled by rats and total number of entries on to the arms did not significantly differ between groups. Conclusion: Acute neuropharmacological blockade of the TRPV1 receptor or stimulation of the CB1 receptor produced an anxiolytic effect. It seems that antagonism of the vanilloid system modulates cannabinoid gain that rises the anxiolytic effect. TRPV1 antagonism may amend generation of endocannabinoids, which in turn increases anxiolytic impact. These results suggest that two systems could act on or share a common signaling pathway affecting the expression of anxiety.
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Affiliation(s)
- Nafiseh Faraji
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.,Department of Biology, Hamadan Branch, Islamic Azad University, Hamadan, Iran
| | - Alireza Komaki
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Iraj Salehi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
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7
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Gervasi MG, Osycka-Salut C, Sanchez T, Alonso CAI, Llados C, Castellano L, Franchi AM, Villalón M, Perez-Martinez S. Sperm Release From the Oviductal Epithelium Depends on Ca(2+) Influx Upon Activation of CB1 and TRPV1 by Anandamide. J Cell Biochem 2016; 117:320-33. [PMID: 26129689 DOI: 10.1002/jcb.25273] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 06/24/2015] [Indexed: 01/01/2023]
Abstract
The oviduct acts as a functional sperm reservoir in many mammalian species. Both binding and release of spermatozoa from the oviductal epithelium are mainly modulated by sperm capacitation. Several molecules from oviductal fluid are involved in the regulation of sperm function. Anandamide is a lipid mediator involved in reproductive physiology. Previously, we demonstrated that anandamide, through activation of the cannabinoid receptor type 1 (CB1), promotes sperm release from bovine oviductal epithelial cells, and through CB1 and the transient receptor potential vanilloid 1 (TRPV1), induces sperm capacitation. Herein we investigate co-activation between CB1 and TRPV1, and Ca(2+) influx as part of the mechanism of action of anandamide during sperm release from oviductal cells. Our results indicate that in the absence of Ca(2+) anandamide failed to release spermatozoa from oviductal epithelial cells. Additionally, sperm release promoted by cannabinoid and vanilloid agonists was abolished when the spermatozoa were preloaded with BAPTA-AM, a Ca(2+) chelator. We also determined Ca(2+) levels in spermatozoa preloaded with FURA2-AM co-cultured with oviductal cells and incubated with different cannabinoid and vanilloid agonists. The incubation with different agonists induced Ca(2+) influx, which was abolished by CB1 or TRPV1 antagonists. Our results also suggest that a phospholypase C (PLC) might mediate the activation of CB1 and TRPV1 in sperm release from the bovine oviduct. Therefore, our findings indicate that anandamide, through CB1 and TRPV1 activation, is involved in sperm release from the oviductal reservoir. An increase of sperm Ca(2+) levels and the PLC activation might be involved in anandamide signaling pathway.
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Affiliation(s)
- M G Gervasi
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts.,Laboratorio de Biología de la Reproducción en Mamíferos, Centro de Estudios Farmacológicos y Botánicos, (CONICET-UBA), Buenos Aires-Argentina
| | - C Osycka-Salut
- Laboratorio de Biología de la Reproducción en Mamíferos, Centro de Estudios Farmacológicos y Botánicos, (CONICET-UBA), Buenos Aires-Argentina
| | - T Sanchez
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - C A I Alonso
- Laboratorio de Biología de la Reproducción en Mamíferos, Centro de Estudios Farmacológicos y Botánicos, (CONICET-UBA), Buenos Aires-Argentina
| | - C Llados
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - L Castellano
- Laboratorio de Biología de la Reproducción en Mamíferos, Centro de Estudios Farmacológicos y Botánicos, (CONICET-UBA), Buenos Aires-Argentina
| | - A M Franchi
- Laboratorio de Fisiopatología de la Preñez y el Parto, Centro de Estudios Farmacológicos y Botánicos (CONICET-UBA), Buenos Aires-Argentina
| | - M Villalón
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - S Perez-Martinez
- Laboratorio de Biología de la Reproducción en Mamíferos, Centro de Estudios Farmacológicos y Botánicos, (CONICET-UBA), Buenos Aires-Argentina
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8
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Chen J, Varga A, Selvarajah S, Jenes A, Dienes B, Sousa-Valente J, Kulik A, Veress G, Brain SD, Baker D, Urban L, Mackie K, Nagy I. Spatial Distribution of the Cannabinoid Type 1 and Capsaicin Receptors May Contribute to the Complexity of Their Crosstalk. Sci Rep 2016; 6:33307. [PMID: 27653550 PMCID: PMC5032030 DOI: 10.1038/srep33307] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/24/2016] [Indexed: 01/07/2023] Open
Abstract
The cannabinoid type 1 (CB1) receptor and the capsaicin receptor (TRPV1) exhibit co-expression and complex, but largely unknown, functional interactions in a sub-population of primary sensory neurons (PSN). We report that PSN co-expressing CB1 receptor and TRPV1 form two distinct sub-populations based on their pharmacological properties, which could be due to the distribution pattern of the two receptors. Pharmacologically, neurons respond either only to capsaicin (COR neurons) or to both capsaicin and the endogenous TRPV1 and CB1 receptor ligand anandamide (ACR neurons). Blocking or deleting the CB1 receptor only reduces both anandamide- and capsaicin-evoked responses in ACR neurons. Deleting the CB1 receptor also reduces the proportion of ACR neurons without any effect on the overall number of capsaicin-responding cells. Regarding the distribution pattern of the two receptors, neurons express CB1 and TRPV1 receptors either isolated in low densities or in close proximity with medium/high densities. We suggest that spatial distribution of the CB1 receptor and TRPV1 contributes to the complexity of their functional interaction.
