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Cohen K, Weizman A, Weinstein A. Modulatory effects of cannabinoids on brain neurotransmission. Eur J Neurosci 2019; 50:2322-2345. [DOI: 10.1111/ejn.14407] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 03/06/2019] [Accepted: 03/08/2019] [Indexed: 12/31/2022]
Affiliation(s)
- Koby Cohen
- Department of Behavioral Science Ariel University Science Park 40700 Ariel Israel
| | | | - Aviv Weinstein
- Department of Behavioral Science Ariel University Science Park 40700 Ariel Israel
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Long-term application of cannabinoids leads to dissociation between changes in cAMP and modulation of GABA A receptors of mouse trigeminal sensory neurons. Neurochem Int 2019; 126:74-85. [PMID: 30633953 DOI: 10.1016/j.neuint.2019.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/20/2018] [Accepted: 01/07/2019] [Indexed: 12/11/2022]
Abstract
Antinociception caused by cannabinoids may have a partial peripheral origin in addition to its central site of action. In fact, we have observed that anandamide selectively and reversibly inhibits GABAA receptors of putative nociceptive neurons of mouse trigeminal sensory ganglia via CB1 receptor activation to inhibit adenylyl cyclase and decrease cAMP with downstream posttranslational alterations. Since cannabinoids are often used chronically, we studied changes in cAMP levels and GABA-mediated currents of trigeminal neurons following 24 h application of anandamide (0.5 μM) or the synthetic cannabinoid WIN 55,212-2 (5 μM). With this protocol GABA responses were similar to control despite persistent fall in cAMP levels. Inhibition by WIN 55,212-2 of GABA effects recovered after 30 min washout and was not associated with changes in CB1 receptor expression, indicating lack of CB1 receptor inactivation and transient loss of negative coupling between CB1 receptors and GABAA receptors. The phosphodiesterase inhibitor rolipram (100 μM; 24 h) enhanced cAMP levels and GABA-mediated currents, suggesting GABAA receptors were sensitive to persistent upregulation via cAMP. While the adenylyl cyclase activator forskolin (1-20 μM) facilitated cAMP levels and GABA currents following 30 min application, this action was lost after 24 h in line with the drug limited lifespan. The PKA inhibitor PKI 14-22 (10 μM) increased cAMP without changing GABA currents. These data indicate that modulation of GABAA receptors by intracellular cAMP could be lost following persistent application of cannabinoids. Thus, these observations provide an insight into the waning antinociceptive effects of these compounds.
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Eroli F, Loonen IC, van den Maagdenberg AM, Tolner EA, Nistri A. Differential neuromodulatory role of endocannabinoids in the rodent trigeminal sensory ganglion and cerebral cortex relevant to pain processing. Neuropharmacology 2018; 131:39-50. [DOI: 10.1016/j.neuropharm.2017.12.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 10/19/2017] [Accepted: 12/05/2017] [Indexed: 12/21/2022]
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CB 1 Receptors Mediated Inhibition of ATP-Induced [Ca 2+]i Increase in Cultured Rat Spinal Dorsal Horn Neurons. Neurochem Res 2017; 43:267-275. [PMID: 29127599 DOI: 10.1007/s11064-017-2414-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 09/25/2017] [Accepted: 10/04/2017] [Indexed: 10/18/2022]
Abstract
