Neuron-glia Crosstalk And Long-term Neural Plasticity

Glial cells in CNS are usually classified as astrocyte, oligodendrocyte, andmicroglia. In addition, NG2+ glial cells, previously known as oligodendrocyteprecursor cells (OPCs), are recently recognized as a distinct macroglial cellpopulation due to their unique properties and their extensive distribution in adultbrain. In the present study, we found that induction of LTP in hippocampalneurons critically depends on astrocyte-released D-serine, a co-agonist of NMDAreceptors. We further showed that, in hippocampal slices, neuronal signaling toboth astrocyte and NG2 glial cell exhibited LTP-like plasticity following tetanusstimulation of Schaffer collaterals (Sc). In NG2+ glial cells receiving directglutamatergic synaptic inputs from neurons, the persistent enhancement ofpostsynaptic currents required intracellular Ca2+ elevation which induced byactivation of Ca2+ permeable AMPA receptors in NG2+ cells, while the persistentincrease in Sc-evoked depolarization in astrocytes was due to an increasedextracellular K+ accumulation accompanying LTP of neuronal synapses. Ourresults extend the concept of synaptic plasticity and may have significantimplications in the basic mechanisms of LTP induction and expression. The twodifferent forms of plasticity in neuron-glia cross-talking may have differentialphysiological relevance.