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Affiliation(s)
- Jie Chen
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK.,Department of Anaesthesiology, Southwest Hospital, Third Military Medical University, Gaotanyan 19 Street, Shapingba, Chongqing 400038, P. R. China
| | - Angelika Varga
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK.,MTA-DE-NAP B-Pain Control Research GroupDepartment of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, H-4012, Hungary
| | - Srikumaran Selvarajah
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK
| | - Agnes Jenes
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK.,MTA-DE-NAP B-Pain Control Research GroupDepartment of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, H-4012, Hungary
| | - Beatrix Dienes
- MTA-DE-NAP B-Pain Control Research GroupDepartment of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, H-4012, Hungary
| | - Joao Sousa-Valente
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK
| | - Akos Kulik
- Institute of Physiology, University of Freiburg, Germany D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signalling Studies, University of Freiburg, D-79104, Germany
| | - Gabor Veress
- Department of Laboratory Medicine, Faculty of Medicine and Health, Örebro University, Örebro, Sweden
| | - Susan D Brain
- BHF Cardiovascular Centre of Excellence and Centre of Integrative Biomedicine, Cardiovascular Division, King's College London, London SE1 9NH, UK
| | - David Baker
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London, E1 2AT, UK
| | - Laszlo Urban
- Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institutes for Biommedical Research, Cambridge, MA 01932, USA
| | - Ken Mackie
- Department of Psychological and Brain Sciences and Program in Neuroscience, Indiana University, The Gill Center, 702 N. Walnut Grove Avenue, Bloomington, IN 47405, USA
| | - Istvan Nagy
- Section of Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London, SW10 9NH, UK
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9
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Tahmasebi L, Komaki A, Karamian R, Shahidi S, Sarihi A, Salehi I, Nikkhah A. The interactive role of cannabinoid and vanilloid systems in hippocampal synaptic plasticity in rats. Eur J Pharmacol 2015; 757:68-73. [PMID: 25843413 DOI: 10.1016/j.ejphar.2015.03.063] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 03/23/2015] [Accepted: 03/25/2015] [Indexed: 01/12/2023]
Abstract
Long-term potentiation (LTP) has been most thoroughly studied in the hippocampus, which has a key role in learning and memory. Endocannabinoids are one of the endogenous systems that modulate this kind of synaptic plasticity. The activation of the vanillioid system has also been shown to mediate synaptic plasticity in the hippocampus. In addition, immunohistochemical studies have shown that cannabinoid receptor type 1 (CB1) and vanilloid receptor 1 (TRPV1) are closely located in the hippocampus. In this study, we examined the hippocampal effects of co-administrating WIN55-212-2 and capsaicin, which are CB1 and TRPV1 agonists, respectively, on the induction of LTP in the dentate gyrus (DG) of rats. LTP in the hippocampal area was induced by high-frequency stimulation (HFS). Our results indicated that the cannabinoid agonist reduced both field excitatory post-synaptic potential (fEPSP) slope and population spike (PS) amplitude after HFS with respect to the control group, whereas the vanilloid agonist increased these parameters along with the increased induction of LTP as compared to the control group. We also showed that the co-administration of cannabinoid and vanilloid agonists had different effects on fEPSP slope and PS amplitude. It seems that agonists of the vanilloid system modulate cannabinoid outputs that cause an increase in synaptic plastisity, while in contemporary consumption of two agonist, TRPV1 agonist can change production of endocannabinoid, which in turn result to enhancement of LTP induction. These findings suggest that the two systems may interact or share certain common signaling pathways in the hippocampus.
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Affiliation(s)
- Lida Tahmasebi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Alireza Komaki
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
| | - Ruhollah Karamian
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Siamak Shahidi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Abdolrahman Sarihi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Iraj Salehi
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Ali Nikkhah
- Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
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10
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You Y, Ren T, Zhang S, Shirima GG, Cheng Y, Liu X. Hypoglycemic effects of Zanthoxylum alkylamides by enhancing glucose metabolism and ameliorating pancreatic dysfunction in streptozotocin-induced diabetic rats. Food Funct 2015. [DOI: 10.1039/c5fo00432b] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alkylamides extracted from Zanthoxylum, a seasoning spice and folk medicine, exhibited hypoglycemic properties by enhancing glucose metabolism and ameliorating pancreatic dysfunction.
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Affiliation(s)
- Yuming You
- College of Food Science
- Southwest University
- Chongqing
- China
- College of Forestry and Life Science
| | - Ting Ren
- College of Food Science
- Southwest University
- Chongqing
- China
| | - Shiqi Zhang
- College of Food Science
- Southwest University
- Chongqing
- China
| | | | - YaJiao Cheng
- College of Food Science
- Southwest University
- Chongqing
- China
| | - Xiong Liu
- College of Food Science
- Southwest University
- Chongqing
- China
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11
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Devesa I, Ferrer-Montiel A. Neurotrophins, endocannabinoids and thermo-transient receptor potential: a threesome in pain signalling. Eur J Neurosci 2014; 39:353-62. [PMID: 24494676 DOI: 10.1111/ejn.12455] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/10/2013] [Accepted: 11/15/2013] [Indexed: 01/11/2023]
Abstract
Because of the social and economic costs of chronic pain, there is a growing interest in unveiling the cellular and molecular mechanisms underlying it with the aim of developing more effective medications. Pain signalling is a multicomponent process that involves the peripheral and central nervous systems. At the periphery, nociceptor sensitisation by pro-inflammatory mediators is a primary step in pain transduction. Although pain is multifactorial at cellular and molecular levels, it is widely accepted that neurotrophin (TrkA, p75NTR, Ret and GFRs), cannabinoid (CB1 and CB2), and thermo-transient receptor potential (TRPs; TRPV1, TRPA1 and TRPM8) receptors play a pivotal role. They form a threesome for which endocannabinoids appear to be a first line of defence against pain, while neurotrophins and thermoTRPs are the major generators of painful signals. However, endocannabinoids may exhibit nociceptive activity while some neurotrophins may display anti-nociception. Accordingly, a clear-cut knowledge of the modulation and context-dependent function of these signalling cascades, along with the molecular and dynamic details of their crosstalk, is critical for understanding and controlling pain transduction. Here, the recent progress in this fascinating topic, as well as the tantalizing questions that remain unanswered, will be discussed. Furthermore, we will underline the need for using a systems biology approach (referred to as systems pain) to uncover the dynamics and interplay of these intricate signalling cascades, taking into consideration the molecular complexity and cellular heterogeneity of nociceptor populations. Nonetheless, the available information confirms that pharmacological modulation of this signalling triad is a highly valuable therapeutic strategy for effectively treating pain syndromes.
