title: Endocannabinoid-mediated rescue of striatal LTD and motor deficits in Parkinson's disease models.
abstract: The striatum is a major forebrain nucleus that integrates cortical and thalamic afferents and forms the input nucleus of the basal ganglia. Striatal projection neurons target the substantia nigra pars reticulata (direct pathway) or the lateral globus pallidus (indirect pathway). Imbalances between neural activity in these two pathways have been proposed to underlie the profound motor deficits observed in Parkinson's disease and Huntington's disease. However, little is known about differences in cellular and synaptic properties in these circuits. Indeed, current hypotheses suggest that these cells express similar forms of synaptic plasticity. Here we show that excitatory synapses onto indirect-pathway medium spiny neurons (MSNs) exhibit higher release probability and larger N-methyl-d-aspartate receptor currents than direct-pathway synapses. Moreover, indirect-pathway MSNs selectively express endocannabinoid-mediated long-term depression (eCB-LTD), which requires dopamine D2 receptor activation. In models of Parkinson's disease, indirect-pathway eCB-LTD is absent but is rescued by a D2 receptor agonist or inhibitors of endocannabinoid degradation. Administration of these drugs together in vivo reduces parkinsonian motor deficits, suggesting that endocannabinoid-mediated depression of indirect-pathway synapses has a critical role in the control of movement. These findings have implications for understanding the normal functions of the basal ganglia, and also suggest approaches for the development of therapeutic drugs for the treatment of striatal-based brain disorders.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Nancy Pritzker Laboratory, Stanford University Medical School, Palo Alto, California 94305, USA.
authors.forename: Anatol C
authors.initials: AC
authors.lastname: Kreitzer
authors.forename: Robert C
authors.initials: RC
authors.lastname: Malenka
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D048588:Benzoxazines; D063385:Cannabinoid Receptor Modulators / Q000378:metabolism*; D002219:Carbamates / Q000494:pharmacology; D004195:Disease Models, Animal; D004298:Dopamine / Q000172:deficiency / Q000378:metabolism; D065127:Dopamine D2 Receptor Antagonists; D063388:Endocannabinoids; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D036881:Long-Term Synaptic Depression / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D017072:Neostriatum / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D016627:Oxidopamine / Q000494:pharmacology; D010300:Parkinson Disease / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology; D011597:Psychomotor Performance / Q000502:physiology*; D011720:Pyrazoles / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012110:Reserpine / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000378:metabolism
chemical_list: D001549:Benzamides; D048588:Benzoxazines; D063385:Cannabinoid Receptor Modulators; D002219:Carbamates; D065127:Dopamine D2 Receptor Antagonists; D063388:Endocannabinoids; D009025:Morpholines; D009281:Naphthalenes; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D017448:Receptors, Dopamine D2; D016194:Receptors, N-Methyl-D-Aspartate; C500528:cyclohexyl carbamic acid 3'-carbamoylbiphenyl-3-yl ester; C103505:AM 251; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D012110:Reserpine; D016627:Oxidopamine; D004298:Dopamine