title: Chronic L-DOPA administration increases the firing rate but does not reverse enhanced slow frequency oscillatory activity and synchronization in substantia nigra pars reticulata neurons from 6-hydroxydopamine-lesioned rats.
abstract: The pathophysiology of Parkinson's disease (PD) and of L-DOPA-induced dyskinesia (LID) is associated with dysfunctional neuronal activity in several nuclei of the basal ganglia. Moreover, high levels of oscillatory activity and synchronization have also been described in both intra- and inter-basal ganglia nuclei and the cerebral cortex. However, the relevance of these alterations in the motor symptomatology related to Parkinsonism and LID is not fully understood. Recently, we have shown that subthalamic neuronal activity correlates with axial abnormal movements and that a subthalamic nucleus (STN) lesion partially reduces LID severity as well as the expression of some striatal molecular modifications. The aim of the present study was to assess, through single-unit extracellular recording techniques under urethane anaesthesia, neuronal activity of the substantia nigra pars reticulata (SNr) and its relationship with LID and STN hyperactivity together with oscillatory and synchronization between these nuclei and the cerebral cortex in 6-OHDA-lesioned and dyskinetic rats. Twenty-four hours after the last injection of L-DOPA the firing rate and the inhibitory response to an acute challenge of L-DOPA of SNr neurons from dyskinetic animals were increased with respect to those found in intact and 6-OHDA-lesioned rats. Moreover, there was a significant correlation between the mean firing rate of SNr neurons and the severity of the abnormal movements (limb and orolingual subtypes). There was also a significant correlation between the firing activity of SNr and STN neurons recorded from dyskinetic rats. In addition, low frequency band oscillatory activity and synchronization both within the SNr or STN and with the cerebral cortex were enhanced in 6-OHDA-lesioned animals and not or slightly affected by chronic treatment with L-DOPA. Altogether, these results indicate that neuronal SNr firing activity is relevant in dyskinesia and may be driven by STN hyperactivity. Conversely, low frequency oscillatory activity and synchronization seem to be more important in PD because they are not influenced by prolonged L-DOPA administration.
authors: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, 48940 Leioa, Spain.
authors: A
authors: A
authors: Aristieta
authors: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, 48940 Leioa, Spain; Department of Pharmacology, Faculty of Pharmacy, University of the Basque Country, 01006 Vitoria-Gasteiz, Spain.
authors: J A
authors: JA
authors: Ruiz-Ortega
authors: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, 48940 Leioa, Spain; Department of Pharmacology, Faculty of Pharmacy, University of the Basque Country, 01006 Vitoria-Gasteiz, Spain.
authors: C
authors: C
authors: Miguelez
authors: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, 48940 Leioa, Spain.
authors: T
authors: T
authors: Morera-Herreras
authors: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, 48940 Leioa, Spain. Electronic address: luisa.ugedo@ehu.eus.
authors: L
authors: L
authors: Ugedo
mesh_terms: D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D058256:Brain Waves / Q000187:drug effects*; D002540:Cerebral Cortex / Q000187:drug effects / Q000503:physiopathology; D004195:Disease Models, Animal; D004409:Dyskinesia, Drug-Induced / Q000503:physiopathology*; D059330:GABAergic Neurons / Q000187:drug effects / Q000502:physiology; D007980:Levodopa / Q000008:administration & dosage*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D016627:Oxidopamine / Q000008:administration & dosage; D020734:Parkinsonian Disorders / Q000139:chemically induced / Q000503:physiopathology*; D065841:Pars Reticulata / Q000187:drug effects / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020531:Subthalamic Nucleus / Q000187:drug effects / Q000503:physiopathology
chemical_list: D007980:Levodopa; D016627:Oxidopamine
keywords: Dyskinesia; In vivo extra-unit recording; Oscillatory activity; Parkinson's disease; Synchronization