Fig. 9.

Impact of intrinsic plasticity on neuronal responses to synaptic excitation. These experiments were performed in the absence of blockers of synaptic transmission in the control ACSF.A, Recordings from a regular firing CA1 pyramidal cell from a sham-control animal. Firing behavior was determined using long depolarizing current injections through the recording microelectrode (a). Single-shock stimuli were applied to afferent fibers in stratum radiatum and adjusted to evoke threshold-straddling EPSPs (b; different trials with identical stimulation intensity are shown). B, A similar experiment in a bursting neuron (a) from an SE-experienced animal (n = 4 cells). All suprathreshold EPSPs elicited a burst discharge (b; three different trials with identical stimulation intensity; 1.4 V). Application of 100 μm Ni²⁺ blocked the intrinsic bursts induced by depolarizing current pulses (comparea, c). It also slightly reduced the amplitude of the EPSPs without affecting their duration (data not shown). To elicit threshold EPSPs in the presence of 100 μm Ni²⁺, stimulation intensity was increased to 1.5 V (d, top trace). Under these conditions, the EPSP-evoked firing responses were converted to single spikes (d; middle andbottom traces).