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Forte N, Nicois A, Marfella B, Mavaro I, D'Angelo L, Piscitelli F, Scandurra A, De Girolamo P, Baldelli P, Benfenati F, Di Marzo V, Cristino L. Early endocannabinoid-mediated depolarization-induced suppression of excitation delays the appearance of the epileptic phenotype in synapsin II knockout mice. Cell Mol Life Sci 2024; 81:37. [PMID: 38214769 PMCID: PMC11072294 DOI: 10.1007/s00018-023-05029-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 10/16/2023] [Accepted: 10/31/2023] [Indexed: 01/13/2024]
Abstract
The mechanism underlying the transition from the pre-symptomatic to the symptomatic state is a crucial aspect of epileptogenesis. SYN2 is a member of a multigene family of synaptic vesicle phosphoproteins playing a fundamental role in controlling neurotransmitter release. Human SYN2 gene mutations are associated with epilepsy and autism spectrum disorder. Mice knocked out for synapsin II (SynII KO) are prone to epileptic seizures that appear after 2 months of age. However, the involvement of the endocannabinoid system, known to regulate seizure development and propagation, in the modulation of the excitatory/inhibitory balance in the epileptic hippocampal network of SynII KO mice has not been explored. In this study, we investigated the impact of endocannabinoids on glutamatergic and GABAergic synapses at hippocampal dentate gyrus granule cells in young pre-symptomatic (1-2 months old) and adult symptomatic (5-8 months old) SynII KO mice. We observed an increase in endocannabinoid-mediated depolarization-induced suppression of excitation in young SynII KO mice, compared to age-matched wild-type controls. In contrast, the endocannabinoid-mediated depolarization-induced suppression of inhibition remained unchanged in SynII KO mice at both ages. This selective alteration of excitatory synaptic transmission was accompanied by changes in hippocampal endocannabinoid levels and cannabinoid receptor type 1 distribution among glutamatergic and GABAergic synaptic terminals contacting the granule cells of the dentate gyrus. Finally, inhibition of type-1 cannabinoid receptors in young pre-symptomatic SynII KO mice induced seizures during a tail suspension test. Our results suggest that endocannabinoids contribute to maintaining network stability in a genetic mouse model of human epilepsy.
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Affiliation(s)
- Nicola Forte
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy
| | - Alessandro Nicois
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy
| | - Brenda Marfella
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy
| | - Isabella Mavaro
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy
| | - Livia D'Angelo
- Department of Veterinary Medicine and Animal Production, University of Naples Federico II, Naples, Italy
| | - Fabiana Piscitelli
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy
| | - Anna Scandurra
- Department of Biology, University of Naples Federico II, Naples, Italy
| | - Paolo De Girolamo
- Department of Veterinary Medicine and Animal Production, University of Naples Federico II, Naples, Italy
| | - Pietro Baldelli
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
- IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genoa, Italy
- IRCCS Ospedale Policlinico San Martino, Genoa, Italy
| | - Vincenzo Di Marzo
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy.
- Faculty of Medicine and Faculty of Agricultural and Food Sciences, Canada Excellence Research Chair on the Microbiome-Endocannabinoidome Axis in Metabolic Health, Université Laval, Québec City, QC, Canada.
- Heart and Lung Research Institute of Université Laval, Québec City, QC, Canada.
- Institute for Nutrition and Functional Foods, Centre NUTRISS, Université Laval, Québec City, QC, Canada.
| | - Luigia Cristino
- Institute of Biomolecular Chemistry, National Research Council of Italy, Pozzuoli (NA), Italy.
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Oddi S, Fiorenza MT, Maccarrone M. Endocannabinoid signaling in adult hippocampal neurogenesis: A mechanistic and integrated perspective. Prog Lipid Res 2023; 91:101239. [PMID: 37385352 DOI: 10.1016/j.plipres.2023.101239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 06/01/2023] [Accepted: 06/25/2023] [Indexed: 07/01/2023]
Abstract
Dentate gyrus of the hippocampus continuously gives rise to new neurons, namely, adult-born granule cells, which contribute to conferring plasticity to the mature brain throughout life. Within this neurogenic region, the fate and behavior of neural stem cells (NSCs) and their progeny result from a complex balance and integration of a variety of cell-autonomous and cell-to-cell-interaction signals and underlying pathways. Among these structurally and functionally diverse signals, there are endocannabinoids (eCBs), the main brain retrograde messengers. These pleiotropic bioactive lipids can directly and/or indirectly influence adult hippocampal neurogenesis (AHN) by modulating, both positively and negatively, multiple molecular and cellular processes in the hippocampal niche, depending on the cell type or stage of differentiation. Firstly, eCBs act directly as cell-intrinsic factors, cell-autonomously produced by NSCs following their stimulation. Secondly, in many, if not all, niche-associated cells, including some local neuronal and nonneuronal elements, the eCB system indirectly modulates the neurogenesis, linking neuronal and glial activity to regulating distinct stages of AHN. Herein, we discuss the crosstalk of the eCB system with other neurogenesis-relevant signal pathways and speculate how the hippocampus-dependent neurobehavioral effects elicited by (endo)cannabinergic medications are interpretable in light of the key regulatory role that eCBs play on AHN.
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Affiliation(s)
- Sergio Oddi
- Department of Veterinary Medicine, University of Teramo, Via R. Balzarini 1, 64100 Teramo, Italy; European Center for Brain Research/IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143 Rome, Italy.
| | - Maria Teresa Fiorenza
- European Center for Brain Research/IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143 Rome, Italy; Department of Psychology, Division of Neuroscience and "Daniel Bovet" Neurobiology Research Center, Sapienza University of Rome, Via dei Sardi 70, 00185 Rome, Italy
| | - Mauro Maccarrone
- European Center for Brain Research/IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143 Rome, Italy; Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, Via Vetoio Snc, 67100 L'Aquila, Italy
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Lafourcade CA, Sparks FT, Bordey A, Wyneken U, Mohammadi MH. Cannabinoid regulation of neurons in the dentate gyrus during epileptogenesis: Role of CB1R-associated proteins and downstream pathways. Epilepsia 2023. [PMID: 36869624 DOI: 10.1111/epi.17569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 02/27/2023] [Accepted: 03/01/2023] [Indexed: 03/05/2023]
Abstract
The hippocampal formation plays a central role in the development of temporal lobe epilepsy (TLE), a disease characterized by recurrent, unprovoked epileptic discharges. TLE is a neurologic disorder characterized by acute long-lasting seizures (i.e., abnormal electrical activity in the brain) or seizures that occur in close proximity without recovery, typically after a brain injury or status epilepticus. After status epilepticus, epileptogenic hyperexcitability develops gradually over the following months to years, resulting in the emergence of chronic, recurrent seizures. Acting as a filter or gate, the hippocampal dentate gyrus (DG) normally prevents excessive excitation from propagating through the hippocampus, and is considered a critical region in the progression of epileptogenesis in pathological conditions. Importantly, lipid-derived endogenous cannabinoids (endocannabinoids), which are produced on demand as retrograde messengers, are central regulators of neuronal activity in the DG circuit. In this review, we summarize recent findings concerning the role of the DG in controlling hyperexcitability and propose how DG regulation by cannabinoids (CBs) could provide avenues for therapeutic interventions. We also highlight possible pathways and manipulations that could be relevant for the control of hyperexcitation. The use of CB compounds to treat epilepsies is controversial, as anecdotal evidence is not always validated by clinical trials. Recent publications shed light on the importance of the DG as a region regulating incoming hippocampal excitability during epileptogenesis. We review recent findings concerning the modulation of the hippocampal DG circuitry by CBs and discuss putative underlying pathways. A better understanding of the mechanisms by which CBs exert their action during seizures may be useful to improve therapies.
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Affiliation(s)
- Carlos A Lafourcade
- Department of Biological Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, China
| | - Fraser T Sparks
- Department of Neuroscience, Columbia University, New York, New York, USA.,Current: Regeneron Pharmaceuticals, Tarrytown, New York, USA
| | - Angelique Bordey
- Department of Neurosurgery, Yale School of Medicine, New Haven, Connecticut, USA
| | - Ursula Wyneken
- Centro de Investigación e Innovación Biomédica, Laboratorio de Neurociencias, Universidad de Los Andes, Santiago, Chile.,Center of Interventional Medicine for Precision and Advanced Cellular Therapy, Santiago, Chile
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Bhattacharya D, Bartley AF, Li Q, Dobrunz LE. Bicuculline restores frequency-dependent hippocampal I/E ratio and circuit function in PGC-1ɑ null mice. Neurosci Res 2022; 184:9-18. [PMID: 35842011 PMCID: PMC10865982 DOI: 10.1016/j.neures.2022.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/22/2022] [Accepted: 07/12/2022] [Indexed: 10/31/2022]
Abstract
Altered inhibition/excitation (I/E) balance contributes to various brain disorders. Dysfunctional GABAergic interneurons enhance or reduce inhibition, resulting in I/E imbalances. Differences in short-term plasticity between excitation and inhibition cause frequency-dependence of the I/E ratio, which can be altered by GABAergic dysfunction. However, it is unknown whether I/E imbalances can be rescued pharmacologically using a single dose when the imbalance magnitude is frequency-dependent. Loss of PGC-1α (peroxisome proliferator activated receptor γ coactivator 1α) causes transcriptional dysregulation in hippocampal GABAergic interneurons. PGC-1α-/- slices have enhanced baseline inhibition onto CA1 pyramidal cells, causing increased I/E ratio and impaired circuit function. High frequency stimulation reduces the I/E ratio and recovers circuit function in PGC-1α-/- slices. Here we tested if using a low dose of bicuculline that can restore baseline I/E ratio can also rescue the frequency-dependent I/E imbalances in these mice. Remarkably, bicuculline did not reduce the I/E ratio below that of wild type during high frequency stimulation. Interestingly, bicuculline enhanced the paired-pulse ratio (PPR) of disynaptic inhibition without changing the monosynaptic inhibition PPR, suggesting that bicuculline modifies interneuron recruitment and not GABA release. Bicuculline improved CA1 output in PGC-1α-/- slices, enhancing EPSP-spike coupling to wild type levels at high and low frequencies. Our results show that it is possible to rescue frequency-dependent I/E imbalances in an animal model of transcriptional dysregulation with a single treatment.
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Affiliation(s)
- Dwipayan Bhattacharya
- Department of Neurobiology, Civitan International Research Center, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, 1825 University Blvd., Birmingham, AL, United States
| | - Aundrea F Bartley
- Department of Neurobiology, Civitan International Research Center, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, 1825 University Blvd., Birmingham, AL, United States
| | - Qin Li
- Department of Neurobiology, Civitan International Research Center, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, 1825 University Blvd., Birmingham, AL, United States
| | - Lynn E Dobrunz
- Department of Neurobiology, Civitan International Research Center, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, 1825 University Blvd., Birmingham, AL, United States.
