Field excitatory postsynaptic potentials (fEPSPs) were recorded from CA1b stratum radiatum using a single glass pipette (2-3 MΩ). Bipolar stainless steel stimulation electrodes (25 μm diameter, FHC) were positioned at two sites (CA1a and CA1c) in the apical Schaffer collateral-commissural projections to provide activation of separate converging pathways of CA1b pyramidal cells. Pulses were administered in an alternating fashion to the two electrodes at 0.03 Hz using a current that elicited a 50% maximal response. After establishing a stable baseline, long-term potentiation (LTP) was induced by delivering 5 or 10 ‘theta’ bursts (each burst was four pulses at 100 Hz and bursts were separated by 200 msec). Data were collected and digitized by NAC 2.0 Neurodata Acquisition System (Theta Burst Corp.).
