CESIUM PREVENTS MAINTENANCE OF LONG-TERM DEPRESSION IN RAT HIPPOCAMPAL CA1 NEURONS

LONG-TERM depression of field excitatory postsynaptic potentials (EPSP ) in the CA1 region of hippocampal slices was evoked by delivering a 1 5 min train of pulses at 1 Hz to the Schaffer-commissural-CA1 pathway, and prevented by adding an N-methyl-D-aspartate (NMDA) receptor antag onist (AP-5, 50 mu M) to the perfusing medium. Superfusion of the slic es with Cs (2 mM) during the 1 Hz stimulation period could both inhibi t the maintenance phase of the depression itself and elicit spontaneou s rhythmic activity. Cs had no effect on the postsynaptic response to the GABA-B agonist, baclofen. As a major effect of Cs is a block of th e hyperpolarization-activated current (I-h), these results suggest the possible involvement of I-h in the maintenance of long-term depressio n.