Spinal cannabinoid receptor 1 (CB1R) and purinergic P2X receptors (P2XR) play a critical role in the process of pathological pain. Both CB1R and P2XR are expressed in spinal dorsal horn (DH) neurons. It is not clear whether CB1 receptor activation modulates the function of P2X receptor channels within dorsal horn. For this reason, we observed the effect of CP55940 (cannabinoid receptor agonist) on ATP-induced Ca2+ mobilization in cultured rat DH neurons. The changes of intracellular calcium concentration ([Ca2+]i) were detected with confocal laser scanning microscopy using fluo-4/AM as a calcium fluorescent indicator. 100 μM ATP caused [Ca2+]i increase in cultured DH neurons. ATP-evoked [Ca2+]i increase in DH neurons was blocked by chelating extracellular Ca2+ and P2 purinoceptor antagonist PPADS. At the same time, ATP-γ-S (a non-hydrolyzable ATP analogue) mimicked the ATP action, while P2Y receptor agonist ADP failed to evoke [Ca2+]i increase in cultured DH neurons. These data suggest that ATP-induced [Ca2+]i elevation in cultured DH neurons is mediated by P2X receptor. Subsequently, we noticed that, in cultured rat DH neurons, ATP-induced Ca2+ mobilization was inhibited after pretreated with CP55940 with a concentration-dependent manner, which implies that the opening of P2X receptor channels are down-regulated by activation of cannabinoid receptor. The inhibitory effect of CP55940 on ATP-induced Ca2+ response was mimicked by ACEA (CB1R agonist), but was not influenced by AM1241 (CB2R agonist). Moreover, the inhibitory effect of CP55940 on ATP-induced Ca2+ mobilization was blocked by AM251 (CB1 receptor antagonist), but was not influenced by AM630 (CB2 receptor antagonist). In addition, we also observed that forskolin (an activator of adenylate cyclase) and 8-Br-cAMP (a cell-permeable cAMP analog) reversed the inhibitory effect of CP55940, respectively. In a summary, our observations raise a possibility that CB1R rather than CB2R can downregulate the opening of P2X receptor channels in DH neurons. The reduction of cAMP/PKA signaling is a key element in the inhibitory effect of CB1R on P2X-channel-induced Ca2+ mobilization.
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Veeraraghavan P, Dekanic A, Nistri A. A study of cannabinoid-1 receptors during the early phase of excitotoxic damage to rat spinal locomotor networks in vitro. Neuroscience 2016; 333:214-28. [PMID: 27450568 DOI: 10.1016/j.neuroscience.2016.07.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 07/13/2016] [Accepted: 07/14/2016] [Indexed: 11/27/2022]
Abstract
Endocannabinoids acting on cannabinoid-1 receptors (CB1Rs) are proposed to protect brain and spinal neurons from excitotoxic damage. The ability to recover from spinal cord injury (SCI), in which excitotoxicity is a major player, is usually investigated at late times after modulation of CB1Rs whose role in the early phases of SCI remains unclear. Using the rat spinal cord in vitro as a model for studying SCI initial pathophysiology, we investigated if agonists or antagonists of CB1Rs might affect SCI induced by the excitotoxic agent kainate (KA) within 24h from a transient (1h) application of this glutamate agonist. The CB1 agonist anandamide (AEA or pharmacological block of its degradation) did not limit excitotoxic depolarization of spinal networks: cyclic adenosine monophosphate (cAMP) assay demonstrated that CB1Rs remained functional 24h later and similarly expressed among dead or survived cells. Locomotor-like network activity recorded from ventral roots could not recover with such treatments and was associated with persistent depression of synaptic transmission. Motoneurons, that are particularly vulnerable to KA, were not protected by AEA. Application of 2-arachidonoylglycerol also did not attenuate the electrophysiological and histological damage. The intensification of damage by the CB1 antagonist AM251 suggested that endocannabinoids were operative after excitotoxic stimulation, yet insufficient to contrast it efficiently. The present data indicate that the early phases of excitotoxic SCI could not be arrested by pharmacologically exploiting the endocannabinoid system, consistent with the notion that AEA and its derivatives are more useful to treat late SCI phases.