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Aoki J, Isokawa M, Toyoda M. Space and Time Coherent Mapping for Subcellular Resolution of Imaging Mass Spectrometry. Cells 2022; 11:cells11213382. [PMID: 36359779 PMCID: PMC9653616 DOI: 10.3390/cells11213382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/14/2022] [Accepted: 10/24/2022] [Indexed: 12/02/2022] Open
Abstract
Space and time coherent mapping (STCM) is a technology developed in our laboratory for improved matrix-assisted laser desorption ionization (MALDI) time of flight (TOF) imaging mass spectrometry (IMS). STCM excels in high spatial resolutions, which probe-based scanning methods cannot attain in conventional MALDI IMS. By replacing a scanning probe with a large field laser beam, focusing ion optics, and position-sensitive detectors, STCM tracks the entire flight trajectories of individual ions throughout the ionization process and visualizes the ionization site on the sample surface with a subcellular scale of precision and a substantially short acquisition time. Results obtained in thinly sectioned leech segmental ganglia and epididymis demonstrate that STCM IMS is highly suited for (1) imaging bioactive lipid messengers such as endocannabinoids and the mediators of neuronal activities in situ with spatial resolution sufficient to detail subcellular localization, (2) integrating resultant images in mass spectrometry to optically defined cell anatomy, and (3) assembling a stack of ion maps derived from mass spectra for cluster analysis. We propose that STCM IMS is the choice over a probe-based scanning mass spectrometer for high-resolution single-cell molecular imaging.
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Affiliation(s)
- Jun Aoki
- Center for Biosystems Dynamics Research, RIKEN, Saitama 351-0198, Japan
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
- Correspondence:
| | - Masako Isokawa
- Forefront Research Center, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Michisato Toyoda
- Forefront Research Center, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
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Winters BL, Vaughan CW. Mechanisms of endocannabinoid control of synaptic plasticity. Neuropharmacology 2021; 197:108736. [PMID: 34343612 DOI: 10.1016/j.neuropharm.2021.108736] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 01/13/2023]
Abstract
The endogenous cannabinoid transmitter system regulates synaptic transmission throughout the nervous system. Unlike conventional transmitters, specific stimuli induce synthesis of endocannabinoids (eCBs) in the postsynaptic neuron, and these travel backwards to modulate presynaptic inputs. In doing so, eCBs can induce short-term changes in synaptic strength and longer-term plasticity. While this eCB regulation is near ubiquitous, it displays major regional and synapse specific variations with different synapse specific forms of short-versus long-term plasticity throughout the brain. These differences are due to the plethora of pre- and postsynaptic mechanisms which have been implicated in eCB signalling, the intricacies of which are only just being realised. In this review, we shall describe the current understanding and highlight new advances in this area, with a focus on the retrograde action of eCBs at CB1 receptors (CB1Rs).
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Affiliation(s)
- Bryony Laura Winters
- Pain Management Research Institute, Kolling Institute of Medical Research, Northern Clinical School, University of Sydney at Royal North Shore Hospital, NSW, Australia.
| | - Christopher Walter Vaughan
- Pain Management Research Institute, Kolling Institute of Medical Research, Northern Clinical School, University of Sydney at Royal North Shore Hospital, NSW, Australia
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Multiple cannabinoid signaling cascades powerfully suppress recurrent excitation in the hippocampus. Proc Natl Acad Sci U S A 2021; 118:2017590118. [PMID: 33468648 DOI: 10.1073/pnas.2017590118] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recurrent excitatory neural networks are unstable. In the hippocampus, excitatory mossy cells (MCs) receive strong excitatory inputs from dentate granule cells (GCs) and project back onto the proximal dendrites of GCs. By targeting the ipsi- and contralateral dentate gyrus (DG) along the dorsoventral axis of the hippocampus, MCs form an extensive recurrent excitatory circuit (GC-MC-GC) whose dysregulation can promote epilepsy. We recently reported that a physiologically relevant pattern of MC activity induces a robust form of presynaptic long-term potentiation (LTP) of MC-GC transmission which enhances GC output. Left unchecked, this LTP may interfere with DG-dependent learning, like pattern separation-which relies on sparse GC firing-and may even facilitate epileptic activity. Intriguingly, MC axons display uniquely high expression levels of type-1 cannabinoid receptors (CB1Rs), but their role at MC-GC synapses is poorly understood. Using rodent hippocampal slices, we report that constitutively active CB1Rs, presumably via βγ subunits, selectively inhibited MC inputs onto GCs but not MC inputs onto inhibitory interneurons or CB1R-sensitive inhibitory inputs onto GCs. Tonic CB1R activity also inhibited LTP and GC output. Furthermore, brief endocannabinoid release from GCs dampened MC-GC LTP in two mechanistically distinct ways: during induction via βγ signaling and before induction via αi/o signaling in a form of presynaptic metaplasticity. Lastly, a single in vivo exposure to exogenous cannabinoids was sufficient to induce this presynaptic metaplasticity. By dampening excitatory transmission and plasticity, tonic and phasic CB1R activity at MC axon terminals may preserve the sparse nature of the DG and protect against runaway excitation.
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Experience-Dependent Inhibitory Plasticity Is Mediated by CCK+ Basket Cells in the Developing Dentate Gyrus. J Neurosci 2021; 41:4607-4619. [PMID: 33906898 DOI: 10.1523/jneurosci.1207-20.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 11/21/2022] Open
Abstract
Early postnatal experience shapes both inhibitory and excitatory networks in the hippocampus. However, the underlying circuit plasticity is unclear. Using an enriched environment (EE) paradigm during the preweaning period in mice of either sex, we assessed the circuit plasticity of inhibitory cell types in the hippocampus. We found that cholecystokinin (CCK)-expressing basket cells strongly increased somatic inhibition on the excitatory granular cells (GCs) following EE, whereas another pivotal inhibitory cell type, parvalbumin (PV)-expressing cells, did not show changes. Using electrophysiological analysis and the use of cannabinoid receptor 1 (CB1R) agonist WIN 55 212-2, we demonstrate that the change in somatic inhibition from CCK+ neurons increases CB1R-mediated inhibition in the circuit. By inhibiting activity of the entorhinal cortex (EC) using a chemogenetic approach, we further demonstrate that the activity of the projections from the EC mediates the developmental assembly of CCK+ basket cell network. Altogether, our study places the experience-dependent remodeling of CCK+ basket cell innervation as a central process to adjust inhibition in the dentate gyrus and shows that cortical inputs to the hippocampus play an instructional role in controlling the refinement of the synaptic connections during the preweaning period.SIGNIFICANCE STATEMENT Brain plasticity is triggered by experience during postnatal brain development and shapes the maturing neural circuits. In humans, altered experience-dependent plasticity can have long-lasting detrimental effects on circuit function and lead to psychiatric disorders. Yet, the cellular mechanisms governing how early experience fine-tunes the maturing synaptic network is not fully understood. Here, taking advantage of an enrichment-housing paradigm, we unravel a new plasticity mechanism involved in the maintenance of the inhibitory to excitatory balance in the hippocampus. Our findings demonstrate that cortical activity instructs the assembly of the CCK+ basket cell network. Considering the importance of this specific cell type for learning and memory, experience-dependent remodeling of CCK+ cells may be a critical determinant for establishing appropriate neural networks.
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Wu MM, Thayer SA. HIV Tat Protein Selectively Impairs CB 1 Receptor-Mediated Presynaptic Inhibition at Excitatory But Not Inhibitory Synapses. eNeuro 2020; 7:ENEURO.0119-20.2020. [PMID: 32471847 PMCID: PMC7307634 DOI: 10.1523/eneuro.0119-20.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 04/17/2020] [Accepted: 04/26/2020] [Indexed: 02/06/2023] Open
Abstract
Despite the success of antiretroviral therapy in suppressing viral load, nearly half of the 37 million people infected with HIV experience cognitive and motor impairments, collectively classified as HIV-associated neurocognitive disorders (HAND). In the CNS, HIV-infected microglia release neurotoxic agents that act indirectly to elicit excitotoxic synaptic injury. HIV trans-activator of transcription (Tat) protein is one such neurotoxin that is thought to play a major role in the neuropathogenesis of HAND. The endocannabinoid (eCB) system provides on-demand neuroprotection against excitotoxicity, and exogenous cannabinoids attenuate neurotoxicity in animal models of HAND. Whether this neuroprotective system is altered in the presence of HIV is unknown. Here, we examined the effects of Tat on the eCB system in rat primary hippocampal cultures. Using whole-cell patch-clamp electrophysiology, we measured changes in retrograde eCB signaling following exposure to Tat. Treatment with Tat significantly reduced the magnitude of depolarization-induced suppression of excitation (DSE) in a graded manner over the course of 48 h. Interestingly, Tat did not alter this form of short-term synaptic plasticity at inhibitory terminals. The Tat-induced decrease in eCB signaling resulted from impaired CB1 receptor (CB1R)-mediated presynaptic inhibition of glutamate release. This novel loss-of-function was particularly dramatic for low-efficacy agonists such as the eCB 2-arachidonoylglycerol (2-AG) and Δ9-tetrahydrocannabinol (Δ9-THC), the main psychoactive ingredient in marijuana. Our observation that HIV Tat decreases CB1R function in vitro suggests that eCB-mediated neuroprotection may be reduced in vivo; this effect of Tat may contribute to synaptodendritic injury in HAND.
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Affiliation(s)
- Mariah M Wu
- Graduate Program in Neuroscience, University of Minnesota Medical School, Minneapolis, MN 55455
| | - Stanley A Thayer
- Graduate Program in Neuroscience, University of Minnesota Medical School, Minneapolis, MN 55455
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455
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10
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Peñasco S, Rico-Barrio I, Puente N, Gómez-Urquijo SM, Fontaine CJ, Egaña-Huguet J, Achicallende S, Ramos A, Reguero L, Elezgarai I, Nahirney PC, Christie BR, Grandes P. Endocannabinoid long-term depression revealed at medial perforant path excitatory synapses in the dentate gyrus. Neuropharmacology 2019; 153:32-40. [PMID: 31022405 DOI: 10.1016/j.neuropharm.2019.04.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 03/28/2019] [Accepted: 04/18/2019] [Indexed: 12/22/2022]
Abstract
The endocannabinoid system modulates synaptic plasticity in the hippocampus, but a link between long-term synaptic plasticity and the type 1 cannabinoid (CB1) receptor at medial perforant path (MPP) synapses remains elusive. Here, immuno-electron microscopy in adult mice showed that ∼26% of the excitatory synaptic terminals in the middle 1/3 of the dentate molecular layer (DML) contained CB1 receptors, and field excitatory postsynaptic potentials evoked by MPP stimulation were inhibited by CB1 receptor activation. In addition, MPP stimulation at 10 Hz for 10 min triggered CB1 receptor-dependent excitatory long-term depression (eCB-eLTD) at MPP synapses of wild-type mice but not on CB1-knockout mice. This eCB-eLTD was group I mGluR-dependent, required intracellular calcium influx and 2-arachydonoyl-glycerol (2-AG) synthesis but did not depend on N-methyl-d-aspartate (NMDA) receptors. Overall, these results point to a functional role for CB1 receptors with eCB-eLTD at DML MPP synapses and further involve these receptors in memory processing within the adult brain.
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Affiliation(s)
- Sara Peñasco
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Irantzu Rico-Barrio
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Nagore Puente
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Sonia María Gómez-Urquijo
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Christine J Fontaine
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada
| | - Jon Egaña-Huguet
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Svein Achicallende
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Almudena Ramos
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Leire Reguero
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Izaskun Elezgarai
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain
| | - Patrick C Nahirney
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada
| | - Brian R Christie
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada
| | - Pedro Grandes
- Department of Neurosciences, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Achucarro Basque Center for Neuroscience, Science Park of the University of the Basque Country UPV/EHU, E-48940, Leioa, Spain; Division of Medical Sciences, University of Victoria, Victoria, British Columbia, V8P 5C2, Canada.
