ROLE OF ADENOSINE IN HETEROSYNAPTIC, POSTTETANIC DEPRESSION IN AREA CA1 OF HIPPOCAMPUS

Conditioning stimulation of afferent fibers in hippocampal area CA1 pr oduced heterosynaptic, posttetanic depression (PTD) of responses evoke d by stimulation of an independent set of afferent fibers. PTD was pre sent within 5 s of conditioning stimulation, amounted to a 60-80% redu ction of excitatory postsynaptic potentials (EPSPs), and required a pe riod of 3-5 min for recovery. Antagonists of A1 adenosine receptors su bstantially reduced PTD. Adenosine released into, or formed in, the ex tracellular space during conditioning stimulation may diffuse within t he slice to depress evoked release of glutamate,