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Affiliation(s)
- Priyadharishini Veeraraghavan
- Department of Neuroscience, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
| | - Ana Dekanic
- Department of Neuroscience, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
| | - Andrea Nistri
- Department of Neuroscience, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
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Medelin M, Rancic V, Cellot G, Laishram J, Veeraraghavan P, Rossi C, Muzio L, Sivilotti L, Ballerini L. Altered development in GABA co-release shapes glycinergic synaptic currents in cultured spinal slices of the SOD1(G93A) mouse model of amyotrophic lateral sclerosis. J Physiol 2016; 594:3827-40. [PMID: 27098371 DOI: 10.1113/jp272382] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 04/07/2016] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Increased environmental risk factors in conjunction with genetic susceptibility have been proposed with respect to the remarkable variations in mortality in amyotrophic lateral sclerosis (ALS). In vitro models allow the investigation of the genetically modified counter-regulator of motoneuron toxicity and may help in addressing ALS therapy. Spinal organotypic slice cultures from a mutant form of human superoxide dismutase 1 (SOD1G93A) mouse model of ALS allow the detection of altered glycinergic inhibition in spinal microcircuits. This altered inhibition improved spinal cord excitability, affecting motor outputs in early SOD1(G93A) pathogenesis. ABSTRACT Amyotrophic lateral sclerosis (ALS) is a fatal, adult-onset neurological disease characterized by a progressive degeneration of motoneurons (MNs). In a previous study, we developed organotypic spinal cultures from an ALS mouse model expressing a mutant form of human superoxide dismutase 1 (SOD1(G93A) ). We reported the presence of a significant synaptic rearrangement expressed by these embryonic cultured networks, which may lead to the altered development of spinal synaptic signalling, which is potentially linked to the adult disease phenotype. Recent studies on the same ALS mouse model reported a selective loss of glycinergic innervation in cultured MNs, suggestive of a contribution of synaptic inhibition to MN dysfunction and degeneration. In the present study, we further exploit organotypic cultures from wild-type and SOD1(G93A) mice to investigate the development of glycine-receptor-mediated synaptic currents recorded from the interneurons of the premotor ventral circuits. We performed single cell electrophysiology, immunocytochemistry and confocal microscopy and suggest that GABA co-release may speed the decay of glycine responses altering both temporal precision and signal integration in SOD1(G93A) developing networks at the postsynaptic site. Our hypothesis is supported by the finding of an increased MN bursting activity in immature SOD1(G93A) spinal cords and by immunofluorescence microscopy detection of a longer persistence of GABA in SOD1(G93A) glycinergic terminals in cultured and ex vivo spinal slices.
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Affiliation(s)
- Manuela Medelin
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Vladimir Rancic
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Giada Cellot
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Jummi Laishram
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | | | - Chiara Rossi
- Neuroimmunology Unit, Division of Neuroscience, Institute of Experimental Neurology (INSPE), San Raffaele Scientific Institute, Milan, Italy
| | - Luca Muzio
- Neuroimmunology Unit, Division of Neuroscience, Institute of Experimental Neurology (INSPE), San Raffaele Scientific Institute, Milan, Italy
| | - Lucia Sivilotti
- Department of Neuroscience, Physiology and Pharmacology, University College London (UCL), London, UK
| | - Laura Ballerini
- Department of Life Sciences, University of Trieste, Trieste, Italy.,International School for Advanced Studies (SISSA/ISAS), Trieste, Italy
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Reddy DS, Golub VM. The Pharmacological Basis of Cannabis Therapy for Epilepsy. J Pharmacol Exp Ther 2016; 357:45-55. [PMID: 26787773 DOI: 10.1124/jpet.115.230151] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 01/15/2016] [Indexed: 12/30/2022] Open
Abstract
Recently, cannabis has been suggested as a potential alternative therapy for refractory epilepsy, which affects 30% of epilepsy, both adults and children, who do not respond to current medications. There is a large unmet medical need for new antiepileptics that would not interfere with normal function in patients with refractory epilepsy and conditions associated with refractory seizures. The two chief cannabinoids are Δ-9-tetrahyrdrocannabinol, the major psychoactive component of marijuana, and cannabidiol (CBD), the major nonpsychoactive component of marijuana. Claims of clinical efficacy in epilepsy of CBD-predominant cannabis or medical marijuana come mostly from limited studies, surveys, or case reports. However, the mechanisms underlying the antiepileptic efficacy of cannabis remain unclear. This article highlights the pharmacological basis of cannabis therapy, with an emphasis on the endocannabinoid mechanisms underlying the emerging neurotherapeutics of CBD in epilepsy. CBD is anticonvulsant, but it has a low affinity for the cannabinoid receptors CB1 and CB2; therefore the exact mechanism by which it affects seizures remains poorly understood. A rigorous clinical evaluation of pharmaceutical CBD products is needed to establish the safety and efficacy of their use in the treatment of epilepsy. Identification of mechanisms underlying the anticonvulsant efficacy of CBD is also critical for identifying other potential treatment options.
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Affiliation(s)
- Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Victoria M Golub
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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