Fig. 2.

Action potentials evoked by the orthodromic stimulation of Schaffer collaterals in the hippocampal CA1 region. a Schematic diagram of the locations of recording electrode and orthodromic stimulation electrode. b Population spike (PS) evoked by a single pulse with a greater intensity 0.1 mA. c Unit spikes evoked by a single pulse with a smaller intensity 20 μA. Expanded waveforms below are examples of unit spikes from a pyramidal cell (Pyr) and an interneuron (Int), respectively. The baseline firing of the Pyr was a burst with three consecutive spikes. d Field EPSP (fEPSP) recorded in the stratum radiatum of CA1 region 200 μm from the pyramidal layer. Arrows denote stimulation artifacts with the red arrow indicating the first pulse of each stimulation train. The slope of fEPSP evoked by the first pulse was used to evaluate the strength of synaptic transmission