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11
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Prenatal immune activation potentiates endocannabinoid-related plasticity of inhibitory synapses in the hippocampus of adolescent rat offspring. Eur Neuropsychopharmacol 2018; 28:1405-1417. [PMID: 30257799 DOI: 10.1016/j.euroneuro.2018.09.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 08/17/2018] [Accepted: 09/05/2018] [Indexed: 12/29/2022]
Abstract
There is strong evidence that immune activation from prenatal infection increases the risk for offspring to develop schizophrenia. The endocannabinoid (eCB) system has been implicated in the pathophysiology of schizophrenia while models of cortical dysfunction postulate an imbalance between neuronal excitation and inhibition in the disorder. The current study examined the impact of prenatal immune activation on eCB-mediated inhibitory mechanisms. We compared two forms of eCB-related plasticity of evoked inhibitory postsynaptic currents, namely depolarization-induced suppression of inhibition (DSI) and metabotropic glutamate receptor-induced long term depression (mGluR-iLTD), in both the dorsal and ventral hippocampus between adolescent offspring from rat dams that received either saline or bacterial lipopolysaccharide (LPS) during pregnancy. Compared to prenatal saline offspring, prenatal LPS offspring displayed prolonged DSI and stronger mGluR-iLTD in the dorsal and ventral hippocampus, respectively. The sensitivity of mGluR-iLTD to the CB1 receptor antagonist AM251 was also lower in the dorsal hippocampus of prenatal LPS compared to prenatal saline offspring. Testing whether changes in eCB receptor signaling or levels could contribute to these changes in inhibitory transmission, we found region specific increases in 2-arachidonoylglycerol-stimulated signaling and in basal and mGluR-induced levels of anandamide in prenatal LPS offspring when compared to prenatal saline offspring. Our findings indicate that prenatal immune activation can lead to long-term changes in eCB-related plasticity of hippocampal inhibitory synaptic transmission in adolescent rat offspring. Perturbation of the eCB system resulting from prenatal immune activation could represent a mechanism linking early life immune events to the development of psychopathology in adolescence.
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Prefrontal cortex-dependent innate behaviors are altered by selective knockdown of Gad1 in neuropeptide Y interneurons. PLoS One 2018; 13:e0200809. [PMID: 30024942 PMCID: PMC6053188 DOI: 10.1371/journal.pone.0200809] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 06/09/2018] [Indexed: 12/23/2022] Open
Abstract
GABAergic dysfunction has been implicated in a variety of neurological and psychiatric disorders, including anxiety disorders. Anxiety disorders are the most common type of psychiatric disorder during adolescence. There is a deficiency of GABAergic transmission in anxiety, and enhancement of GABA transmission through pharmacological means reduces anxiety behaviors. GAD67—the enzyme responsible for GABA production–has been linked to anxiety disorders. One class of GABAergic interneurons, Neuropeptide Y (NPY) expressing cells, is abundantly found in brain regions associated with anxiety and fear learning, including prefrontal cortex, hippocampus and amygdala. Additionally, NPY itself has been shown to have anxiolytic effects, and loss of NPY+ interneurons enhances anxiety behaviors. A previous study showed that knockdown of Gad1 from NPY+ cells led to reduced anxiety behaviors in adult mice. However, the role of GABA release from NPY+ interneurons in adolescent anxiety is unclear. Here we used a transgenic mouse that reduces GAD67 in NPY+ cells (NPYGAD1-TG) through Gad1 knockdown and tested for effects on behavior in adolescent mice. Adolescent NPYGAD1-TG mice showed enhanced anxiety-like behavior and sex-dependent changes in locomotor activity. We also found enhancement in two other innate behavioral tasks, nesting construction and social dominance. In contrast, fear learning was unchanged. Because we saw changes in behavioral tasks dependent upon prefrontal cortex and hippocampus, we investigated the extent of GAD67 knockdown in these regions. Immunohistochemistry revealed a 40% decrease in GAD67 in NPY+ cells in prefrontal cortex, indicating a significant but incomplete knockdown of GAD67. In contrast, there was no decrease in GAD67 in NPY+ cells in hippocampus. Consistent with this, there was no change in inhibitory synaptic transmission in hippocampus. Our results show the behavioral impact of cell-specific interneuron dysfunction and suggest that GABA release by NPY+ cells is important for regulating innate prefrontal cortex-dependent behavior in adolescents.
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Drug-Induced Alterations of Endocannabinoid-Mediated Plasticity in Brain Reward Regions. J Neurosci 2017; 36:10230-10238. [PMID: 27707960 DOI: 10.1523/jneurosci.1712-16.2016] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/25/2016] [Indexed: 12/21/2022] Open
Abstract
The endocannabinoid (eCB) system has emerged as one of the most important mediators of physiological and pathological reward-related synaptic plasticity. eCBs are retrograde messengers that provide feedback inhibition, resulting in the suppression of neurotransmitter release at both excitatory and inhibitory synapses, and they serve a critical role in the spatiotemporal regulation of both short- and long-term synaptic plasticity that supports adaptive learning of reward-motivated behaviors. However, mechanisms of eCB-mediated synaptic plasticity in reward areas of the brain are impaired following exposure to drugs of abuse. Because of this, it is theorized that maladaptive eCB signaling may contribute to the development and maintenance of addiction-related behavior. Here we review various forms of eCB-mediated synaptic plasticity present in regions of the brain involved in reward and reinforcement and explore the potential physiological relevance of maladaptive eCB signaling to addiction vulnerability.
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Nazari M, Komaki A, Salehi I, Sarihi A, Shahidi S, Komaki H, Ganji A. Interactive effects of AM251 and baclofen on synaptic plasticity in the rat dentate gyrus. Brain Res 2016; 1651:53-60. [DOI: 10.1016/j.brainres.2016.09.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 09/16/2016] [Accepted: 09/19/2016] [Indexed: 01/11/2023]
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Sugaya Y, Yamazaki M, Uchigashima M, Kobayashi K, Watanabe M, Sakimura K, Kano M. Crucial Roles of the Endocannabinoid 2-Arachidonoylglycerol in the Suppression of Epileptic Seizures. Cell Rep 2016; 16:1405-1415. [PMID: 27452464 DOI: 10.1016/j.celrep.2016.06.083] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 05/01/2016] [Accepted: 06/21/2016] [Indexed: 01/13/2023] Open
Abstract
Endocannabinoid signaling is considered to suppress excessive excitability of neural circuits and to protect the brain from seizures. However, the precise mechanisms of this effect are poorly understood. Here, we report that 2-arachidonoylglycerol (2-AG), one of the two major endocannabinoids, is crucial for suppressing seizures. We found that kainate-induced seizures in mice lacking the 2-AG synthesizing enzyme, diacylglycerol lipase α, were much more severe compared with those in cannabinoid CB1 receptor knockout mice and were comparable to those in mice lacking both CB1- and CB2-receptor-mediated signaling. In the dentate gyrus, 2-AG suppressed excitatory input around the inner and middle molecular layers through CB1 and presumably CB2 receptors, respectively. This 2-AG-mediated suppression contributed to decreased granule cell excitability and the dampening of seizures. Furthermore, lack of 2-AG signaling enhanced kindling epileptogenesis and spontaneous seizures after kainate-induced status epilepticus. These results highlight critical roles of 2-AG signaling in the suppression of epileptic seizures.
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Affiliation(s)
- Yuki Sugaya
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Motokazu Uchigashima
- Department of Anatomy and Embryology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Kenta Kobayashi
- Section of Viral Vector Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Masahiko Watanabe
- Department of Anatomy and Embryology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
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Gholami Pourbadie H, Naderi N, Janahmadi M, Mehranfard N, Motamedi F. Calcium channel blockade attenuates abnormal synaptic transmission in the dentate gyrus elicited by entorhinal amyloidopathy. Synapse 2016; 70:408-17. [DOI: 10.1002/syn.21915] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 05/24/2016] [Accepted: 05/25/2016] [Indexed: 12/15/2022]
Affiliation(s)
- Hamid Gholami Pourbadie
- Department of Physiology and Pharmacology; Pasteur Institute of Iran; Tehran Iran
- Neuroscience Research Center; Shahid Beheshti University of Medical Sciences; Tehran Iran
- Department of Physiology; Faculty of Medicine, Shahid Beheshti University of Medical Sciences; Tehran Iran
| | - Nima Naderi
- Neuroscience Research Center; Shahid Beheshti University of Medical Sciences; Tehran Iran
- Department of Pharmacology and Toxicology; School of Pharmacy, Shahid Beheshti University of Medical Sciences; Tehran Iran
| | - Mahyar Janahmadi
- Neurophysiology Research Center; Faculty of Medicine, Shahid Beheshti University of Medical Sciences; Tehran Iran
| | - Nasrin Mehranfard
- Neuroscience Research Center; Shahid Beheshti University of Medical Sciences; Tehran Iran
- Department of Physiology; Faculty of Medicine, Shahid Beheshti University of Medical Sciences; Tehran Iran
| | - Fereshteh Motamedi
- Neuroscience Research Center; Shahid Beheshti University of Medical Sciences; Tehran Iran
- Department of Physiology; Faculty of Medicine, Shahid Beheshti University of Medical Sciences; Tehran Iran
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Wang X, Wang Y, Zhang C, Liu C, Zhao B, Wei N, Zhang JG, Zhang K. CB1 receptor antagonism prevents long-term hyperexcitability after head injury by regulation of dynorphin-KOR system and mGluR5 in rat hippocampus. Brain Res 2016; 1646:174-181. [PMID: 27262683 DOI: 10.1016/j.brainres.2016.05.055] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 05/28/2016] [Accepted: 05/31/2016] [Indexed: 01/23/2023]
Abstract
Both endocannabinoids and dynorphin are feedback messengers in nervous system that act at the presynaptic nerve terminal to inhibit transmitter release. Many studies showed the cannabinoid-opioid cross-modulation in antinociception, hypothermia, sedation and reward. The aim of this study was to assess the influence of early application of cannabinoid type 1 (CB1) receptor antagonism SR141716A after brain injury on dynorphin-κ opioid receptor (KOR) system and the expression of metabotropic glutamate receptors (mGluRs) in a rat model of fluid percussion injury (FPI). Firstly, seizure latency induced by pentylenetetrazole was significantly prolonged 6 weeks after brain injury in group of SR141716A treatment. Then, PCR and western blot showed that SR141716A inhibited the long-term up-regulation of CB1 receptors in hippocampus. However, SR141716A resulted in long-term potentiation of dynorphin release and did not influence the up-regulation of KOR in hippocampus after brain injury. Furthermore, SR141716A reverse the overexpression of mGluR5 in the late stage of brain injury. We propose that during the induction of epileptogenesis after brain injury, early application of CB1 receptor antagonism could prevent long-term hyperexcitability by up-regulation of dynorphin-KOR system and prevention of mGluR5 induced epileptogenesis in hippocampus.
