Further characteristics of hippocampal CA1 cells in vitro

The effects of intracellular current injection on synaptic potentials and spike initiation were studied in hippocampal CA1 pyramidal cells in the in vitro slice preparation. Measures of cell charging time constant, resistance, and rheobase level were similar to those reported by other investigators working with intact preparations. Studies of spike initiation induced by injection of depolarizing ramp currents gave little evidence for a threshold accomodation in CA1 cells. Small amplitude fast-rising spike potentials occurred spontaneously and in association with synaptic excitation of neurons. It is argued that these potentials reflect active spike generation in the dendrites.