Long-term potentiation and paired-pulse facilitation in the hippocampal CA1 region

Abstract

We have investigated the interaction between long-term potentiation (LTP) and paired-pulse facilitation (PPF) in the hippocampal CA1 region under different conditions of initial PPF. PPF is a short lasting presynaptic alteration in synaptic efficacy, determined by the presynaptic release probability, where a high and low PPF indicate a low and high release probability, respectively. LTP was associated with no, or only little, change in PPF, independent of the initial value of PPF and of the time of measurement within the first hour of LTP. These results support the notion that the expression mechanism of LTP is not regulated by the initial release probability and that LTP is due to a single expression mechanism within its first hour.