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Affiliation(s)
- Xiu Wang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Key Laboratory of Neurostimulation, Tiantan xili 6, Dongcheng, Beijing 100050, China
| | - Yao Wang
- Beijing Jingmei Group General Hospital, Heishan Street 18, Mentougou, Beijing 102300, China
| | - Chao Zhang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Key Laboratory of Neurostimulation, Tiantan xili 6, Dongcheng, Beijing 100050, China
| | - Chang Liu
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Key Laboratory of Neurostimulation, Tiantan xili 6, Dongcheng, Beijing 100050, China
| | - Baotian Zhao
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Key Laboratory of Neurostimulation, Tiantan xili 6, Dongcheng, Beijing 100050, China
| | - Naili Wei
- Department of Neurosurgery, The Second Hospital of Lanzhou University, Chengguan District, Lanzhou, Gansu 730030, China
| | - Jian-Guo Zhang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Neurosurgical Institute, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Key Laboratory of Neurostimulation, Tiantan xili 6, Dongcheng, Beijing 100050, China
| | - Kai Zhang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Neurosurgical Institute, Tiantan xili 6, Dongcheng, Beijing 100050, China; Beijing Key Laboratory of Neurostimulation, Tiantan xili 6, Dongcheng, Beijing 100050, China.
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Interneuron Transcriptional Dysregulation Causes Frequency-Dependent Alterations in the Balance of Inhibition and Excitation in Hippocampus. J Neurosci 2016; 35:15276-90. [PMID: 26586816 DOI: 10.1523/jneurosci.1834-15.2015] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Circuit dysfunction in complex brain disorders such as schizophrenia and autism is caused by imbalances between inhibitory and excitatory synaptic transmission (I/E). Short-term plasticity differentially alters responses from excitatory and inhibitory synapses, causing the I/E ratio to change as a function of frequency. However, little is known about I/E ratio dynamics in complex brain disorders. Transcriptional dysregulation in interneurons, particularly parvalbumin interneurons, is a consistent pathophysiological feature of schizophrenia. Peroxisome proliferator activated receptor γ coactivator 1α (PGC-1α) is a transcriptional coactivator that in hippocampus is highly concentrated in inhibitory interneurons and regulates parvalbumin transcription. Here, we used PGC-1α(-/-) mice to investigate effects of interneuron transcriptional dysregulation on the dynamics of the I/E ratio at the synaptic and circuit level in hippocampus. We find that loss of PGC-1α increases the I/E ratio onto CA1 pyramidal cells in response to Schaffer collateral stimulation in slices from young adult mice. The underlying mechanism is enhanced basal inhibition, including increased inhibition from parvalbumin interneurons. This decreases the spread of activation in CA1 and dramatically limits pyramidal cell spiking, reducing hippocampal output. The I/E ratio and CA1 output are partially restored by paired-pulse stimulation at short intervals, indicating frequency-dependent effects. However, circuit dysfunction persists, indicated by alterations in kainate-induced gamma oscillations and impaired nest building. Together, these results show that transcriptional dysregulation in hippocampal interneurons causes frequency-dependent alterations in I/E ratio and circuit function, suggesting that PGC-1α deficiency in psychiatric and neurological disorders contributes to disease by causing functionally relevant alterations in I/E balance. SIGNIFICANCE STATEMENT Alteration in the inhibitory and excitatory synaptic transmission (I/E) balance is a fundamental principle underlying the circuit dysfunction observed in many neuropsychiatric and neurodevelopmental disorders. The I/E ratio is dynamic, continuously changing because of synaptic short-term plasticity. We show here that transcriptional dysregulation in interneurons, particularly parvalbumin interneurons, causes frequency-dependent alterations in the I/E ratio and in circuit function in hippocampus. Peroxisome proliferator activated receptor γ coactivator 1α (PGC-1α-deficient) mice have enhanced inhibition in CA1, the opposite of what is seen in cortex. This study fills an important gap in current understanding of how changes in inhibition in complex brain disorders affect I/E dynamics, leading to region-specific circuit dysfunction and behavioral impairment. This study also provides a conceptual framework for analyzing the effects of short-term plasticity on the I/E balance in disease models.
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Bartley AF, Dobrunz LE. Short-term plasticity regulates the excitation/inhibition ratio and the temporal window for spike integration in CA1 pyramidal cells. Eur J Neurosci 2015; 41:1402-15. [PMID: 25903384 DOI: 10.1111/ejn.12898] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 02/27/2015] [Accepted: 03/16/2015] [Indexed: 12/21/2022]
Abstract
Many neurodevelopmental and neuropsychiatric disorders involve an imbalance between excitation and inhibition caused by synaptic alterations. The proper excitation/inhibition (E/I) balance is especially critical in CA1 pyramidal cells, because they control hippocampal output. Activation of Schaffer collateral axons causes direct excitation of CA1 pyramidal cells, quickly followed by disynaptic feedforward inhibition, stemming from synaptically induced firing of GABAergic interneurons. Both excitatory and inhibitory synapses are modulated by short-term plasticity, potentially causing dynamic tuning of the E/I ratio. However, the effects of short-term plasticity on the E/I ratio in CA1 pyramidal cells are not yet known. To determine this, we recorded disynaptic inhibitory postsynaptic currents and the E/I ratio in CA1 pyramidal cells in acute hippocampal slices from juvenile mice. We found that, whereas inhibitory synapses had paired-pulse depression, disynaptic inhibition instead had paired-pulse facilitation (≤ 200-ms intervals), caused by increased recruitment of feedforward interneurons. Although enhanced disynaptic inhibition helped to constrain paired-pulse facilitation of excitation, the E/I ratio was still larger on the second pulse, increasing pyramidal cell spiking. Surprisingly, this occurred without compromising the precision of spike timing. The E/I balance regulates the temporal spike integration window from multiple inputs; here, we showed that paired-pulse stimulation can broaden the spike integration window. Together, our findings show that the combined effects of short-term plasticity of disynaptic inhibition and monosynaptic excitation alter the E/I balance in CA1 pyramidal cells, leading to dynamic modulation of spike probability and the spike integration window. Short-term plasticity is therefore an important mechanism for modulating signal processing of hippocampal output.
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Affiliation(s)
- Aundrea F Bartley
- Department of Neurobiology, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, 1825 University Blvd, SHEL 902, Birmingham, AL, 35294, USA
| | - Lynn E Dobrunz
- Department of Neurobiology, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, 1825 University Blvd, SHEL 902, Birmingham, AL, 35294, USA
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20
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Compartment-specific modulation of GABAergic synaptic transmission by TRPV1 channels in the dentate gyrus. J Neurosci 2015; 34:16621-9. [PMID: 25505315 DOI: 10.1523/jneurosci.3635-14.2014] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The transient receptor potential TRPV1 or vanilloid receptor is a nonselective ligand-gated channel highly expressed in primary sensory neurons where it mediates nociception. TRPV1 is also expressed in the brain where its activation depresses excitatory synaptic transmission. Whether TRPV1 also regulates inhibitory synapses in the brain is unclear. Here, using a combination of pharmacology, electrophysiology, and an in vivo knockdown strategy, we report that TRPV1 activation by capsaicin or by the endocannabinoid anandamide depresses somatic, but not dendritic inhibitory transmission in both rat and mouse dentate gyrus. The effect on somatic inhibition was absent in TRPV1 knock-out mice and was also eliminated by two different TRPV1 shRNAs expressed in dentate granule cells, strongly supporting a functional role for TRPV1 in modulating GABAergic synaptic function. Moreover, TRPV1-mediated depression occurs independently of GABA release, requires postsynaptic Ca(2+) rise and activation of calcineurin, and is likely due to clathrin-dependent internalization of GABA receptors. Altogether, these findings reveal a novel form of compartment-specific regulation whereby TRPV1 channels can modify synaptic function in the brain.
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21
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Endocannabinoid CB1 receptor-mediated rises in Ca(2+) and depolarization-induced suppression of inhibition within the laterodorsal tegmental nucleus. Brain Struct Funct 2015; 221:1255-77. [PMID: 25573246 DOI: 10.1007/s00429-014-0969-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/12/2014] [Indexed: 12/21/2022]
Abstract
Cannabinoid type 1 receptors (CB1Rs) are functionally active within the laterodorsal tegmental nucleus (LDT), which is critically involved in control of rapid eye movement sleep, cortical arousal, and motivated states. To further characterize the cellular consequences of activation of CB1Rs in this nucleus, we examined whether CB1R activation led to rises in intracellular Ca(2+) ([Ca(2+)]i) and whether processes shown in other regions to involve endocannabinoid (eCB) transmission were present in the LDT. Using a combination of Ca(2+) imaging in multiple cells loaded with Ca(2+) imaging dye via 'bulk-loading' or in single cells loaded with dye via a patch-clamp electrode, we found that WIN 55212-2 (WIN-2), a potent CB1R agonist, induced increases in [Ca(2+)]i which were sensitive to AM251, a CB1R antagonist. A proportion of rises persisted in TTX and/or low-extracellular Ca(2+) conditions. Attenuation of these increases by a reversible inhibitor of sarcoplasmic reticulum Ca(2+)-ATPases, suggests these rises occurred following release of Ca(2+) from intracellular stores. Under voltage clamp conditions, brief, direct depolarization of LDT neurons resulted in a decrease in the frequency and amplitude of AM251-sensitive, inhibitory postsynaptic currents (IPSCs), which was an action sensitive to presence of a Ca(2+) chelator. Finally, actions of DHPG, a mGlu1R agonist, on IPSC activity were examined and found to result in an AM251- and BAPTA-sensitive inhibition of both the frequency and amplitude of sIPSCs. Taken together, our data further characterize CB1R and eCB actions in the LDT and indicate that eCB transmission could play a role in the processes governed by this nucleus.
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Melis M, Greco B, Tonini R. Interplay between synaptic endocannabinoid signaling and metaplasticity in neuronal circuit function and dysfunction. Eur J Neurosci 2014; 39:1189-201. [PMID: 24712998 DOI: 10.1111/ejn.12501] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 12/23/2013] [Accepted: 01/07/2014] [Indexed: 11/29/2022]
Abstract
Synaptic neuromodulation acts across different functional domains to regulate cognitive processing and behavior. Recent challenges are related to elucidating the molecular and cellular mechanisms through which neuromodulatory pathways act on multiple time scales to signal state-dependent contingencies at the synaptic level or to stabilise synaptic connections during behavior. Here, we present a framework with the synaptic neuromodulators endocannabinoids (eCBs) as key players in dynamic synaptic changes. Modulation of various molecular components of the eCB pathway yields interconnected functional activation states of eCB signaling (prior, tonic, and persistent), which may contribute to metaplastic control of synaptic and behavioral functions in health and disease. The emerging picture supports aberrant metaplasticity as a contributor to cognitive dysfunction associated with several pathological states in which eCB signaling, or other neuromodulatory pathways, are deregulated.
