READILY RELEASABLE POOL SIZE CHANGES ASSOCIATED WITH LONG-TERM DEPRESSION

We have estimated, for hippocampal neurons in culture, the size of the autaptic readily releasable pool before and after stimulation of the sort that produces culture Long term depression (LTD). This stimulatio n protocol causes a decrease in the pool size that is proportional to the depression of synaptic currents. To determine if depression in thi s system is synapse specific rather than general, we have also monitor ed synaptic transmission between pairs of cultured hippocampal neurons that are autaptically and reciprocally interconnected. We find that t he change in synaptic strength is restricted to the synapses on the ta rget neuron that were active during LTD induction. When viewed from th e perspective of the presynaptic neuron, however, synapse specificity is partial rather than complete: synapses active during induction that were not on the target neuron were partially depressed.