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The Journal of Neuroscience, January 3, 2007, 27(1):251-259; doi:10.1523/JNEUROSCI.3815-06.2007

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 Previous Article

Development/Plasticity/Repair
ß/ Oscillatory Activity in the CA3 Hippocampal Area is Depressed by Aberrant GABAergic Transmission from the Dentate Gyrus after Seizures

Mario Treviño, Carmen Vivar, and Rafael Gutiérrez

Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados, México DF 07000, México

Correspondence should be addressed to Dr. Rafael Gutiérrez, Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados, Apartado Postal 14-740, México DF 07000, México. Email: grafael{at}fisio.cinvestav.mx

Oscillatory activity in the CA3 region is thought to be involved in the encoding and retrieval of information. These oscillations originate from the recurrent excitation between pyramidal cells that are entrained by the synchronous rhythmic inhibition of local interneurons. We show here that, after seizures, the dentate gyrus (DG) tonically inhibits ß/ (20–24 Hz) field oscillations in the CA3 area through GABA-mediated signaling. These oscillations originate in the interneuron network because they are maintained in the presence of ionotropic glutamate receptor antagonists, and they can be blocked by GABA_A receptor antagonists or by perfusion of a calcium-free extracellular medium. Inhibition of this oscillatory activity requires intact DG-to-CA3 connections, and it is suppressed by the activation of metabotropic glutamate receptors (mGluR). The influence of mGluR activation was reflected in the spontaneous subthreshold membrane oscillations of CA3 interneurons after one seizure but could also be observed in pyramidal cells after several seizures. Coincident stimulation of the DG at and ß/ frequencies produced a frequency-dependent excitation of interneurons and the inhibition of pyramidal cells. Indeed, these effects were maximal at the frequency that matched the mGluR-sensitive spontaneous field oscillations, suggesting a resonance phenomenon. Our results shed light on the mechanisms that may underlie the deficits in memory and cognition observed after epileptic seizures.

Key words: mossy fibers; plasticity; GABA; CA3; mGluR; oscillations

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Received Sept. 1, 2006; revised Nov. 29, 2006; accepted Dec. 1, 2006.

Correspondence should be addressed to Dr. Rafael Gutiérrez, Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados, Apartado Postal 14-740, México DF 07000, México. Email: grafael{at}fisio.cinvestav.mx

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				M. Uchigashima, M. Fukaya, M. Watanabe, and H. Kamiya Evidence against GABA Release from Glutamatergic Mossy Fiber Terminals in the Developing Hippocampus J. Neurosci., July 25, 2007; 27(30): 8088 - 8100. [Abstract] [Full Text] [PDF]

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