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Affiliation(s)
- Miriam Melis
- Department of Biomedical Sciences, Division of Neuroscience and Clinical Pharmacology, University of Cagliari, Cagliari, Italy
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Wang XH, Wu Y, Yang XF, Miao Y, Zhang CQ, Dong LD, Yang XL, Wang Z. Cannabinoid CB1 receptor signaling dichotomously modulates inhibitory and excitatory synaptic transmission in rat inner retina. Brain Struct Funct 2014; 221:301-16. [DOI: 10.1007/s00429-014-0908-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 09/26/2014] [Indexed: 12/01/2022]
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Patogeneza uzależnień – problem wciąż aktualny. ALCOHOLISM AND DRUG ADDICTION 2014. [DOI: 10.1016/s0867-4361(14)70011-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Thr136Ile polymorphism of human vesicular monoamine transporter-1 (SLC18A1 gene) influences its transport activity in vitro. Neural Plast 2013; 2012:945373. [PMID: 23213575 PMCID: PMC3504448 DOI: 10.1155/2012/945373] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 09/22/2012] [Accepted: 09/23/2012] [Indexed: 12/23/2022] Open
Abstract
The hippocampus has the extraordinary capacity to process and store information. Consequently, there is an intense interest in the mechanisms that underline learning and memory. Synaptic plasticity has been hypothesized to be the neuronal substrate for learning. Ca2+ and Ca2+-activated kinases control cellular processes of most forms of hippocampal synapse plasticity. In this paper, I aim to integrate our current understanding of Ca2+-mediated synaptic plasticity and metaplasticity in motivational and reward-related learning in the hippocampus. I will introduce two representative neuromodulators that are widely studied in reward-related learning (e.g., ghrelin and endocannabinoids) and show how they might contribute to hippocampal neuron activities and Ca2+-mediated signaling processes in synaptic plasticity. Additionally, I will discuss functional significance of these two systems and their signaling pathways for its relevance to maladaptive reward learning leading to addiction.
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Hofmann ME, Frazier CJ. Marijuana, endocannabinoids, and epilepsy: potential and challenges for improved therapeutic intervention. Exp Neurol 2011; 244:43-50. [PMID: 22178327 DOI: 10.1016/j.expneurol.2011.11.047] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 11/25/2011] [Accepted: 11/29/2011] [Indexed: 10/14/2022]
Abstract
Phytocannabinoids isolated from the cannabis plant have broad potential in medicine that has been well recognized for many centuries. It is presumed that these lipid soluble signaling molecules exert their effects in both the central and peripheral nervous system in large part through direct interaction with metabotropic cannabinoid receptors. These same receptors are also targeted by a variety of endogenous cannabinoids including 2-arachidonoyl glycerol and anandamide. Significant effort over the last decade has produced an enormous advance in our understanding of both the cellular and the synaptic physiology of endogenous lipid signaling systems. This increase in knowledge has left us better prepared to carefully evaluate the potential for both natural and synthetic cannabinoids in the treatment of a variety of neurological disorders. In the case of epilepsy, long standing interest in therapeutic approaches that target endogenous cannabinoid signaling systems are, for the most part, not well justified by available clinical data from human epileptics. Nevertheless, basic science experiments have clearly indicated a key role for endogenous cannabinoid signaling systems in moment to moment regulation of neuronal excitability. Further it has become clear that these systems can both alter and be altered by epileptiform activity in a wide range of in vitro and in vivo models of epilepsy. Collectively these observations suggest clear potential for effective therapeutic modulation of endogenous cannabinoid signaling systems in the treatment of human epilepsy, and in fact, further highlight key obstacles that would need to be addressed to reach that goal.
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Affiliation(s)
- Mackenzie E Hofmann
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, USA
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Sidhpura N, Parsons LH. Endocannabinoid-mediated synaptic plasticity and addiction-related behavior. Neuropharmacology 2011; 61:1070-87. [PMID: 21669214 DOI: 10.1016/j.neuropharm.2011.05.034] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 05/26/2011] [Accepted: 05/29/2011] [Indexed: 01/20/2023]
Abstract
Endogenous cannabinoids (eCBs) are retrograde messengers that provide feedback inhibition of both excitatory and inhibitory transmission in brain through the activation of presynaptic CB₁ receptors. Substantial evidence indicates that eCBs mediate various forms of short- and long-term plasticity in brain regions involved in the etiology of addiction. The present review provides an overview of the mechanisms through which eCBs mediate various forms of synaptic plasticity and discusses evidence that eCB-mediated plasticity is disrupted following exposure to a variety of abused substances that differ substantially in pharmacodynamic mechanism including alcohol, psychostimulants and cannabinoids. The possible involvement of dysregulated eCB signaling in maladaptive behaviors that evolve over long-term drug exposure is also discussed, with a particular focus on altered behavioral responses to drug exposure, deficient extinction of drug-related memories, increased drug craving and relapse, heightened stress sensitivity and persistent affective disruption (anxiety and depression).
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Affiliation(s)
- Nimish Sidhpura
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
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Morera-Herreras T, Ruiz-Ortega JA, Taupignon A, Baufreton J, Manuel I, Rodriguez-Puertas R, Ugedo L. Regulation of subthalamic neuron activity by endocannabinoids. Synapse 2010; 64:682-98. [PMID: 20336631 DOI: 10.1002/syn.20778] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
High levels of anandamide are located in the basal ganglia. The subthalamic nucleus (STN) is considered to be an important modulator of basal ganglia output. The present study aims at characterizing the modulation of the electrical activity of STN neurons by exogenous anandamide or endocannabinoids. Single-unit extracellular recordings in anesthetized rats and patch-clamp techniques in rat brain slices containing the STN were performed. Immunohistochemical assays were used. In vivo, anandamide administration produced two opposite effects (inhibition or stimulation) on STN neuron firing rates, depending of the precise location of the neuron within the nucleus. These effects were enhanced by prior inhibition of fatty acid amide hydrolase with URB597, but not by the inhibitor of carrier-mediated anandamide transport AM404. Rimonabant, a specific CB(1) receptor antagonist, also produced inhibition or stimulation of STN neuron activity when administered alone or after anandamide. These effects seem to be mediated by indirect mechanisms since: (1) STN neuron activity is not modified by the cannabinoid agonist Delta(9)-tetrahydrocannabinol (Delta(9)-THC) in vitro; (2) no depolarization-induced suppression of inhibition phenomena were observed; and (3) CB(1) receptor immunolabeling was not detected in the STN, but was abundant in areas which project efferents to this nucleus. Moreover, chemical lesion of the globus pallidus abolished the stimulatory effect of anandamide and microinfusion of anandamide into the prefrontal cortex led to inhibition of STN neuron activity. The present results show that endocannabinoids exert a tonic control on STN activity via receptors located outside the nucleus. These findings may contribute to enhance our understanding of the role of the endocannabinoid system in motor control.
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Affiliation(s)
- Teresa Morera-Herreras
- Department of Pharmacology, Faculty of Medicine, University of the Basque Country, E-48940 Leioa, Vizcaya, Spain
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29
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Functional, metabolic, and synaptic changes after seizures as potential targets for antiepileptic therapy. Epilepsy Behav 2010; 19:105-13. [PMID: 20705520 DOI: 10.1016/j.yebeh.2010.06.035] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 06/17/2010] [Indexed: 01/11/2023]
Abstract
Little is known about how the brain limits seizure duration and terminates seizures. Depending on severity and duration, a single seizure is followed by various functional, metabolic, and synaptic changes that may form targets for novel therapeutic strategies. It is long known that most seizures are followed by a period of postictal refractoriness during which the threshold for induction of additional seizures is increased. The endogenous anticonvulsant mechanisms involved in this phenomenon may be relevant for both spontaneous seizure arrest and increase of seizure threshold after seizure arrest. Postictal refractoriness has been extensively studied in various seizure and epilepsy models, including electrically and chemically induced seizures, kindling, and genetic animal models of epilepsy. During kindling development, two antagonistic processes occur simultaneously, one responsible for kindling-like events and the other for terminating ictus and postictal refractoriness. Frequently occurring seizures may lead to an accumulation of postictal refractoriness that may last weeks. The mechanisms involved in seizure termination and postictal refractoriness include changes in ionic microenvironment, in pH, and in various endogenous neuromodulators such as adenosine and neuropeptides. In animal models, the anticonvulsant efficacy of several antiepileptic drugs (AEDs) is increased during postictal refractoriness, which is a logical consequence of the interaction between endogenous anticonvulsant processes and the mechanism of AEDs. As discussed in this review, enhanced understanding of these endogenous processes may lead to novel targets for AED development.
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30
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Properties of cannabinoid-dependent long-term depression in the leech. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2010; 196:841-51. [PMID: 20803022 DOI: 10.1007/s00359-010-0566-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 08/02/2010] [Accepted: 08/03/2010] [Indexed: 12/15/2022]
Abstract
Previously, a cannabinoid-dependent form of long-term depression (LTD) was discovered at the polysynaptic connection between the touch mechanosensory neuron and the S interneuron (Li and Burrell in J Comp Physiol A 195:831-841, 2009). In the present study, the physiological properties of this cannabinoid-dependent LTD were examined. Increases in intracellular calcium in the S interneuron are necessary for this form of LTD in this circuit. Calcium signals contributing to cannabinoid-dependent LTD are mediated by voltage-dependent calcium channel and release of calcium from intracellular stores. Inositol triphosphate receptors, but not ryanodine receptors, appear to mediate this store-released calcium signal. Cannabinoid-dependent LTD also requires activation of metabotropic serotonin receptors, possibly a serotonin type 2-like receptor. Finally, this form of LTD involves the stimulation of nitric oxide synthase and a decrease in cyclic adenosine monophosphate signaling, both of which appeared to be downstream of cannabinoid receptor activation. Based on these findings, the cellular signaling mechanisms of cannabinoid-dependent LTD in the leech are remarkably similar to vertebrate forms of cannabinoid-dependent synaptic plasticity.
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Abstract
A fundamental property of neuronal networks in Ammon's horn is that each area comprises a single glutamatergic cell population and various types of GABAergic neurons. Here we describe an exception to this rule, in the form of granule cells that reside within the CA3 area and function as glutamatergic nonprincipal cells with distinct properties. CA3 granule cells in normal, healthy rats, similarly to dentate gyrus granule cells, coexpressed calbindin and the homeobox protein Prox1. However, CA3 granule cells were located outside of the dentate gyrus, often hundreds of micrometers from the hilar border, in the lucidum and radiatum layers. CA3 granule cells were present in numbers that were comparable to the rarer GABAergic neuronal subtypes, and their somato-dendritic morphology, intrinsic properties, and perforant path inputs were similar to those of dentate gyrus granule cells. CA3 granule cell axons displayed giant mossy fiber terminals with filopodial extensions, demonstrating that not all mossy fibers originate from the dentate gyrus. Somatic paired recordings revealed that CA3 granule cells innervated CA3 pyramidal and GABAergic cells similarly to conventional mossy fiber synapses. However, CA3 granule cells were distinct in the specific organization of their GABAergic inputs. They received GABAergic synapses from cholecystokinin-expressing mossy fiber-associated cells that did not innervate the dentate granule cell layer, and these synapses demonstrated unusually strong activity-dependent endocannabinoid-mediated inhibition of GABA release. These results indicate that granule cells in the CA3 constitute a glutamatergic, nonprincipal neuronal subtype that is integrated into the CA3 synaptic network.
