Adenosine depresses induction of LTP at the mossy fiber-CA3 synapse in vitro.

Using the hippocampal slice preparation, extracellular recordings of CA3 field excitatory postsynaptic potentials (fEPSPs) were performed to assess the effects of adenosine on the induction of mossy fiber long-term potentiation (LTP). When present during tetanization, adenosine (50 microM) significantly suppressed mossy fiber LTP whereas it failed to inhibit LTP when applied immediately after high-frequency stimulation. Based on the hypothesis that mossy fiber LTP is presynaptic in origin, our data thus provide first evidence that adenosine's presynaptic action alone is sufficiently powerful to interfere with synaptic plasticity.