Time-course of changes in firing rates and firing patterns of subthalamic nucleus neuronal activity after 6-OHDA-induced dopamine depletion in rats.
The subthalamic nucleus (STN) plays a key role in motor control. Disorganization of its neuronal activity is implicated in the manifestation of parkinsonian motor symptoms. The aim of the present work was to study the time-course of changes in the firing activity of STN neurons in a rat model of parkinsonism. Electrophysiological recordings were done in normal rats and four groups of rats at different time points after 6-hydroxydopamine (6-OHDA) microinjection into the pars compacta of substantia nigra (SNc). Results showed a significant decrease in firing rate during the first and second weeks post lesion (5.53+/-0.56 and 7.66+/-0.73 spikes/s, respectively) compared to normal rats (11.13+/-0.59 spikes/s). From the 3rd week after 6-OHDA injection the firing rates returned toward baseline, with an average of 9.71+/-0.51 spikes/s during the 3rd week and 11.13+/-0.71 spikes/s during the 4th week. With regard to firing pattern, the majority of STN cells (90%) discharged regularly or slightly irregularly in normal animals. Only 4% exhibited burst activity and 6% had mixed firing patterns. After SNc-lesion, the percentage of cells exhibiting burst and mixed patterns increased progressively from 35% during the first week to 56% at week 4 post-lesion. In sum, these experiments revealed that the firing rate of STN neurons was altered only transiently following nigral lesions, whereas a progressive and stable change in the firing pattern was observed up to 4 weeks post lesion, suggesting that the persistence of bursts firing more closely relates to the motor pathologies of this rat model of parkinsonism.
Ni
Z G
ZG
Laboratoire de Neuroscience Préclinique, INSERM U. 318, CHU - Pavillon B, B.P. 217, 38043 Cedex 09, Grenoble, France.
Bouali-Benazzouz
R
R
Gao
D M
DM
Benabid
A L
AL
Benazzouz
A
A
D000200:Action Potentials / Q000502:physiology*; D018663:Adrenergic Agents / Q000633:toxicity; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D016627:Oxidopamine / Q000633:toxicity*; D020734:Parkinsonian Disorders / Q000139:chemically induced* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020531:Subthalamic Nucleus / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D018663:Adrenergic Agents; D016627:Oxidopamine; D004298:Dopamine