Comparative sensitivity to adenosine of paired-pulse inhibition and single field potentials in the rat hippocampus

If excitatory terminals onto inhibitory interneurones were more sensitive to adenosine than excitatory terminals onto pyramidal cells in the hippocampus it might explain the effect of adenosine to decrease paired-pulse inhibition and account for reported excitatory effects of low concentrations of adenosine. We have compared the concentration-response relationships for the effect of adenosine on single evoked field potentials and on paired-pulse inhibition in the CA1 area of the rat hippocampal slice in order to test this hypothesis. Adenosine caused a concentration-dependent decrease in both single evoked population spike size and in paired-pulse inhibition between potentials. The concentration-response relationships for both effects was very similar, ruling out the possibility that excitatory terminals onto inhibitory interneurones are more sensitive to adenosine than excitatory terminals onto pyramidal cells, and suggesting that the receptors located at the two sites may be indistinguishable.