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29. október 2009 Fyrirlestur Ragnhildar KáradótturTaugavísindafélagið vill vekja athygli á fyrirlestri Ragnhildar Þóru Káradóttur föstudaginn 30. október kl. 15:30. Fyrirlesturinn verður haldinn í húsakynnum Háskólans í Reykjavík, Kringlunni 1, stofu K-5. Útdráttur úr fyrirlestri Ragnhildar og aðrar upplýsingar má finna hér að neðan. 
Ragnhildur Þóra Káradóttir
Dorothy Hodgkin Research Fellow of the Royal Society
Department of Veterinary Medicine, University of Cambridge Abstract
Neuregulin expressed by axons can regulate myelination by signalling to ErbB receptors on myelinating cells. Furthermore, in CNS grey matter, neuregulin increases the expression of NMDA receptors. Oligodendrocytes at all developmental stages in the white matter exhibit NMDA evoked currents, mediated by receptors which show very weak magnesium block and are expressed in the myelin (Káradóttir et al., 2005, 2008), indicating that they might play a role in myelination.
We now use an assay in which cortical oligodendrocytes ensheath dorsal root ganglion cells (Wang et. al., 2006) to show that neuregulin and NMDA receptors interact to regulate myelination. Without neuregulin, blocking NMDA receptors had no effect on myelination. Adding neuregulin (in the form of the extracellular domain of NRG1-b1, 10ng/ml) increased myelination by 60%, and led to the majority of myelination being dependent on activation of NMDA receptors: NMDA receptor block decreased myelination by 80%. Blocking action potentials with TTX also had no effect in the absence of neuregulin, but greatly reduced myelination in the presence of neuregulin. Neuregulin's effect was associated with a 4-fold increase in NMDA receptor current in oligodendrocyte lineage cells. Thus, neuregulin apparently switches myelination from a default programme, that is independent of neuronal activity, to a mechanism that is regulated by glutamate released from active axons.
These data reveal a function for oligodendrocyte NMDA receptors, and could provide a novel white matter explanation for how the linkage of neuregulin to schizophrenia can be reconciled with schizophrenia involving a malfunction of NMDA receptors. The absence of
neuregulin in multiple sclerosis lesions, and restoration of myelination by added neuregulin, suggest a role for neuregulin/NMDA receptor dependent remyelination after pathology.
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