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The Journal of Neuroscience, 1999, 19:RC27:1-7

RAPID COMMUNICATION
Neocortical Synchronized Oscillations Induced by Thalamic Disinhibition In Vivo

Manuel A. Castro-Alamancos

Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A2B4 Canada

Thalamocortical circuits are recognized as the main elements involved in the genesis of synchronized oscillations typical of certain generalized seizures. We addressed the capability of thalamic disinhibition to generate synchronized oscillations in neocortex. Microdialysis was used to infuse GABA_A and GABA_B receptor antagonists directly into the thalamus of anesthetized rats while recording cortical field potentials from 16 sites aligned perpendicular to the cortical surface, using 100 µm spaced linear array silicon probes. The results demonstrate that block of thalamic GABA_A receptors induces continuous 3 Hz discharges in neocortex and that thalamic GABA_B receptors mediate this activity. Also, during thalamic disinhibition sporadic long-lasting discharges at 12 Hz occur that do not depend on GABA_B receptors. Current source density analysis of these activities revealed that the dynamics of sinks and sources for the 3 and 12 Hz discharges was quite distinct, in a way that suggests a different active involvement of the neocortex. The results indicate that intrathalamic inhibitory processes play an essential role in the generation of neocortical synchronized oscillatory activity that may be related to certain forms of generalized seizures.

Key words: epilepsy; seizure; oscillations; thalamus; neocortex; GABA

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Copyright © 0000 Society for Neuroscience  0270-6474/0/$05.00/0

This article has been cited by other articles:

				A. DESTEXHE and T. J. SEJNOWSKI Interactions Between Membrane Conductances Underlying Thalamocortical Slow-Wave Oscillations Physiol Rev, October 1, 2003; 83(4): 1401 - 1453. [Abstract] [Full Text] [PDF]

				M. A Castro-Alamancos and P. Rigas Synchronized oscillations caused by disinhibition in rodent neocortex are generated by recurrent synaptic activity mediated by AMPA receptors J. Physiol., July 15, 2002; 542(2): 567 - 581. [Abstract] [Full Text] [PDF]

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