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Affiliation(s)
- Isabel Devesa
- Instituto de Biología Molecular y Celular, Universitas Miguel Hernández, Av de la Universidad, 03202, Elche, Alicante, Spain
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12
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Mohammadi-Farani A, Ghazi-Khansari M, Sahebgharani M. Glucose concentration in culture medium affects mRNA expression of TRPV1 and CB1 receptors and changes capsaicin toxicity in PC12 cells. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2014; 17:673-378. [PMID: 25691944 PMCID: PMC4322151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 02/17/2014] [Indexed: 11/29/2022]
Abstract
OBJECTIVE S Hyperglycemia is widely recognized as the underlying cause for some debilitating conditions in diabetic patients. The role of cannabinoid CB1 and vanilloid TRPV1 receptors and their endogenous agonists, endovanilloids, in diabetic neuropathy is shown in many studies. Here we have used PC12 cell line to investigate the possible influence of glucose concentration in culture medium on cytoprotective or toxic effects of a CB1 [WIN55 212-2 (WIN)], or TRPV1 [Capsaicin (CAS)] agonist. MATERIALS AND METHODS Cell viability was tested using the MTT assay. We have also measured TRPV1 and CB1 transcripts by real time reverse transcription-polymerase chain reaction while cells were grown in low (5.5 mM) and high (50 mM) glucose concentrations. RESULTS Real time PCR results indicated that high glucose medium increased (P<0.01) TRPV1 mRNA and decreased (P <0.001) that of CB1. Cell culture tests show that hyperglycemic cells are more vulnerable (Dose × Medium, F (3,63)=41.5, P<0.001) to the toxic effects of capsaicin compared to those grown in low glucose medium. CONCLUSION These findings propose that hyperglycemic conditions may result in neuronal cell death because of inducing a counterbalance between cytotoxic TRPV1 and cytoprotective CB1 receptors.
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Affiliation(s)
- Ahmad Mohammadi-Farani
- Novel Drug Delivery Research Center, Faculty of Pharmacy, Kermanshah University of Medical Sciences, Kermanshah, Iran,Corresponding author: Ahmad Mohammadi-Farani. Faculty of Pharmacy, Parastar Boulevard, Daneshgah St, Kermanshah, Iran. ;
| | - Mahmoud Ghazi-Khansari
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mousa Sahebgharani
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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13
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Fawley JA, Hofmann ME, Andresen MC. Cannabinoid 1 and transient receptor potential vanilloid 1 receptors discretely modulate evoked glutamate separately from spontaneous glutamate transmission. J Neurosci 2014; 34:8324-32. [PMID: 24920635 PMCID: PMC4051980 DOI: 10.1523/jneurosci.0315-14.2014] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 05/07/2014] [Accepted: 05/09/2014] [Indexed: 11/21/2022] Open
Abstract
Action potentials trigger synaptic terminals to synchronously release vesicles, but some vesicles release spontaneously. G-protein-coupled receptors (GPCRs) can modulate both of these processes. At cranial primary afferent terminals, the GPCR cannabinoid 1 (CB1) is often coexpressed with transient receptor potential vanilloid 1 (TRPV1), a nonselective cation channel present on most afferents. Here we tested whether CB1 activation modulates synchronous, action potential-evoked (eEPSCs) and/or spontaneous (sEPSCs) EPSCs at solitary tract nucleus neurons. In rat horizontal brainstem slices, activation of solitary tract (ST) primary afferents generated ST-eEPSCs that were rapidly and reversibly inhibited from most afferents by activation of CB1 with arachidonyl-2'-chloroethylamide (ACEA) or WIN 55,212-2 [R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone monomethanesulfonate]. The CB1 antagonist/inverse agonist AM251 [N-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide] blocked these responses. Despite profound depression of ST-eEPSCs during CB1 activation, sEPSCs in these same neurons were unaltered. Changes in temperature changed sEPSC frequency only from TRPV1(+) afferents (i.e., thermal sEPSC responses only occurred in TRPV1(+) afferents). CB1 activation failed to alter these thermal sEPSC responses. However, the endogenous arachidonate metabolite N-arachidonyldopamine (NADA) promiscuously activated both CB1 and TRPV1 receptors. NADA inhibited ST-eEPSCs while simultaneously increasing sEPSC frequency, and thermally triggered sEPSC increases in neurons with TRPV1(+) afferents. We found no evidence for CB1/TRPV1 interactions suggesting independent regulation of two separate vesicle pools. Together, these data demonstrate that action potential-evoked synchronous glutamate release is modulated separately from TRPV1-mediated glutamate release despite coexistence in the same central terminations. This two-pool arrangement allows independent and opposite modulation of glutamate release by single lipid metabolites.
