Interaction between paired-pulse facilitation and long-term potentiation in the projection from hippocampal area CA1 to the subiculum

STUDIES of the interaction between long-term potentiation (LTP) and paired- pulse facilitation (PPF) may throw light on the role of presynaptic factors in LTP. We examine here, for the first time, the nature of PPF in the CA1- subiculum projection. PPF peaks at a 50 ms interstimulus interval (ISI) and is evident at ISIs from 10 to 500 ms. There is no PPF effect at a 1000 ms ISI. PPF decreases in magnitude post-LTP induction across the middle range of ISI values tested (30, 50 and 100 ms). There is a positive correlation b etween initial PPF values and LTP; this correlation increases as the ISI in creases. Initial values and the change in PPF post-LTP are also negatively correlated. (C) 1998 Lippincott Williams & Wilkins.