Adenosine‐mediated synaptic inhibition: Partial blockade by barium does not prevent anti‐epileptiform activity

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Abstract
Adenosine‐induced inhibition of evoked postsynaptic potentials (PSPs) and epileptiform burst firing in the CA1 subfield of rat hippocampal slices was studied with intracellular recordings in vitro. Adenosine (50 μM) caused a membrane hyperpolarization which was abolished during superfusion with 2 mM Ba2+. The adenosine‐induced inhibition of the PSPs was still evident, although the magnitude of the effect was significanty reduced. Adenosine also reduced Ba2+‐induced burst firing, but less effectively than it did bursts evoked by TEA (5 mM). The results suggest that adenosine inhibits synaptic transmission and epileptiform activity by at least 2 mechanisms: a postsynaptic barium‐sensitive increase in gK and a presynaptic effect independent of this adenosine‐evoked outward potassium conductance. © Wiley‐Liss, Inc.