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Affiliation(s)
- Jessica A Fawley
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon 97239
| | - Mackenzie E Hofmann
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon 97239
| | - Michael C Andresen
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon 97239
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14
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Harkany T, Zeilhofer HU, Cattaneo A. Neurotrophin and endocannabinoid interactions in the neurobiology of pain. Eur J Neurosci 2014; 39:331-3. [PMID: 24494673 DOI: 10.1111/ejn.12483] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tibor Harkany
- Division of Molecular Neurobiology, Department of Medical Biochemistry & Biophysics, Karolinska Institutet, Stockholm, Sweden; Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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15
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Keimpema E, Hökfelt T, Harkany T, Doherty P. The molecular interplay between endocannabinoid and neurotrophin signals in the nervous system and beyond. Eur J Neurosci 2014; 39:334-43. [DOI: 10.1111/ejn.12431] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 10/16/2013] [Accepted: 10/18/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Erik Keimpema
- Division of Molecular Neurobiology; Department of Medical Biochemistry and Biophysics; Karolinska Institutet; Scheeles väg 1:A1 SE-17177 Stockholm Sweden
- Department of Molecular Neuroscience; Center for Brain Research; Medical University of Vienna; Spitalgasse 4 A-1090 Vienna Austria
| | - Tomas Hökfelt
- Department of Neuroscience; Karolinska Institutet; Stockholm Sweden
| | - Tibor Harkany
- Division of Molecular Neurobiology; Department of Medical Biochemistry and Biophysics; Karolinska Institutet; Scheeles väg 1:A1 SE-17177 Stockholm Sweden
- Department of Molecular Neuroscience; Center for Brain Research; Medical University of Vienna; Spitalgasse 4 A-1090 Vienna Austria
| | - Patrick Doherty
- Wolfson Centre for Age-Related Diseases; King's College London; London SE1 9RT UK
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16
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Luongo L, Maione S, Di Marzo V. Endocannabinoids and neuropathic pain: focus on neuron-glia and endocannabinoid-neurotrophin interactions. Eur J Neurosci 2014; 39:401-8. [DOI: 10.1111/ejn.12440] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/31/2013] [Accepted: 11/04/2013] [Indexed: 12/16/2022]
Affiliation(s)
- Livio Luongo
- Department of Experimental Medicine; Division of Pharmacology ‘L. Donatelli’; Second University of Naples; Naples Italy
| | - Sabatino Maione
- Department of Experimental Medicine; Division of Pharmacology ‘L. Donatelli’; Second University of Naples; Naples Italy
| | - Vincenzo Di Marzo
- Institute of Biomolecular Chemistry; Consiglio Nazionale delle Ricerche; Via Campi Flegrei 34 80078 Pozzuoli (NA) Italy
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17
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Tender GC, Li YY, Cui JG. The role of nerve growth factor in neuropathic pain inhibition produced by resiniferatoxin treatment in the dorsal root ganglia. Neurosurgery 2014; 73:158-65; discussion 165-6. [PMID: 23615109 DOI: 10.1227/01.neu.0000429850.37449.c8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Resiniferatoxin (RTX), an excitotoxic agonist for vanilloid receptor 1, is a promising candidate for intractable pain treatment. OBJECTIVE We evaluated the effects of RTX, applied to dorsal root ganglia (DRG) at high doses (1200 ng), in sensory-motor function and nerve growth factor (NGF) alterations in a photochemical sciatic nerve injury rat model. METHODS Following RTX injection into the L3-6 DRG at high doses and behavioral evaluation, the rats were sacrificed and the DRG were tested by immunohistochemistry and mRNA analysis for NGF and its' receptors, tyrosine kinase A (TrkA) and p75. The correlation between neuropathic pain and NGF, TrkA, and p75 expression was analyzed. RESULTS The treated rats had preserved touch, cold, pain, and high-heat sensations, and exhibited hypoalgesia to low-heat stimulation. After RTX treatment, TrkA and p75 altered their expressions from one neuronal type to another in the DRG. NGF and p75 expression changed from the small-size neurons in neuropathic rat DRG to the large- and medium-size neurons in non-neuropathic and RTX-treated animals, concomitantly with neuropathic pain suppression. TrkA was expressed in the small-size neurons in neuropathic rat DRG, and was drastically reduced in all size neurons after RTX treatment. NGF, TrkA, and p75 mRNA expression supported these phenotypic changes in the DRG. CONCLUSION The pathway of NGF-TrkA expressed in the small-size neurons, associated with neuropathic pain, was shifted to the NGF-p75 pathway expressed in the large-size neurons after RTX treatment, in association with neuropathic pain inhibition. These findings may play an important role in clinical trial designs.
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Affiliation(s)
- Gabriel C Tender
- Department of Neurosurgery, Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
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18
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Frias B, Lopes T, Pinto R, Cruz F, Cruz CD. Neurotrophins in the lower urinary tract: becoming of age. Curr Neuropharmacol 2012; 9:553-8. [PMID: 22654715 PMCID: PMC3263451 DOI: 10.2174/157015911798376253] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 07/19/2010] [Accepted: 07/19/2010] [Indexed: 01/23/2023] Open
Abstract
The lower urinary tract (LUT) comprises a storage unit, the urinary bladder, and an outlet, the urethra. The coordination between the two structures is tightly controlled by the nervous system and, therefore, LUT function is highly susceptible to injuries to the neuronal pathways involved in micturition control. These injuries may include lesions to the
spinal cord or to nerve fibres and result in micturition dysfunction. A common trait of micturition pathologies, irrespective of its origin, is an upregulation in synthesis and secretion of neurotrophins, most notably Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF). These neurotrophins are produced by neuronal and non-neuronal cells and exert their effects upon binding to their high-affinity receptors abundantly expressed in the neuronal circuits regulating
LUT function. In addition, NGF and BDNF are present in detectable amounts in the urine of patients suffering from various LUT pathologies, suggesting that analysis of urinary NGF and BDNF may serve as likely biomarkers to be studied in tandem with other factors when diagnosing patients. Studies with experimental models of bladder dysfunction
using antagonists of NGF and BDNF receptors as well as scavenging agents suggest that those NTs may be key elements in the pathophysiology of bladder dysfunctions. In addition, available data indicates that NGF and BDNF might constitute future targets for designing new drugs for better treatment of bladder dysfunction.