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Bhaskaran MD, Smith BN. Effects of TRPV1 activation on synaptic excitation in the dentate gyrus of a mouse model of temporal lobe epilepsy. Exp Neurol 2010; 223:529-36. [PMID: 20144892 DOI: 10.1016/j.expneurol.2010.01.021] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 01/08/2010] [Accepted: 01/31/2010] [Indexed: 11/25/2022]
Abstract
Temporal lobe epilepsy (TLE) is a condition characterized by an imbalance between excitation and inhibition in the temporal lobe. Hallmarks of this change are axon sprouting and accompanying synaptic reorganization in the temporal lobe. Synthetic and endogenous cannabinoids have variable therapeutic potential in treating intractable temporal lobe epilepsy, in part because cannabinoid ligands can bind multiple receptor types. This study utilized in vitro electrophysiological methods to examine the effect of transient receptor potential vanilloid type 1 (TRPV1) activation in dentate gyrus granule cells in a murine model of TLE. Capsaicin, a selective TRPV1 agonist had no measurable effect on overall synaptic input to granule cells in control animals, but significantly enhanced spontaneous and miniature EPSC frequency in mice with TLE. Exogenous application of anandamide, an endogenous cannabinoid that acts at both TRPV1 and cannabinoid type 1 receptors (CB1R), also enhanced glutamate release in the presence of a CB1R antagonist. Anandamide reduced the EPSC frequency when TRPV1 were blocked with capsazepine. Western blot analysis of TRPV1 receptor indicated protein expression was significantly greater in the dentate gyrus of mice with TLE compared with control mice. This study indicates that a prominent cannabinoid agonist can increase excitatory circuit activity in the synaptically reorganized dentate gyrus of mice with TLE by activating TRPV1 receptors, and suggests caution in designing anticonvulsant therapy based on modulating the endocannabinoid system.
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Affiliation(s)
- Muthu D Bhaskaran
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118, USA
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Sang N, Zhang J, Chen C. Anandamide potentiation of miniature spontaneous excitatory synaptic transmission is mediated via IP3 pathway. Neurochem Int 2010; 56:590-6. [PMID: 20064571 DOI: 10.1016/j.neuint.2010.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 12/18/2009] [Accepted: 01/05/2010] [Indexed: 10/20/2022]
Abstract
Although arachidonoyl ethanolamide (AEA or anandamide) is the first identified endocannabinoid, its roles in synaptic signaling and neuronal survival are still controversial. Here we report that AEA induced a dose-dependent elevation of the frequency of miniature excitatory postsynaptic currents (mEPSCs) in mouse hippocampal neurons in culture. This potentiation was not blocked by SR141716 or AM251, selective cannabinoid receptor antagonists, indicating that the AEA elevation of mEPSCs is not mediated via the CB1 receptor. Similarly, capsazepine and iodoresiniferatoxin, selective vanilloid receptor antagonists, and ryanodine also failed to inhibit the effect of AEA on mEPSCs. However, 2-APB and Xestospongin C, IP3 inhibitors, significantly attenuated AEA-induced increase in hippocampal excitatory synaptic transmission. Application of 3-deoxy-3-fluoro-d-myo-inositol 1,4,5-trisphosphate enhanced the frequency of mEPSCs and occluded the effect of AEA on mEPSCs. Our results suggest that AEA-produced stimulatory effect on excitatory glutamatergic synaptic transmission is likely mediated via an IP3 pathway.
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Affiliation(s)
- Nan Sang
- College of Environment and Resource, Shanxi University, Taiyuan, Shanxi 030006, PR China.
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Straiker A, Mackie K. Cannabinoid signaling in inhibitory autaptic hippocampal neurons. Neuroscience 2009; 163:190-201. [PMID: 19501632 DOI: 10.1016/j.neuroscience.2009.06.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 06/01/2009] [Accepted: 06/03/2009] [Indexed: 01/04/2023]
Abstract
Depolarization-induced suppression of excitation and inhibition (DSE/DSI) appears to be an important form of short-term retrograde neuronal plasticity involving endocannabinoids (eCBs), the activation of presynaptic cannabinoid CB1 receptors, and the suppression of neurotransmitter release. Using murine autaptic hippocampal cultures, we have distinguished five populations of autaptic inhibitory neurons that exhibit differential cannabinoid responses, including three temporally distinct forms of DSI. One remaining population responded to cannabinoids but did not have DSI while a fifth had neither DSI nor cannabinoid responses. Of the two chief candidate eCBs, 2-AG reversibly inhibited inhibitory post synaptic currents (IPSCs) while anandamide did so irreversibly, the latter's action inconsistent with a role as a bona fide eCB mediator of DSI. The duration of depolarization necessary to elicit the two most prominent forms of DSI (effective dose (ED-50) approximately 210, approximately 280 ms) was far less than for autaptic DSE. However the nearly identical concentration response for 2-AG to inhibit excitatory postsynaptic currents (EPSCs) and IPSCs indicates that this difference is not due to differential cannabinoid receptor sensitivity. Interestingly, of the two populations exhibiting prominent DSI, one had a substantially faster recovery time course both after DSI and 2-AG, this despite being cultured under identical conditions. Several enzymes have been proposed to play a role in 2-AG breakdown, presumably determining the time course of DSI: fatty acid amide hydrolase (FAAH), cyclooxygenase-2 (COX-2), monoacyl glycerol lipase (MGL), and alpha/beta-hydrolase domains 6 and 12 (ABHD6 and ABHD12). We tested the impact on DSI duration by blockers of FAAH, COX-2, MGL and ABHD6. Notably, the population with slow DSI was regulated only by MGL, whereas the fast DSI population was regulated by both MGL and COX-2. This suggests that the faster DSI time course may occur as a result of the concerted action of multiple enzymes, which may represent a more general mechanism for regulation of the duration of different forms of DSI and DSE.
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Affiliation(s)
- A Straiker
- Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, Bloomington, IN 47405, USA.
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Berrout J, Isokawa M. Homeostatic and stimulus-induced coupling of the L-type Ca2+ channel to the ryanodine receptor in the hippocampal neuron in slices. Cell Calcium 2009; 46:30-8. [PMID: 19411104 DOI: 10.1016/j.ceca.2009.03.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Revised: 02/20/2009] [Accepted: 03/31/2009] [Indexed: 11/30/2022]
Abstract
Activity-dependent increase in cytosolic calcium ([Ca(2+)](i)) is a prerequisite for many neuronal functions. We previously reported a strong direct depolarization, independent of glutamate receptors, effectively caused a release of Ca(2+) from ryanodine-sensitive stores and induced the synthesis of endogenous cannabinoids (eCBs) and eCB-mediated responses. However, the cellular mechanism that initiated the depolarization-induced Ca(2+)-release is not completely understood. In the present study, we optically recorded [Ca(2+)](i) from CA1 pyramidal neurons in the hippocampal slice and directly monitored miniature Ca(2+) activities and depolarization-induced Ca(2+) signals in order to determine the source(s) and properties of [Ca(2+)](i)-dynamics that could lead to a release of Ca(2+) from the ryanodine receptor. In the absence of depolarizing stimuli, spontaneously occurring miniature Ca(2+) events were detected from a group of hippocampal neurons. This miniature Ca(2+) event persisted in the nominal Ca(2+)-containing artificial cerebrospinal fluid (ACSF), and increased in frequency in response to the bath-application of caffeine and KCl. In contrast, nimodipine, the antagonist of the L-type Ca(2+) channel (LTCC), a high concentration of ryanodine, the antagonist of the ryanodine receptor (RyR), and thapsigargin (TG) reduced the occurrence of the miniature Ca(2+) events. When a brief puff-application of KCl was given locally to the soma of individual neurons in the presence of glutamate receptor antagonists, these neurons generated a transient increase in the [Ca(2+)](i) in the dendrosomal region. This [Ca(2+)](i)-transient was sensitive to nimodipine, TG, and ryanodine suggesting that the [Ca(2+)](i)-transient was caused primarily by the LTCC-mediated Ca(2+)-influx and a release of Ca(2+) from RyR. We observed little contribution from N- or P/Q-type Ca(2+) channels. The coupling between LTCC and RyR was direct and independent of synaptic activities. Immunohistochemical study revealed a cellular localization of LTCC and RyR in a juxtaposed configuration in the proximal dendrites and soma. We conclude in the hippocampal CA1 neuron that: (1) homeostatic fluctuation of the resting membrane potential may be sufficient to initiate functional coupling between LTCC and RyR; (2) the juxtaposed localization of LTCC and RyR has anatomical advantage of synchronizing a Ca(2+)-release from RyR upon the opening of LTCC; and (3) the synchronized Ca(2+)-release from RyR occurs immediately after the activation of LTCC and determines the peak amplitude of depolarization-induced global increase in dendrosomal [Ca(2+)](i).
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Affiliation(s)
- Jonathan Berrout
- Department of Biological Sciences, The University of Texas at Brownsville, 80 Fort Brown, Brownsville, TX 78520, USA
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36
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Fu LW, Longhurst JC. Electroacupuncture modulates vlPAG release of GABA through presynaptic cannabinoid CB1 receptors. J Appl Physiol (1985) 2009; 106:1800-9. [PMID: 19359606 DOI: 10.1152/japplphysiol.91648.2008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies have demonstrated that electroacupuncture (EA) attenuates sympathoexcitatory reflex responses by activating a long-loop pathway involving the hypothalamic arcuate nucleus (ARC), midbrain ventrolateral periaqueductal gray (vlPAG), and rostral ventrolateral medulla (rVLM). Neurons in the ARC provide excitatory input to the vlPAG, whereas the vlPAG inhibits neuronal activity in the rVLM. gamma-Aminobutyric acid (GABA) and glutamate (Glu) have been identified in the vlPAG. Endocannabinoids (ECs), acting as atypical neurotransmitters, inhibit the release of both neurotransmitters in the hypothalamus and midbrain through a presynaptic cannabinoid type 1 (CB(1)) receptor mechanism. The EC system has been observed in the dorsal but not in the vlPAG. Since it is uncertain whether ECs influence GABA and Glu in the vlPAG, the present study tested the hypothesis that EA modulates the release of these neurotransmitters in the vlPAG through a presynaptic CB(1) receptor mechanism. We measured the release of GABA and Glu simultaneously by using HPLC to assess samples collected with microdialysis probes inserted unilaterally into the vlPAG of intact anesthetized rats. Twenty-eight min of EA (2 Hz, 2-4 mA, 0.5 ms) at the P5-6 acupoints reduced the release of GABA by 39% during EA and by 44% 15 min after EA. Thirty-five minutes after EA, GABA concentrations returned to pre-EA levels. In contrast, sham EA did not change the vlPAG GABA concentration. Blockade of CB(1) receptors with AM251, a selective CB(1) receptor antagonist, reversed the EA-modulated changes in GABA concentration, whereas microinjection of vehicle into the vlPAG did not alter EA-modulated GABA changes. In addition, we observed no changes in the vlPAG Glu concentrations during EA, although the baseline concentration of Glu was much higher than that of GABA (3,541 +/- 373 vs. 33.8 +/- 8.7 nM, Glu vs. GABA). These results suggest that EA modulates the sympathoexcitatory reflex responses by decreasing the release of GABA, but not Glu, in the vlPAG, most likely through a presynaptic CB(1) receptor mechanism.
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Affiliation(s)
- Liang-Wu Fu
- Department of Medicine, University of California, Irvine, CA 92697, USA.
