ENDOGENOUS ADENOSINE ATTENUATES LONG-TERM DEPRESSION AND DEPOTENTIATION IN THE CA1 REGION OF THE RAT HIPPOCAMPUS

This study tested the hypothesis that endogenous adenosine, a neuromod ulator which is known to modify long-term potentiation (LTP), might al so affect other forms of long-lasting synaptic plasticity, namely long -term depression (LTD) and depotentiation, in the hippocampus. Long-te rm depression was induced by applying low-frequency stimulation (LFS; 1 Hz, 900 stimuli, test intensity) to the Schaffer collateral-commissu ral fibres in hippocampal slices taken from young (12-14-day old) anim als. Depotentiation was induced by delivering LFS to a pathway in whic h LTP had previously been saturated. Under control conditions, LTD ind uced in two distinct pathways was similar. However, low-frequency stim ulation, applied in either pathway in the presence ed the selective ad enosine Al receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DP CPX; 10 nM), resulted in LTD which was larger than in control conditio ns. In a similar way, while under control conditions depotentiation in duced in two distinct pathways was similar, when LFS was applied in th e presence of DPCPX (10 nM) facilitation of depotentiation was observe d. These results suggest that endogenous adenosine, acting through ade nosine Al receptors, is able to attenuate long-term depression and dep otentiation in the hippocampus. (C) 1997 Elsevier Science Ltd.