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Single-unit analysis of substantia nigra pars reticulata neurons in freely behaving rats with genetic absence epilepsy.
Deransart C, Hellwig B, Heupel-Reuter M, Leger JF, Heck D, Lucking CH.
Department
of Neurology, Neurozentrum, Institute of Biology III, Albert-Ludwigs
Universitat Freiburg, Freiburg, Germany. colin.deransart@ujfgrenoble.fr
PURPOSE:
The substantia nigra pars reticulata (SNpr) is assumed to be involved
in the control of several kinds of epileptic seizures, an assumption
based mostly on neuropharmacologic evidence. However, only very few
neurophysiological recordings from the basal ganglia support
neuropharmacologic data. We investigated the electrophysiologic
activity of SNpr neurons in rats with genetic absence epilepsy.
METHODS: Electrocorticography (ECoG) and multi-unit recordings using
permanently implanted tetrodes were obtained in freely behaving rats.
After spike sorting, auto- and cross-correlation analysis was used to
detect oscillatory neuronal activities and synchronizations. RESULTS:
During interictal periods, neither oscillation nor synchronization
could be observed in the firing patterns of SNpr neurons. At the
beginning of the absence seizure, the firing rate increased
significantly. The SNpr neurons started firing in bursts of action
potentials. Bursts were highly correlated to the spike-and-wave
discharges (SWDs) in the ECoG, mainly after the spike component of the
cortical spike-and-wave complex. Moreover, pairs of SNpr neurons tended
to fire synchronously. Before the end of the seizure, the firing rate
decreased progressively, and the burst-firing pattern ended at or
before the end of the SWDs. Once the SWDs had stopped, the SNpr neurons
resumed their basal firing pattern as before the seizure onset.
CONCLUSIONS: These results provide electrophysiologic evidence that
firing patterns and synchronization of SNpr neurons are in phase with
the occurrence of SWDs. The findings support the concept that nigral
control mechanisms are involved in modulating the propagation of an
ongoing generalized seizure.
PMID: 14636321 [PubMed - indexed for MEDLINE]
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