Tooth pulp evoked potentials in trigeminal nuclei and parabrachial region of the freely moving rat.

Twelve hooded rats with chronically implanted recording electrodes in the left ponto-mesencephalic trigeminal nuclei and parabrachial region and bipolar stimulating electrodes in the left upper incisor were investigated in different states of spontaneous behaviour. At all recording sites tooth pulp evoked potentials (TPEP) with the following main components were recorded: a small negative component with a peak time of N 2 ms, followed by a second negativity with the peak time of N 6 ms and a slow large positive-negative component with the peak time of N 28 ms. The corresponding positive peaks were: P 3 ms, P 13 ms, P 58 ms. In all rats we observed a great variability of TPEP components in different waking states. A maximal decrease of TPEPs was observed during strong grooming compared with relaxed wakefulness.