title: Blockade of mGluR glutamate receptors in the subthalamic nucleus ameliorates motor asymmetry in an animal model of Parkinson's disease.
abstract: It has been suggested that Group I metabotropic glutamate receptor antagonists could have potential therapeutic value in the treatment of Parkinson's disease. There is evidence that when given systemically, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a metabotropic glutamate receptor type 5 (mGluR5) antagonist, produces anti-parkinsonian effects in animal models, but the site of action has not been directly established. In the present study, we examined whether the subthalamic nucleus (STN) and its output structures may mediate such an effect using a unilateral rat model of Parkinson's disease. A battery of simple behavioral tests, reliably sensitive to dopamine depletion, was applied consecutively: (i) prior to surgery; (ii) 3 weeks following a unilateral 6-hydroxydopamine lesion of the substantia nigra pars compacta; (iii) at 1 h, 24 h and 4 days following a microinjection of MPEP, via an indwelling cannula, into the STN, entopeduncular nucleus (EP) or substantia nigra zona reticulata. Unilaterally dopamine-depleted animals typically had severe motor and sensorimotor asymmetries 3 weeks following surgery. Microinjection of 25 nmol MPEP into the STN of these animals significantly attenuated these asymmetries relative to vehicle. Further microinjections of lower doses (5 and 10 nmol) revealed a dose-response effect. Microinjection of MPEP into either the EP or substantia nigra zona reticulata was without effect. These data suggest that MPEP may act at the level of the STN to reduce glutamatergic overactivity and thereby induce anti-parkinsonian effects.
authors.affiliation: Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, 760 Westwood Plaza, Los Angeles, CA 90024, USA.
authors.forename: Janice M
authors.initials: JM
authors.lastname: Phillips
authors.forename: Hoa A
authors.initials: HA
authors.lastname: Lam
authors.forename: Larry C
authors.initials: LC
authors.lastname: Ackerson
authors.forename: Nigel T
authors.initials: NT
authors.lastname: Maidment
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D007839:Functional Laterality; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D016627:Oxidopamine / Q000633:toxicity; D010300:Parkinson Disease / Q000150:complications / Q000188:drug therapy / Q000209:etiology; D010302:Parkinson Disease, Secondary / Q000188:drug therapy / Q000503:physiopathology*; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000502:physiology*; D020531:Subthalamic Nucleus / Q000187:drug effects* / Q000502:physiology; D013565:Sympatholytics / Q000633:toxicity; D013997:Time Factors
chemical_list: D018691:Excitatory Amino Acid Antagonists; C578935:GRM5 protein, human; C578937:Grm5 protein, rat; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D013565:Sympatholytics; C121465:6-methyl-2-(phenylethynyl)pyridine; D016627:Oxidopamine; D004298:Dopamine