Tooth pulp evoked potential in the thalamus of freely moving rats.

Eleven hooded rats with bipolar stimulating electrodes in the left upper incisor and recording electrodes in the ventral posteromedial (VPM), ventral dorsomedial (VDM) and paracentral (NPC) nuclei of the contralateral thalamus and the somatosensory cortex (SC) were investigated in different states of spontaneous behaviour. The early complex of the thalamic averaged tooth pulp evoked potentials (TPEP) consisted of two negative-positive waves, a small (N2, P4) and a larger one (N6, P14). Later components appeared with different peak times and amplitudes depending on the localization of the recording electrode. The single components of the thalamic TPEP decreased differently during behavioural activation between 20 and 80% with maximal expression during intensive grooming.