Fig. 3.

Development of a spike-evoked plateau potential triggered by NMDA treatment is blocked in CA1 pyramidal cells from cPLA₂α^−/− mice. (A) A sample trace illustrates the stimulation and recording protocol. Current-clamp recordings were combined with dendritic Ca²⁺ imaging; the latter data are shown in Fig. 4. Initially, a brief injection of hyperpolarizing current was delivered to allow for the measurement of R_input; 500 msec later, a 50-msec-long injection of depolarizing current was given. This current was calibrated at the outset of the experiment to reliably evoke a single spike and was held constant thereafter. Current-clamp recording continued until t = 0.8 sec to capture the evoked spike, and image acquisition continued until t = 1.2 sec to capture the spike-evoked Ca²⁺ transient. (B) Representative single traces of evoked spikes taken at the points indicated on the time-course graph in C. Time a (dark blue line) is at the start of the recording period. Time b (green line) occurs 12 min from the start of the experiment, which is after 4 min of NMDA exposure. Time c (light blue line) is 36 min after the start of recording and is the last time point in the experiment. The +/+ group was a control, in which cells from WT mice were recorded without NMDA challenge. (Scale bars: 10 msec.) (C) Time-course graphs showing population measures of electrophysiologic parameters. +/+ NMDA, n = 10; +/+, n = 5; −/− NMDA, n = 9. AP, action potential.