Adenosine depression of hippocampal neurons in vitro: an intracellular study of dose-dependent actions on synaptic and membrane potentials.

In CA1 pyramidal neurons, 5 micrometer adenosine had no measurable effect on resting membrane potential or resistance, while excitatory and inhibitory postsynaptic potentials generated by orthodromic stimulation of the stratum radiatum were reduced by 20--60%. However, 10--20 micrometers adenosine not only markedly reduced (by 20--80%) the synaptic potentials, but also clearly hyperpolarized most pyramidal neurons. This effect was accompanied by a reduction in input resistance in about one-half of the cells and no measurable change in resistance in the rest. Monobutyryl cyclic AMP in concentrations of 50 micrometer or more also hyperpolarized neurons, usually no change in input resistance.