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37
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Kano M, Ohno-Shosaku T, Hashimotodani Y, Uchigashima M, Watanabe M. Endocannabinoid-mediated control of synaptic transmission. Physiol Rev 2009; 89:309-80. [PMID: 19126760 DOI: 10.1152/physrev.00019.2008] [Citation(s) in RCA: 1048] [Impact Index Per Article: 69.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The discovery of cannabinoid receptors and subsequent identification of their endogenous ligands (endocannabinoids) in early 1990s have greatly accelerated research on cannabinoid actions in the brain. Then, the discovery in 2001 that endocannabinoids mediate retrograde synaptic signaling has opened up a new era for cannabinoid research and also established a new concept how diffusible messengers modulate synaptic efficacy and neural activity. The last 7 years have witnessed remarkable advances in our understanding of the endocannabinoid system. It is now well accepted that endocannabinoids are released from postsynaptic neurons, activate presynaptic cannabinoid CB(1) receptors, and cause transient and long-lasting reduction of neurotransmitter release. In this review, we aim to integrate our current understanding of functions of the endocannabinoid system, especially focusing on the control of synaptic transmission in the brain. We summarize recent electrophysiological studies carried out on synapses of various brain regions and discuss how synaptic transmission is regulated by endocannabinoid signaling. Then we refer to recent anatomical studies on subcellular distribution of the molecules involved in endocannabinoid signaling and discuss how these signaling molecules are arranged around synapses. In addition, we make a brief overview of studies on cannabinoid receptors and their intracellular signaling, biochemical studies on endocannabinoid metabolism, and behavioral studies on the roles of the endocannabinoid system in various aspects of neural functions.
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Affiliation(s)
- Masanobu Kano
- Department of Neurophysiology, The University of Tokyo, Tokyo, Japan.
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Hofmann ME, Nahir B, Frazier CJ. Excitatory afferents to CA3 pyramidal cells display differential sensitivity to CB1 dependent inhibition of synaptic transmission. Neuropharmacology 2008; 55:1140-6. [PMID: 18675282 DOI: 10.1016/j.neuropharm.2008.07.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 06/25/2008] [Accepted: 07/07/2008] [Indexed: 11/27/2022]
Abstract
Recent advances in immunohistochemical techniques have, contrary to earlier reports, positively identified CB1 receptors on glutamatergic terminals in the hippocampus. Further work has implicated these receptors in modulation of susceptibility to kainic acid induced seizures. Based on these results, the current study was designed to test the hypothesis that both exogenous and endogenous cannabinoids can selectively modulate glutamatergic afferents to CA3 pyramidal cells, and that such modulation is mediated by cannabinoid type 1 (CB1) receptors. Towards that end we employed either conventional or two-photon guided minimal stimulation techniques to isolate mossy fiber and/or associational/commissural (A/C) inputs to CA3 pyramidal cells. We report that bath application of WIN55,212-2 selectively inhibits minimally evoked A/C inputs to CA3 pyramidal cells, without significantly altering simultaneously recorded mossy fiber inputs. Further, we find that WIN55,212-2 mediated inhibition of A/C inputs is completely blocked by the CB1 selective antagonist AM-251 and absent in CB1(-/-) animals, suggesting a dependence on CB1 receptors. Finally, we demonstrate that depolarization of CA3 pyramidal cells leads to calcium dependent release of endogenous cannabinoids that transiently inhibit A/C mediated responses, and that this effect is also sensitive to both AM-251 and the muscarinic acetylcholine receptor antagonist atropine. To our knowledge this represents the first demonstration of depolarization induced suppression of excitation in area CA3 of the hippocampus. Collectively, these results provide new information relevant to developing a thorough understanding of how ECs modulate excitatory transmission in an area that is both essential for the acquisition of new memories and intimately involved in epileptogenesis.
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Affiliation(s)
- Mackenzie E Hofmann
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, 1600 S.W. Archer Road, Gainesville, FL 32610, USA
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Sokal DM, Benetti C, Girlanda E, Large CH. The CB1 receptor antagonist, SR141716A, prevents high-frequency stimulation-induced reduction of feedback inhibition in the rat dentate gyrus following perforant path stimulation in vivo. Brain Res 2008; 1223:50-8. [PMID: 18599027 DOI: 10.1016/j.brainres.2008.05.065] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 05/27/2008] [Accepted: 05/28/2008] [Indexed: 02/08/2023]
Abstract
Endocannabinoids acting through CB(1) receptors are thought to regulate GABAergic and glutamatergic neurotransmission and may modulate long-term potentiation (LTP). High-frequency stimulation (HFS) of the medial perforant path to induce LTP was studied in the dentate gyrus with or without the selective CB(1) receptor antagonist, SR141716A in isoflurane-anaesthetised rats. HFS significantly increased the slope of the field excitatory post-synaptic potential (fEPSP) and the amplitude of the population spike (PS; P<0.001 in each case; n=6). Following administration of SR141716A, HFS no longer increased fEPSP slope, whereas PS amplitude potentiation remained significant (P<0.0001; n=6). Paired-stimuli revealed that HFS significantly reduced inhibition observed at intervals of 10 ms (P<0.01; n=6), and produced a leftward shift of the interval-inhibition curve (P<0.05; n=6). Following administration of SR141716A, HFS no longer reduced inhibition at the 10 ms interval, but a leftward shift in the interval-inhibition curve was still observed (P<0.05, n=6). These results indicate that LTP in the dentate gyrus reduces local circuit inhibition, consistent with a reduction of GABA release and/or duration of the post-synaptic GABA-receptor mediated response. Selective effects of SR141716A on the degree, but not the timecourse, of paired-pulse inhibition suggest that the reduction in GABA release following LTP induction is due to CB(1) activation. Results also suggest that CB(1) receptors contribute to HFS-induced potentiation of the fEPSP, but not to the mechanism underlying potentiation of PS amplitude. We suggest that CB(1) activation during HFS of the medial perforant path increases glutamate release from perforant path synapses, but inhibits release of GABA from local circuit interneurons.
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Affiliation(s)
- David M Sokal
- Department of Biology, Psychiatry CEDD, GlaxoSmithKline Medicines Research Centre, Via A. Fleming 4, Verona, Italy.
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López-Moreno JA, González-Cuevas G, Moreno G, Navarro M. The pharmacology of the endocannabinoid system: functional and structural interactions with other neurotransmitter systems and their repercussions in behavioral addiction. Addict Biol 2008; 13:160-87. [PMID: 18422831 DOI: 10.1111/j.1369-1600.2008.00105.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Addiction is a chronic, recurring and complex disorder. It is characterized by anomalous behaviors that are linked to permanent or long-lasting neurobiological alterations. Furthermore, the endocannabinoid system has a crucial role in mediating neurotransmitter release as one of the main neuromodulators of the mammalian central nervous system. The purpose of the present review is to instruct readers about the functional and structural interactions between the endocannabinoid system and the main neurotransmitter systems of the central nervous system in the context of drug addiction. With this aim, we have systematically reviewed the main findings of most of the existing literature that explores cross-talk in the five brain areas that are most traditionally implicated in addiction: amygdala, prefrontal cortex, nucleus accumbens, hippocampus and ventral tegmental area (VTA). The neurotransmission systems influenced by the pharmacology of the endocannabinoid system in these brain areas, which are reviewed here, are gamma-aminobutyric acid (GABA), glutamate, the main biogenic amines (dopamine, noradrenaline and serotonin), acetylcholine and opioids. We show that all of these neurotransmitter systems can be modulated differentially in each brain area by the activation or deactivation of cannabinoid CB1 brain receptors. Specifically, most of the studies relate to the hippocampus and nucleus accumbens. Moreover, the neurotransmitter with the fewest number of related studies is acetylcholine (excepting in the hippocampus), whereas there is a large number that evaluates GABA, glutamate and dopamine. Finally, we propose a possible interpretation of the role of the endocannabinoid system in the phenomenon of addiction.
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Affiliation(s)
- José Antonio López-Moreno
- Department of Psychobiology, Faculty of Psychology, Campus de Somosaguas, Complutense University of Madrid, Spain.
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41
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Abstract
Modulation of neurotransmitter release by G-protein-coupled receptors (GPCRs) is a prominent presynaptic mechanism for regulation of synaptic transmission. Activation of GPCRs located at the presynaptic terminal can decrease the probability of neurotransmitter release. This presynaptic depression involves activation of Gi/o-type G-proteins that mediate different inhibitory mechanisms, including inhibition of voltage-gated calcium channels, activation of potassium channels, and direct inhibition of the vesicle fusion process. A variety of neurotransmitters and modulatory agents can activate GPCRs that produce presynaptic depression. Among these are lipid metabolites that serve as agonists for GPCRs. The discovery of endocannabinoids and their cognate receptors, including the CB1 receptor, has stimulated intense investigation into the neurophysiological roles of these lipid metabolites. It is now clear that presynaptic depression is the major physiological role for the CB1 receptor. Endocannabinoids activate this receptor mainly via a retrograde signaling process in which these compounds are synthesized in and released from postsynaptic neuronal elements, and travel back to the presynaptic terminal to act on the CB1 receptor. This retrograde endocannabinoid modulation has been implicated in short-term synaptic depression, including suppression of excitatory or inhibitory transmission induced by postsynaptic depolarization and transient synaptic depression induced by activation of postsynaptic GPCRs during agonist treatment or synaptic activation. Endocannabinoids and the CB1 receptor also play a key role in one form of long-term synaptic depression (LTD) that involves a longlasting decrease in neurotransmitter release.
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MESH Headings
- Animals
- Behavior/drug effects
- Cannabinoid Receptor Modulators/metabolism
- Cannabinoid Receptor Modulators/physiology
- Cannabinoids/metabolism
- Cannabinoids/pharmacology
- Cannabinoids/toxicity
- Endocannabinoids
- Humans
- Long-Term Potentiation/drug effects
- Long-Term Potentiation/physiology
- Neuronal Plasticity/drug effects
- Neurotransmitter Uptake Inhibitors/pharmacology
- Receptor, Cannabinoid, CB1/drug effects
- Receptor, Cannabinoid, CB1/metabolism
- Receptor, Cannabinoid, CB1/physiology
- Receptors, Cannabinoid/drug effects
- Receptors, Cannabinoid/metabolism
- Receptors, Cannabinoid/physiology
- Receptors, Presynaptic/drug effects
- Receptors, Presynaptic/metabolism
- Receptors, Presynaptic/physiology
- Signal Transduction/drug effects
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Affiliation(s)
- David M Lovinger
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Bethesda, MD 20892-9411, USA.
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42
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Chiu CQ, Castillo PE. Input-specific plasticity at excitatory synapses mediated by endocannabinoids in the dentate gyrus. Neuropharmacology 2007; 54:68-78. [PMID: 17706254 PMCID: PMC2225485 DOI: 10.1016/j.neuropharm.2007.06.026] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2007] [Revised: 06/04/2007] [Accepted: 06/21/2007] [Indexed: 11/23/2022]
Abstract
Endocannabinoids (eCBs) mediate transient and long-lasting synaptic plasticity in several brain structures. In the dentate gyrus, activation of the type 1 cannabinoid receptor (CB1R) by exogenous ligands reportedly depresses excitatory synaptic transmission. However, direct evidence of eCB signaling at excitatory synapses in this region has been lacking. Here, we demonstrate that eCB release can be induced by a brief postsynaptic depolarization of dentate granule cells (DGCs), which potently and transiently suppresses glutamatergic inputs from mossy cell interneurons (MCs) but not from entorhinal cortex via the lateral and medial perforant paths. This input-specific depolarization-induced suppression of excitation (DSE) is calcium-dependent and can be modulated by agonists of cholinergic and group I metabotropic glutamate receptors. Inhibiting the synthesis of 2-arachidonoyl glycerol (2-AG), one of the most abundant eCBs in the brain, by diacyglycerol lipase (DGL) does not abolish DSE. Moreover, preventing the breakdown of anandamide, the other main eCB, does not potentiate DSE. Thus, eCB signaling underlying DSE in the dentate does not require DGL activity and is unlikely to be mediated by anandamide. Finally, we find that manipulations known to induce eCB-LTD at other central synapses do not trigger LTD at MCF-DGC synapses.
