DEVELOPMENTAL-CHANGES IN LONG-TERM POTENTIATION IN CA1 OF RAT HIPPOCAMPAL SLICES

Long-term potentiation (LTP) was examined in the CA1 region of rat hip pocampal slices at postnatal day 9 (P9), P15, P30, P60, P90, P120, and P300. A single 100 Hz x 1 sec tetanus failed to induce LTP in P9 slic es, while similar degrees of LTP were observed at P15, P30, and P60. A t P30, changes in population spike (PS) amplitudes were accurately pre dicted by changes in dendritic excitatory postsynaptic potentials (EPS Ps). However, at P15, the predicted increase in PS calculated from cor responding changes in dendritic EPSPs was significantly less than the observed increase, suggesting that EPSP-PS dissociation (ES-dissociati on) plays a substantial role in LTP at P15. Additionally, the correspo nding changes in somatic EPSP height measured in the CA1 cell layer di d not predict the E-S dissociation at P15, suggesting that the E-S dis sociation arises largely from changes in the excitability of the soma. Using a single 100 Hz x 1 sec tetanus, LTP proved difficult to induce in slices from rats greater than or equal to P90, with slices showing initial enhancement that faded over 60 min of monitoring. (C) 1995 Wi ley-Liss, Inc.