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Affiliation(s)
- Bárbara Frias
- Department of Experimental Biology, Faculty of Medicine of Porto, Alameda Hernâni Monteiro, 4200-319 Porto, Portugal
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19
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Tsumura M, Sobhan U, Muramatsu T, Sato M, Ichikawa H, Sahara Y, Tazaki M, Shibukawa Y. TRPV1-mediated calcium signal couples with cannabinoid receptors and sodium-calcium exchangers in rat odontoblasts. Cell Calcium 2012; 52:124-36. [PMID: 22656960 DOI: 10.1016/j.ceca.2012.05.002] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 04/24/2012] [Accepted: 05/02/2012] [Indexed: 11/30/2022]
Abstract
Odontoblasts are involved in the transduction of stimuli applied to exposed dentin. Although expression of thermo/mechano/osmo-sensitive transient receptor potential (TRP) channels has been demonstrated, the properties of TRP vanilloid 1 (TRPV1)-mediated signaling remain to be clarified. We investigated physiological and pharmacological properties of TRPV1 and its functional coupling with cannabinoid (CB) receptors and Na(+)-Ca(2+) exchangers (NCXs) in odontoblasts. Anandamide (AEA), capsaicin (CAP), resiniferatoxin (RF) or low-pH evoked Ca(2+) influx. This influx was inhibited by capsazepine (CPZ). Delay in time-to-activation of TRPV1 channels was observed between application of AEA or CAP and increase in [Ca(2+)](i). In the absence of extracellular Ca(2+), however, an immediate increase in [Ca(2+)](i) was observed on administration of extracellular Ca(2+), followed by activation of TRPV1 channels. Intracellular application of CAP elicited inward current via opening of TRPV1 channels faster than extracellular application. With extracellular RF application, no time delay was observed in either increase in [Ca(2+)](i) or inward current, indicating that agonist binding sites are located on both extra- and intracellular domains. KB-R7943, an NCX inhibitor, yielded an increase in the decay time constant during TRPV1-mediated Ca(2+) entry. Increase in [Ca(2+)](i) by CB receptor agonist, 2-arachidonylglycerol, was inhibited by CB1 receptor antagonist or CPZ, as well as by adenylyl cyclase inhibitor. These results showed that TRPV1-mediated Ca(2+) entry functionally couples with CB1 receptor activation via cAMP signaling. Increased [Ca(2+)](i) by TRPV1 activation was extruded by NCXs. Taken together, this suggests that cAMP-mediated CB1-TRPV1 crosstalk and TRPV1-NCX coupling play an important role in driving cellular functions following transduction of external stimuli to odontoblasts.
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Affiliation(s)
- Maki Tsumura
- Oral Health Science Center hrc8, Tokyo Dental College, Chiba, Japan
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20
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Liao HT, Lee HJ, Ho YC, Chiou LC. Capsaicin in the periaqueductal gray induces analgesia via metabotropic glutamate receptor-mediated endocannabinoid retrograde disinhibition. Br J Pharmacol 2011; 163:330-45. [PMID: 21232043 DOI: 10.1111/j.1476-5381.2011.01214.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Capsaicin, an agonist of transient receptor potential vanilloid 1 (TRPV1) channels, is pro-nociceptive in the periphery but is anti-nociceptive when administered into the ventrolateral periaqueductal gray (vlPAG), a midbrain region for initiating descending pain inhibition. Here, we investigated how activation of TRPV1 channels in the vlPAG leads to anti-nociception. EXPERIMENTAL APPROACH We examined synaptic transmission and neuronal activity using whole-cell recordings in vlPAG slices in vitro and hot-plate nociceptive responses in rats after drug microinjection into the vlPAG in vivo. KEY RESULTS Capsaicin (1-10 µM) depressed evoked GABAergic inhibitory postsynaptic currents (eIPSCs) in vlPAG slices presynaptically, while increasing miniature excitatory PSC frequency. Capsaicin-induced eIPSC depression was antagonized by cannabinoid CB₁ and metabotropic glutamate (mGlu₅) receptor antagonists, and prevented by inhibiting diacylglycerol lipase (DAGL), which converts DAG into 2-arachidonoylglycerol (2-AG), an endocannabinoid. Capsaicin induced membrane depolarization in 2/3 neurons recorded but, overall, increased neuronal firings by increasing evoked postsynaptic potentials. Intra-vlPAG capsaicin reduced hot-plate responses in rats, effects blocked by CB₁ and mGlu receptor antagonists. Effects of capsaicin were antagonized by SB 366791, a TRPV1 channel antagonist. CONCLUSIONS AND IMPLICATIONS Capsaicin activated TRPV1s on glutamatergic terminals to release glutamate which activated postsynaptic mGlu₅ receptors, yielding 2-AG from DAG by DAGL hydrolysis. 2-AG induces retrograde inhibition (disinhibition) of GABA release via presynaptic CB₁ receptors. This disinhibition in the vlPAG leads to anti-nociception by activating the descending pain inhibitory pathway. This is a novel TRPV1 channel-mediated anti-nociceptive mechanism in the brain and a new interaction between vanilloid and endocannabinoid systems.
