Changes in[Ca2+]i during adenosine triphosphate-induced synaptic plasticity in hippocampal CA1 neurons of the guinea pig

The perfusion of adenosine triphosphate (ATP) induces long-term potentiation (LTP) in CA1 synapses of hippocampal slices, whereas the perfusion of ATP plus D,L-2-amino-5-phosphonovaleric acid (AP5) can result in the formation of long-term depression (LTD). To clarify the difference in change of intracellular calcium concentration ([Ca2+](i)) corresponding to induction of LTP or LTD, we measured [Ca2+](i) during the perfusion of ATP or ATP + AP5, while simultaneously recording evoked field potentials. In both cases, ATP (or ATP + AP5) perfusion transiently increased [Ca2+](i) but the extent of increase of [Ca2+](i) by ATP was larger than that caused by ATP + AP5. Thus, the larger rise in [Ca2+](i) induces LTP but the smaller rise induces LTD. These results are consistent with the Ca2+ hypothesis as proposed by Lisman (Trends Neurosci. 17 (1994) 406). (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.