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Affiliation(s)
| | - Pablo E. Castillo
- *Correspondence should be addressed to P.E.C. (): Pablo E. Castillo, Dominick P. Purpura Dept. of Neuroscience, Albert Einstein College of Medicine, Kennedy Center Rm. 703, 1410 Pelham Parkway South, Bronx, NY 10461, (718) 430 3263, (718) 430 8821
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43
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Maćkowiak M, Chocyk A, Markowicz-Kula K, Wędzony K. Acute activation of CB1 cannabinoid receptors transiently decreases PSA-NCAM expression in the dentate gyrus of the rat hippocampus. Brain Res 2007; 1148:43-52. [DOI: 10.1016/j.brainres.2007.02.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 02/02/2007] [Accepted: 02/08/2007] [Indexed: 12/13/2022]
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44
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Abstract
Recent years have produced rapid and enormous growth in our understanding of endocannabinoid-mediated signaling in the CNS. While much of the recent progress has focused on other areas of the brain, a significant body of evidence has developed that indicates the presence of a robust system for endocannabinoid-mediated signaling in the dentate gyrus. This chapter will provide an overview of our current understanding of that system based on available anatomical and physiological data.
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Affiliation(s)
- Charles J Frazier
- Department of Pharmacodynamics, University of Florida, College of Pharmacy, Gainesville, FL 32610, USA.
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45
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Hofmann ME, Nahir B, Frazier CJ. Endocannabinoid-Mediated Depolarization-Induced Suppression of Inhibition in Hilar Mossy Cells of the Rat Dentate Gyrus. J Neurophysiol 2006; 96:2501-12. [PMID: 16807350 DOI: 10.1152/jn.00310.2006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hilar mossy cells represent a unique population of local circuit neurons in the hippocampus and dentate gyrus. Here we use electrophysiological techniques in acute preparations of hippocampal slices to demonstrate that depolarization of a single hilar mossy cell can produce robust inhibition of local GABAergic afferents. This depolarization-induced suppression of inhibition (DSI) can be observed as a transient reduction in frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) or as a transient reduction in amplitude of evoked IPSCs (eIPSCs). We find that DSI of eIPSCs as observed in hilar mossy cells is enhanced by activation of muscarinic acetylcholine receptors, blocked by chelation of postsynaptic calcium, and critically dependent on retrograde activation of presynaptic cannabinoid type 1 (CB1) receptors. We further report that activation of CB1 receptors on GABAergic afferents to hilar mossy cells (by either endogenous or exogenous agonists) preferentially inhibits calcium-dependent exocytosis and that endocannabinoid-dependent retrograde signaling in this system is subject to tight spatial constraints.
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Affiliation(s)
- Mackenzie E Hofmann
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, JHMHC Box 100487, 1600 S.W. Archer Road, Gainesville, FL 32610, USA
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46
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Abstract
Changes in synaptic efficacy are thought to be crucial to experience-dependent modifications of neural function. The diversity of mechanisms underlying these changes is far greater than previously expected. In the last five years, a new class of use-dependent synaptic plasticity that requires retrograde signaling by endocannabinoids (eCB) and presynaptic CB1 receptor activation has been identified in several brain structures. eCB-mediated plasticity encompasses many forms of transient and long-lasting synaptic depression and is found at both excitatory and inhibitory synapses. In addition, eCBs can modify the inducibility of non-eCB-mediated forms of plasticity. Thus, the eCB system is emerging as a major player in synaptic plasticity. Given the wide distribution of CB1 receptors in the CNS, the list of brain structures and synapses expressing eCB-mediated plasticity is likely to expand.
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Affiliation(s)
- Vivien Chevaleyre
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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47
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Sang N, Zhang J, Chen C. PGE2 glycerol ester, a COX-2 oxidative metabolite of 2-arachidonoyl glycerol, modulates inhibitory synaptic transmission in mouse hippocampal neurons. J Physiol 2006; 572:735-45. [PMID: 16484297 PMCID: PMC1780008 DOI: 10.1113/jphysiol.2006.105569] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The oxygenation of endogenous cannabinoids (eCBs) 2-arachidonoyl glycerol (2-AG) and arachidonoyl ethanolamide by cyclooxygenase-2 (COX-2) produces novel types of prostanoids: prostaglandin glycerol esters (PG-Gs) and prostaglandin ethanolamides (PG-EAs). However, the physiological function of COX-2 oxidative metabolites of eCBs is still unclear. Here we demonstrate that PGE2-G, a COX-2 oxidative metabolite of 2-AG, induced a concentration-dependent increase in the frequency ofminiature inhibitory postsynaptic currents (mIPSCs) in primary cultured hippocampal neurons, an effect opposite to that of 2-AG. This increase was not inhibited by SR141716, a CB1 receptor antagonist, but was attenuated by an IP3 or MAPK inhibitor. In addition, we also examined the effects of other prostanoids derived from COX-2 oxygenation of eCBs on mIPSCs. PGD2-G, PGF2alpha-G and PGD2-EA, but not PGE2-EA or PGF2alpha-EA, also increased the frequency of mIPSCs. The eCB-derived prostanoid-induced responses appeared to be different from those of corresponding arachidonic acid-derived prostanoids, implying that these effects are not mediated via known prostanoid receptors. We further discovered that the inhibition of COX-2 activity reduced inhibitory synaptic activity and augmented depolarization-induced suppression of inhibition (DSI), whereas the enhancement of COX-2 augmented the synaptic transmission and abolished DSI. Our results, which show that COX-2 oxidative metabolites of eCBs exert opposite effects to their parent molecules on inhibitory synaptic transmission, suggest that alterations in COX-2 activity will have significant impact on endocannabinoid signalling in hippocampal synaptic activity.
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Affiliation(s)
- Nan Sang
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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48
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Isokawa M, Alger BE. Ryanodine Receptor Regulates Endogenous Cannabinoid Mobilization in the Hippocampus. J Neurophysiol 2006; 95:3001-11. [PMID: 16467427 DOI: 10.1152/jn.00975.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endogenous cannabinoids (eCBs) are produced and mobilized in a cytosolic calcium ([Ca2+]i)–dependent manner, and they regulate excitatory and inhibitory neurotransmitter release by acting as retrograde messengers. An indirect but real-time bioassay for this process on GABAergic transmission is DSI (depolarization-induced suppression of inhibition). The magnitude of DSI correlates linearly with depolarization-induced increase of [Ca2+]ithat is thought to be initiated by Ca2+influx through voltage-gated Ca2+channels. However, the identity of Ca2+sources involved in eCB mobilization in DSI remains undetermined. Here we show that, in CA1 pyramidal cells, DSI-inducing depolarizing voltage steps caused Ca2+-induced Ca2+release (CICR) by activating the ryanodine receptor (RyR) Ca2+-release channel. CICR was reduced, and the remaining increase in [Ca2+]iwas less effective in generating DSI, when the RyR antagonists, ryanodine or ruthenium red, were applied intracellularly, or the Ca2+stores were depleted by the Ca2+-ATPase inhibitors, cyclopiazonic acid or thapsigargin. The CICR-dependent effects were most prominent in cultured or immature acute slices, but were also detectable in slices from adult tissue. Thus we suggest that voltage-gated Ca2+entry raises local [Ca2+]isufficiently to activate nearby RyRs and that the resulting CICR plays a critical role in initiating eCB mobilization. RyR may be a key molecule for the depolarization-induced production of eCBs that inhibit GABA release in the hippocampus.
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Affiliation(s)
- Masako Isokawa
- Department of Physiology, University of Maryland, Baltimore, Maryland, USA.
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49
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Straiker A, Mackie K. Cannabinoids, electrophysiology, and retrograde messengers: challenges for the next 5 years. AAPS JOURNAL 2006; 8:E272-6. [PMID: 16796377 PMCID: PMC3231565 DOI: 10.1007/bf02854897] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Most of the behavioral effects of cannabis and its active ingredients, the cannabinoids (delta9THC being the most abundant of these), appear to be mediated by cannabinoid receptors. Endogenous cannabinoids (endocannabinoids) are lipid mediators that activate these same cannabinoid receptors. Elegant work from several laboratories over the past 5 years has established that endocannabinoids, possibly acting as retrograde messengers, mediate several forms of neuronal plasticity. Endocannabinoid-mediated neuronal plasticity is common, apparently occurring at all neurons that express cannabinoid receptors. Thus, it is likely that delta9THC produces its effects by interacting with endocannabinoid-mediated neuronal plasticity, though whether it does so cooperatively or antagonistically remains an open question. In this review we will briefly discuss the work establishing endocannabinoids as mediators of neuronal plasticity and then present evidence that a major effect of delta9THC may be to antagonize the actions of endocannabinoids.
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Affiliation(s)
- Alex Straiker
- />Department of Anesthesiology, University, of Washington School of Medicine, Seattle, WA
| | - Ken Mackie
- />Department of Anesthesiology, University, of Washington School of Medicine, Seattle, WA
- />Department of Physiology and Biophysics, University of Washington School of Medicine, 1959 NE Pacific St, 98195-6540 Seattle, WA
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50
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Jo YH, Chen YJJ, Chua SC, Talmage DA, Role LW. Integration of endocannabinoid and leptin signaling in an appetite-related neural circuit. Neuron 2006; 48:1055-66. [PMID: 16364907 PMCID: PMC2280039 DOI: 10.1016/j.neuron.2005.10.021] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Revised: 07/22/2005] [Accepted: 10/05/2005] [Indexed: 12/18/2022]
Abstract
Recently developed therapeutics for obesity, targeted against cannabinoid receptors, result in decreased appetite and sustained weight loss. Prior studies have demonstrated CB1 receptors (CB1Rs) and leptin modulation of cannabinoid synthesis in hypothalamic neurons. Here, we show that depolarization of perifornical lateral hypothalamus (LH) neurons elicits a CB1R-mediated suppression of inhibition in local circuits thought to be involved in appetite and "natural reward." The depolarization-induced decrease in inhibitory tone to LH neurons is blocked by leptin. Leptin inhibits voltage-gated calcium channels in LH neurons via the activation of janus kinase 2 (JAK2) and of mitogen-activated protein kinase (MAPK). Leptin-deficient mice are characterized by both an increase in steady-state voltage-gated calcium currents in LH neurons and a CB1R-mediated depolarization-induced suppression of inhibition that is 6-fold longer than that in littermate controls. Our data provide direct electrophysiological support for the involvement of endocannabinoids and leptin as modulators of hypothalamic circuits underlying motivational aspects of feeding behavior.
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Affiliation(s)
- Young-Hwan Jo
- Department of Pathology and Cell Biology, Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
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