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Affiliation(s)
- H-T Liao
- Graduate Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
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The cannabinergic system is implicated in the upregulation of central NGF protein by psychotropic drugs. Psychopharmacology (Berl) 2011; 215:129-41. [PMID: 21170518 DOI: 10.1007/s00213-010-2120-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Accepted: 11/26/2010] [Indexed: 02/06/2023]
Abstract
RATIONALE Studies on the regulation of nerve growth factor (NGF) levels by psychotropics are limited in scope and the mechanism(s) remain elusive which merit further elucidation. OBJECTIVES We aimed to perform a more comprehensive investigation on the possible effects of pharmacologically heterogeneous groups of psychotropic drugs on NGF contents in the brain regions involved in the modulation of emotions. As a mechanistic approach, we looked at the role of the cannabinergic system which is linked to depression and/or antidepressant effect and appears to interact with neurotrophin signaling. METHODS Following psychotropic treatment, NGF or endocannabinoid (eCB) contents were quantified by Bio-Rad protein assay and isotope-dilution liquid chromatography/mass spectrometry, respectively. In case of any significant change, the effects of pretreatment with the CB(1) receptor neutral antagonist AM4113 were investigated. RESULTS Single injection of nortriptyline, isocarboxazid, citalopram, diazepam, risperidone (2.5, 5, and 10 mg/kg, each), and fluphenazine (0.25, 0.5, and 1 mg/kg) into rats did not alter NGF or eCB contents. Following 4-week treatment, all drugs except diazepam elevated NGF or eCB levels in dose-dependent and brain region-specific fashion. Pretreatment with the highest dose of AM4113 (5.6 mg/kg) prevented psychotropic-induced NGF or eCB elevation. AM4113 had no effect by itself. CONCLUSIONS The cannabinergic system is implicated in the mechanisms of action of certain psychotropic drugs including the upregulation of brain NGF levels. This provides a better understanding of the pathophysiological mechanisms underlying neuropsychiatric disorders, leading to novel drug design.
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Abstract
Since the first endocannabinoid anandamide was identified in 1992, extensive research has been conducted to characterize the elements of the tightly controlled endocannabinoid signaling system. While it was established that the activity of endocannabinoids are terminated by a two-step process that includes cellular uptake and degradation, there is still a continuing debate about the mechanistic role of these processes in inactivating anandamide signals.
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Jara-Oseguera A, Simon SA, Rosenbaum T. TRPV1: on the road to pain relief. Curr Mol Pharmacol 2010; 1:255-69. [PMID: 20021438 DOI: 10.2174/1874467210801030255] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Historically, drug research targeted to pain treatment has focused on trying to prevent the propagation of action potentials in the periphery from reaching the brain rather than pinpointing the molecular basis underlying the initial detection of the nociceptive stimulus: the receptor itself. This has now changed, given that many receptors of nociceptive stimuli have been identified and/or cloned. Transient Receptor Potential (TRP) channels have been implicated in several physiological processes such as mechanical, chemical and thermal stimuli detection. Ten years after the cloning of TRPV1, compelling data has been gathered on the role of this channel in inflammatory and neuropathic states. TRPV1 activation in nociceptive neurons, where it is normally expressed, triggers the release of neuropeptides and transmitters resulting in the generation of action potentials that will be sent to higher CNS areas where they will often be perceived as pain. Its activation also will evoke the peripheral release of pro-inflammatory compounds that may sensitize other neurons to physical, thermal or chemical stimuli. For these reasons as well as because its continuous activation causes analgesia, TRPV1 has become a viable drug target for clinical use in the management of pain. This review will provide a general picture of the physiological and pathophysiological roles of the TRPV1 channel and of its structural, pharmacological and biophysical properties. Finally, it will provide the reader with an overall view of the status of the discovery of potential therapeutic agents for the management of chronic and neuropathic pain.
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Affiliation(s)
- Andrés Jara-Oseguera
- Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
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Izzo AA, Sharkey KA. Cannabinoids and the gut: new developments and emerging concepts. Pharmacol Ther 2010; 126:21-38. [PMID: 20117132 DOI: 10.1016/j.pharmthera.2009.12.005] [Citation(s) in RCA: 301] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 12/24/2009] [Indexed: 12/11/2022]
Abstract
Cannabis has been used to treat gastrointestinal (GI) conditions that range from enteric infections and inflammatory conditions to disorders of motility, emesis and abdominal pain. The mechanistic basis of these treatments emerged after the discovery of Delta(9)-tetrahydrocannabinol as the major constituent of Cannabis. Further progress was made when the receptors for Delta(9)-tetrahydrocannabinol were identified as part of an endocannabinoid system, that consists of specific cannabinoid receptors, endogenous ligands and their biosynthetic and degradative enzymes. Anatomical, physiological and pharmacological studies have shown that the endocannabinoid system is widely distributed throughout the gut, with regional variation and organ-specific actions. It is involved in the regulation of food intake, nausea and emesis, gastric secretion and gastroprotection, GI motility, ion transport, visceral sensation, intestinal inflammation and cell proliferation in the gut. Cellular targets have been defined that include the enteric nervous system, epithelial and immune cells. Molecular targets of the endocannabinoid system include, in addition to the cannabinoid receptors, transient receptor potential vanilloid 1 receptors, peroxisome proliferator-activated receptor alpha receptors and the orphan G-protein coupled receptors, GPR55 and GPR119. Pharmacological agents that act on these targets have been shown in preclinical models to have therapeutic potential. Here, we discuss cannabinoid receptors and their localization in the gut, the proteins involved in endocannabinoid synthesis and degradation and the presence of endocannabinoids in the gut in health and disease. We focus on the pharmacological actions of cannabinoids in relation to GI disorders, highlighting recent data on genetic mutations in the endocannabinoid system in GI disease.
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Affiliation(s)
- Angelo A Izzo
- Department of Experimental Pharmacology, University of Naples Federico II and Endocannabinoid Research Group, Naples, Italy.
