Abstract
The synaptic plasticity process of long-term potentiation (LTP) and long-term depression (LTD) is vital for memory formation and overall neural health. However, mechanisms must be in place to prevent pathologically excessive LTP and LTD. Such regulation comes partly through metaplasticity, whereby neural activity at one point in time influences later plasticity. We have discovered a unique trans-regional mode of metaplasticity in the hippocampus, whereby "priming" stimulation of inputs to the basilar dendrites of pyramidal cells in area CA1, inhibits later LTP at synapses in the middle molecular layer (MML) of the dentate gyrus, a neighbouring region ~800 microns away. As there are no known neuronal connections between these brain regions, we tested the hypothesis that the metaplasticity is in fact accomplished via astrocytic networks.