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Neuron-Astrocyte Coupling and its possible role in Epilepsy

The prejudice that the relation between neuroglial fibers and neuronal cells is similar to the relation between connective tissue and muscle or gland cells, that is, a passive weft for merely filling and support (and in the best case, a gangue for taking

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Neuron-Astrocyte Coupling and its possible role in Epilepsy

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  1. The prejudice that the relation between neuroglial fibers and neuronal cells is similar to the relation between connective tissue and muscle or gland cells, that is, a passive weft for merely filling and support (and in the best case, a gangue for taking nutritive juices), constitutes the main obstacle that the researcher needs to remove to get a rational concept about the activity of the neuroglia. —S Ramon y Cajal – astrocytes are not electrically excitable but Ca2+ excitable- one astrocyte contacts 1000s of synapses Ramon y Cajal Nedergaard et al., TINS 26, 523 (2003) Neuron-Astrocyte Coupling and its possible role in Epilepsy P. Jung, Department of Physics and Astronomy, Ohio University

  2. Astrocytes are Ca2+- excitable Cultured rat hippocampal astrocytes A.H. Cornell-Bell at al. Science, 247, 373 (1990)

  3. Intercellular Ca2+ Waves(Cornell-Bell et al., M. Sanderson, A. Charles) Speed: ~20µm/s Range: a few hundred µm Time scale: seconds to minutes

  4. mGluR Neurons talk to Astrcoytes Astrocyte processes enwrap synapse Fellin ei al., Physiology 21, 208 (2006) Tripartite Synapse (Araque et al. Trends Neurosci 22 (1999))

  5. Whisker stimulation (mice) Field - potential recording (barrel cortex) Astrocyte Ca In-vivo: whisker stimulation Wang et al., Nat Neurosci 9 (2006) (Nedergaard lab) neurons (red arrow)

  6. Astrocytes talk back to Neurons through release of glutamate Micro-island: neuron on astrocytes(culture) Parpura & Haydon, PNAS, 97 (2000) In slice: Fellin et al. , Neuron 43 (2004)

  7. Synchronized SICs in small domains(Fellin et al., Neuron 43 (2004)) Glutamate released from astrocyte activates slow, synchronous NMDA-mediated inward currents in domains of neurons

  8. Astrocytes and Epileptic Seizures Tian et al.:An astrocytic basis of epilepsy (Nature Medicine, 11 (2005) Epileptic discharges through local paroxysmal depolarization shift (PDS) driving groups pf neurons into synchronous bursting activity. • - Ca2+ increased in Astrocyte • – PDS - like epileptiform responses in neighboring neurons • – PDS in nearby neurons in in-vitro epilepsy models with blocked synaptic transmission • – Anti-epileptics reduced Ca2+ signal in astrocyte

  9. Epilepsy and astrocytes – in astrocytes from epileptic foci mGluRs are overexpressed by a factor of about 20 (rat models and human) (Ulas et al., Glia 30, 352 (2000), Tang and Lee, J. Neurocytology, 30, 137 (2001), Aronica et al. Europ.J. Neurosci., 12, 2333 (2000), – Enhanced IP3 Hydrolysis and increased Ca2+ spikes during epileptic seizure (Ong et al. J. Neurochem. 72, 1574 (1999) – More spontaneous astrocytic calcium spikes in epileptic (Tashiro et al., J. Neurobiol. 50, 45 (2002)

  10. Neuron-astrocyte feedback model(S.Nadkarni and P.J., Phys. Biol. 1 (2004))

  11. Large abundance of mGluR Astrocytes from epileptic foci: mGluRs are increased by a factor of about 20. Ulas et al., Glia 30, 352 (2000), Tang and Lee, J. Neurocytology, 30, 137 (2001),Aronica et al., Europ.J. Neurosci., 12, 2333 (2000) mGluR

  12. Publications S. Nadkarni and P.J., Dressed Neuron:modeling neural-glialinteractions,Phys. Biol. 1, 35 (2004) S. Nadkarni and P.J., Synaptic inhibition and pathological hyperexcitability through enhanced neuron-astrocyte interaction J.Integr. Neurosci, 4, 1 (2005) S.Nadkarni and P.J., Modeling synaptic transmission of the tripartite synapse, Phys. Biol. 4, 1 (2007) S. Nadkarni, P.J. and H. Levine, Astrocytes optimize synaptictransmission of information, submitted

  13. The prejudice that the relation between neuroglial fibers and neuronal cells is similar to the relation between connective tissue and muscle or gland cells, that is, a passive weft for merely filling and support (and in the best case, a gangue for taking nutritive juices), constitutes the main obstacle that the researcher needs to remove to get a rational concept about the activity of the neuroglia. —S Ramon y Cajal Arrangements of astrocytes and neurons in rat cortex– astrocytes are not electrically excitable but Ca2+ excitable- one astrocyte contacts 1000s of synapses Nedergaard et al., TINS 26, 523 (2003) Ramon y Cajal Astrocytes and Neurons

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