Long-term potentiation: A developmental study in the freely-moving rat

Hippocampal dentate granule cell field potentials were recorded from 30- and 90-day old rats before, and at timepoints out to 24 hrs after tetanization of the perforant pathway. Evoked field potentials were analyzed for tetanization-induced changes in measures of the population EPSP slope (a measure of synaptic drive) and the population spike amplitude (a measure of cellular discharge). The results indicate a dissociation between potentiation of the EPSP slope and population spike components of the granule cell response in 30-day old animals. This is reflected as a greater net rise in transmission efficacy than that obtained in the 90-day age group. The results of early efforts to characterize the dentate granule response in freely-moving 15-day old animals are also presented.