Dendritic spine changes associated with hippocampal long-term synaptic plasticity

Long-term enhancement of synaptic efficacy in the hippocampus is an importa nt model for studying the cellular mechanisms of neuronal plasticity, circu it reorganization, and even learning and memory(1). Although these long-las ting functional changes are easy to induce, it has been very difficult to d emonstrate that they are accompanied or even caused by morphological change s on the subcellular level Here we combined a local superfusion technique(2 ,3) with two-photon imaging(4), which allowed us to scrutinize specific reg ions of the postsynaptic dendrite where we knew that the synaptic changes h ad to occur. We show that after induction of long-lasting (but not short-la sting) functional enhancement of synapses in area CAI, new spines appear on the postsynaptic dendrite, whereas in control regions on the same dendrite or in slices where long-term potentiation was blocked, no significant spin e growth occurred.