Averaged pre- and post-spike activity of a temperature insensitive VMPO neuron (A) and warm sensitive VMPO neuron (B). For each, averages of 10 action potentials (truncated) during baseline conditions and during perfusion with PGE2 (1 μM), are superimposed on the spike threshold (post-pike activity during PGE2 is indicated by an asterisk). These averages do not include pre-spike activity that contained putative postsynaptic potentials. For the temperature insensitive neuron in A, the rate of rise of the depolarizing prepotential increased from 0.17 mV·mSec-1 to 0.27 mV·mSec-1. For the warm sensitive neurons in B, the rate of rise of the depolarizing prepotential decreased from 0.38 mV·mSec-1 to 0.18 mV·mSec-1.