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25
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Appendino G, Ligresti A, Minassi A, Cascio MG, Allarà M, Taglialatela-Scafati O, Pertwee RG, De Petrocellis L, Di Marzo V. Conformationally constrained fatty acid ethanolamides as cannabinoid and vanilloid receptor probes. J Med Chem 2009; 52:3001-9. [PMID: 19361197 DOI: 10.1021/jm900130m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To investigate if certain acylethanolamides bind to both cannabinoid (CB(1) and CB(2)) and vanilloid TRPV1 receptors because of their conformational flexibility, we introduced a methylene lock on their ethanolamine "head", thereby generating a cyclopropane ring with two stereogenic centers and chiral cis/trans diastereomers with different topology of presentation to binding sites. After resolution by chiral-phase HPLC, diastereo- and enantiopure arachidonoyl-, oleoyl-, and palmitoylcyclopropanolamides were tested in assays of CB(1), CB(2), and TRPV1 activity. Diastereodifferentiation between pairs of cis-trans isomers was observed only for TRPV1 activity, with poor enantiodifferentiation. Methylenation introduced (i) CB(1) receptor affinity in oleoylethanolamide while increasing in a diastereoselective way its activity at TRPV1 and (ii) strong diastereoselective activity at TRPV1, but not cannabinoid, receptors in the otherwise inactive palmitoylethanolamide. These results show that the N-alkyl group of acylethanolamides has a different role in their interaction with cannabinoid and vanilloid receptors and that acylcyclopropanolamides qualify as CB(1)/TRPV1 "hybrids" of potential therapeutic utility.
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Affiliation(s)
- Giovanni Appendino
- Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, Università del Piemonte Orientale, Novara, Italy.
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26
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Role of endocannabinoids and endovanilloids in Ca2+ signalling. Cell Calcium 2009; 45:611-24. [DOI: 10.1016/j.ceca.2009.03.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 03/03/2009] [Accepted: 03/11/2009] [Indexed: 12/14/2022]
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Winkler M, Moraux T, Khairy HA, Scott RH, Slawin AMZ, O'Hagan D. Synthesis and Vanilloid Receptor (TRPV1) Activity of the Enantiomers of α-Fluorinated Capsaicin. Chembiochem 2009; 10:823-8. [DOI: 10.1002/cbic.200800709] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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28
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Rossi F, Siniscalco D, Luongo L, De Petrocellis L, Bellini G, Petrosino S, Torella M, Santoro C, Nobili B, Perrotta S, Di Marzo V, Maione S. The endovanilloid/endocannabinoid system in human osteoclasts: possible involvement in bone formation and resorption. Bone 2009; 44:476-84. [PMID: 19059369 DOI: 10.1016/j.bone.2008.10.056] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Revised: 10/18/2008] [Accepted: 10/26/2008] [Indexed: 01/05/2023]
Abstract
Recent studies suggest a role for the endocannabinoid/endovanilloid anandamide in the regulation of bone resorption/formation balance in mice. Here, we examined the co-expression of the transient receptor potential vanilloid type 1 (TRPV1) and the cannabinoid CB1/CB2 receptors together with N-acylphosphatidylethanolamine-hydrolizing phospholipase D (NAPE-PLD) and fatty acid amide hydrolase (FAAH), the two enzymes responsible of the synthesis and catabolism of anandamide respectively, in human osteoclasts. Co-expression of TRPV1, CB1/CB2, NAPE-PLD and FAAH was found in both human osteoclast cultures and in native osteoclasts from human bone biopsies. Moreover, agonist-evoked calcium entry indicated that the TRPV1 receptor is functionally active in vitro. Consistently, biomolecular and functional experiments showed that resiniferatoxin (RTX), a selective TRPV1 receptor agonist, increased the expression and the activity of TRAP and cathepsin K, two specific osteoclast biomarkers. The evidence that cannabinoid and vanilloid receptors are co-expressed in human osteoclasts suggests that they might cross-talk to modulate the intrinsic balance of bone mineralization and resorption by different actions of anandamide through TRPV1 and cannabinoid receptors. The presence of the endocannabinoid/endovanilloid proteins in human osteoclasts will likely have implications for the management of bone demineralization associated syndrome (i. e. osteoporosis).
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Affiliation(s)
- F Rossi
- Department of Pediatrics, Second University of Naples, Naples, Italy
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Constitutive activity at the cannabinoid CB1 receptor is required for behavioral response to noxious chemical stimulation of TRPV1: antinociceptive actions of CB1 inverse agonists. J Neurosci 2008; 28:11593-602. [PMID: 18987195 DOI: 10.1523/jneurosci.3322-08.2008] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The potential modulation of TRPV1 nociceptive activity by the CB(1) receptor was investigated here using CB(1) wild-type (WT) and knock-out (KO) mice as well as selective CB(1) inverse agonists. No significant differences were detected in baseline thermal thresholds of ICR, CB(1)WT or CB(1)KO mice. Intraplantar capsaicin produced dose- and time-related paw flinch responses in ICR and CB(1)WT mice and induced plasma extravasation yet minimal responses were seen in CB(1)KO animals with no apparent differences in TRPV1 channel expression. Capsaicin-evoked CGRP release from spinal cord tissue and capsaicin-evoked action potentials on isolated skin-nerve preparation were significantly decreased in CB(1)KO mice. Pretreatment with intraplantar galanin and bradykinin, compounds known to sensitize TRPV1 receptors, restored capsaicin-induced flinching in CB(1)KO mice. The possibility that constitutive activity at the CB(1) receptor is required to maintain the TRPV1 receptor in a "sensitized" state was tested using CB(1) inverse agonists. The CB(1) inverse agonists elicited concentration-related inhibition of capsaicin-induced calcium influx in F-11 cells and produced dose-related inhibition of capsaicin-induced flinching in ICR mice. These data suggest that constitutive activity at the CB(1) receptor maintains the TRPV1 channel in a sensitized state responsive to noxious chemical stimuli. Treatment with CB(1) inverse agonists may promote desensitization of the channel resulting in antinociceptive actions against chemical stimulus modalities. These studies propose possible therapeutic exploitation of a novel mechanism providing pain relief by CB(1) inverse agonists.
