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Fontaine CJ, Gräfe EL, Pinar C, Bonilla-Del Río I, Grandes P, Christie BR. Endocannabinoid receptors contribute significantly to multiple forms of long-term depression in the rat dentate gyrus. LEARNING & MEMORY (COLD SPRING HARBOR, N.Y.) 2020; 27:380-389. [PMID: 32817304 PMCID: PMC7433656 DOI: 10.1101/lm.050666.119] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/02/2020] [Indexed: 12/12/2022]
Abstract
Cannabinoid receptors are widely expressed throughout the hippocampal formation, but are particularly dense in the dentate gyrus (DG) subregion. We, and others, have shown in mice that cannabinoid type 1 receptors (CB1Rs) are involved in a long-term depression (LTD) that can be induced by prolonged 10 Hz stimulation of the medial perforant path (MPP)-granule cell synaptic input to the DG. Here, we extend this work to examine the involvement of CB1Rs in other common forms of LTD in the hippocampus of juvenile male and female Sprague–Dawley rats (Rattus norvegicus). We found, as in mice, that prolonged 10 Hz stimulation (6000 pulses) could reliably induce a form of LTD that was dependent upon CB1R activation. In addition, we also discovered a role for both CB1R and mGluR proteins in LTD induced with 1 Hz low-frequency stimulation (1 Hz-LTD; 900 pulses) and in LTD induced by bath application of the group I mGluR agonist (RS)-3,5-Dihydroxyphenylglycine (DHPG; DHPG-LTD). This study elucidates an essential role for endocannabinoid receptors in a number of forms of LTD in the rat DG, and identifies a novel role for CB1Rs as potential therapeutic targets for conditions that involve impaired LTD in the DG.
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Affiliation(s)
- Christine J Fontaine
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Erin L Gräfe
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Cristina Pinar
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - Itziar Bonilla-Del Río
- 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
| | - Pedro Grandes
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada.,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
| | - Brian R Christie
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada.,Island Medical Program and Department of Cellular and Physiological Sciences, University of British Columbia, Victoria, British Columbia, USA
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Atwood BK, Lovinger DM, Mathur BN. Presynaptic long-term depression mediated by Gi/o-coupled receptors. Trends Neurosci 2014; 37:663-73. [PMID: 25160683 DOI: 10.1016/j.tins.2014.07.010] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 07/09/2014] [Accepted: 07/25/2014] [Indexed: 01/20/2023]
Abstract
Long-term depression (LTD) of the efficacy of synaptic transmission is now recognized as an important mechanism for the regulation of information storage and the control of actions, as well as for synapse, neuron, and circuit development. Studies of LTD mechanisms have focused mainly on postsynaptic AMPA-type glutamate receptor trafficking. However, the focus has now expanded to include presynaptically expressed plasticity, the predominant form being initiated by presynaptically expressed Gi/o-coupled metabotropic receptor (Gi/o-GPCR) activation. Several forms of LTD involving activation of different presynaptic Gi/o-GPCRs as a 'common pathway' are described. We review here the literature on presynaptic Gi/o-GPCR-mediated LTD, discuss known mechanisms, gaps in our knowledge, and evaluate whether all Gi/o-GPCRs are capable of inducing presynaptic LTD.
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Affiliation(s)
- Brady K Atwood
- Section on Synaptic Pharmacology, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, US National Institutes of Health, 5625 Fishers Lane, MSC 9411, Bethesda, MD 20852-9411, USA
| | - David M Lovinger
- Section on Synaptic Pharmacology, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, US National Institutes of Health, 5625 Fishers Lane, MSC 9411, Bethesda, MD 20852-9411, USA
| | - Brian N Mathur
- Department of Pharmacology, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
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Unusual increase in lumbar network excitability of the rat spinal cord evoked by the PARP-1 inhibitor PJ-34 through inhibition of glutamate uptake. Neuropharmacology 2012; 63:415-26. [PMID: 22561282 DOI: 10.1016/j.neuropharm.2012.04.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 04/11/2012] [Accepted: 04/16/2012] [Indexed: 11/21/2022]
Abstract
Overactivity of poly(ADP-ribose) polymerase enzyme 1 (PARP-1) is suggested to be a major contributor to neuronal damage following brain or spinal cord injury, and has led to study the PARP-1 inhibitor 2-(dimethylamino)-N-(5,6-dihydro-6-oxophenanthridin-2yl)acetamide (PJ-34) as a neuroprotective agent. Unexpectedly, electrophysiological recording from the neonatal rat spinal cord in vitro showed that, under control conditions, 1-60 μM PJ-34 per se strongly increased spontaneous network discharges occurring synchronously on ventral roots, persisting for 24 h even after PJ-34 washout. The PARP-1 inhibitor PHE had no similar effect. The action by PJ-34 was reversibly suppressed by glutamate ionotropic receptor blockers and remained after applying strychnine and bicuculline. Fictive locomotion evoked by neurochemicals or by dorsal root stimulation was present 24 h after PJ-34 application. In accordance with this observation, lumbar neurons and glia were undamaged. Neurochemical experiments showed that PJ-34 produced up to 33% inhibition of synaptosomal glutamate uptake with no effect on GABA uptake. In keeping with this result, the glutamate uptake blocker TBOA (5 μM) induced long-lasting synchronous discharges without suppressing the ability to produce fictive locomotion after 24 h. The novel inhibition of glutamate uptake by PJ-34 suggested that this effect may compound tests for its neuroprotective activity which cannot be merely attributed to PARP-1 block. Furthermore, the current data indicate that the neonatal rat spinal cord could withstand a strong, long-lasting rise in network excitability without compromising locomotor pattern generation or circuit structure in contrast with the damage to brain circuits known to be readily produced by persistent seizures.
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Piccolini V, Cerri S, Romanelli E, Bernocchi G. Interactions of neurotransmitter systems during postnatal development of the rat hippocampal formation: Effects of cisplatin. Exp Neurol 2012; 234:239-52. [DOI: 10.1016/j.expneurol.2011.12.044] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 12/21/2011] [Accepted: 12/25/2011] [Indexed: 01/14/2023]
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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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