I have a problem that the slope(mv/ms) of the excitatory post-synaptic
potential (EPSP) is unstable while recording baseline for LTP experiments. I
record for about 10 mins of baseline EPSP and I see the slope will rise
during this time. I use a concentric bipolar electrode and use 0.15ms pulse
width for stimulation. The slope I measure is in the initial 2 ms interval
of the EPSP. Since I am doing LTP experiments I have to give the
potentiating pulses within 15-17 mins after the whole-cell mode, but because
of the unstable slope I have to discard most of the cells. Also I use 100
micromoles of Picrotoxin in the bath.
Will greatly appreciate any help.