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Role of ionotropic cannabinoid receptors in peripheral antinociception and antihyperalgesia. Trends Pharmacol Sci 2008; 30:79-84. [PMID: 19070372 DOI: 10.1016/j.tips.2008.10.008] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 10/23/2008] [Accepted: 10/29/2008] [Indexed: 12/17/2022]
Abstract
Despite the wealth of information on cannabinoid-induced peripheral antihyperalgesic and antinociceptive effects in many pain models, the molecular mechanism(s) for these actions remains unknown. Although metabotropic cannabinoid receptors have important roles in many pharmacological actions of cannabinoids, recent studies have led to the recognition of a family of at least five ionotropic cannabinoid receptors (ICRs). The known ICRs are members of the family of transient receptor potential (TRP) channels and include TRPV1, TRPV2, TRPV4, TRPM8 and TRPA1. Cannabinoid activation of ICRs can result in desensitization of the TRPA1 and TRPV1 channel activities, inhibition of nociceptors and antihyperalgesia and antinociception in certain pain models. Thus, cannabinoids activate both metabotropic and ionotropic mechanisms to produce peripheral analgesic effects. Here, we provide an overview of the pharmacology of TRP channels as ICRs.
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De Petrocellis L, Deva R, Mainieri F, Schaefer M, Bisogno T, Ciccoli R, Ligresti A, Hill K, Nigam S, Appendino G, Di Marzo V. Chemical synthesis, pharmacological characterization, and possible formation in unicellular fungi of 3-hydroxy-anandamide. J Lipid Res 2008; 50:658-66. [PMID: 19017617 DOI: 10.1194/jlr.m800337-jlr200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The fungal pathogen Candida albicans transforms arachidonic acid (AA) into 3-hydroxyarachidonic acid [3R-HETE], and we investigated if its nonpathogenic and 3R-HETE-producing close relative, Dipodascopsis uninucleata, could similarly transform the endocannabinoid/endovanilloid anandamide into 3-hydroxyanandamide (3-HAEA). We found that D. uninucleata converts anandamide into 3-HAEA, and we therefore developed an enantiodivergent synthesis for this compound to study its pharmacological activity. Both enantiomers of 3-HAEA were as active as anandamide at elevating intracellular Ca2+ via TRPV1 receptors overexpressed in HEK-293 cells, while a approximately 70-90-fold and approximately 45-60-fold lower affinity at cannabinoid CB1 and CB2 receptors was instead observed. Patch clamp recordings showed that 3R-HAEA activates a TRPV1-like current in TRPV1-expressing HEK-293 cells. Thus, 3R-HETE-producing yeasts might convert anandamide released by host cells at the site of infection into 3R-HAEA, and this event might contribute to the inflammatory and algogenous responses associated to fungal diseases.
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Affiliation(s)
- L De Petrocellis
- Endocannabinoid Research Group, Institutes of Cybernetics Consiglio Nazionale delle Ricerche, Pozzuoli (Napoli), Italy
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Di Marzo V. Targeting the endocannabinoid system: to enhance or reduce? Nat Rev Drug Discov 2008; 7:438-55. [PMID: 18446159 DOI: 10.1038/nrd2553] [Citation(s) in RCA: 618] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
As our understanding of the endocannabinoids improves, so does the awareness of their complexity. During pathological states, the levels of these mediators in tissues change, and their effects vary from those of protective endogenous compounds to those of dysregulated signals. These observations led to the discovery of compounds that either prolong the lifespan of endocannabinoids or tone down their action for the potential future treatment of pain, affective and neurodegenerative disorders, gastrointestinal inflammation, obesity and metabolic dysfunctions, cardiovascular conditions and liver diseases. When moving to the clinic, however, the pleiotropic nature of endocannabinoid functions will require careful judgement in the choice of patients and stage of the disorder for treatment.
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Affiliation(s)
- Vincenzo Di Marzo
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, National Research Council (CNR), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy.
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Modulation of sensory neuron potassium conductances by anandamide indicates roles for metabolites. Br J Pharmacol 2008; 154:480-92. [PMID: 18376419 DOI: 10.1038/bjp.2008.93] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE The endogenous cannabinoid anandamide (AEA) acts at cannabinoid (CB(1)) and vanilloid (TRPV(1)) receptors. AEA also shows antinociceptive properties; although the underlying mechanism for this is not fully understood, both CB(1) and TRPV(1) may be involved. Voltage-activated Ca(2+) channels in rat-cultured dorsal root ganglion (DRG) neurons are modulated by AEA. However, AEA in different populations of neurons enhanced or attenuated KCl-evoked Ca(2+) influx; these effects were linked with soma size. The aim of this study was to determine how AEA or its metabolites might produce these variable responses. EXPERIMENTAL APPROACH The whole cell patch-clamp technique and fura-2 Ca(2+) imaging were used to characterize the actions of AEA on action potential firing and voltage-activated K(+) currents and to determine whether AEA metabolism plays any role in its effects on cultured DRG neurons. KEY RESULTS AEA attenuated multiple action potential firing evoked by 300 ms depolarizing current commands in a subpopulation of DRG neurons. Application of 1 microM AEA attenuated voltage-activated K(+) currents and the recovery of KCl-evoked Ca(2+) transients. The insensitivity of these responses to the CB(1) receptor antagonist rimonabant (100 nM) and preincubation of DRG neurons with pertussis toxin suggested that these actions are not CB(1) receptor-mediated. Preincubating DRG neurons with the fatty acid amide hydrolase (FAAH) inhibitor phenylmethylsulphonyl fluoride (PMSF) attenuated the inhibitory actions of AEA on K(+) currents and Ca(2+) influx. CONCLUSION AND IMPLICATIONS These data suggest that the products of AEA metabolism by FAAH contribute to the attenuation of K(+) conductances and altered excitability of cultured sensory neurons.
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