HIPPOCAMPAL LONG-TERM DEPRESSION - ARACHIDONIC-ACID AS A POTENTIAL RETROGRADE MESSENGER

Long-term depression (LTD) was studied in hippocampal slices from neon atal rats at the synapse between CA3 and CA1 pyramidal neurons. The in duction of LTD requires the pairing of Ca2+ influx into the postsynapt ic CA1 neuron through voltage-gated calcium channels with activation o f metabotropic glutamate receptors. The expression of this LTD is at l east partly presynaptic, implying the need for a retrograde messenger. We present evidence that arachidonic acid might serve such a function . Thus, arachidonic acid applications simulate LTD whereas blockade of arachidonic acid release inhibits LTD.