Cortical tooth pulp evoked potentials in freely moving rat.

The paper deals with the method of chronic implantation of electrodes for tooth pulp stimulation (TPS) in the upper incisor of rats, which enables investigations of tooth pulp evoked potentials (TPEP) under conditions of unrestrained behavior during several weeks. The most favorable point for recording TPEPs in the somatosensory cortex was 1 mm anterior of the bregma and lateral 3 mm below the crest of the skull. Here, TPEPs had amplitudes between 1000 and 2000 mikroV. TPEPs with amplitudes lower than 400 mikroV were recorded in other neocortical areas. The amplitudes of the primary components with peak times of 6 ms for positive and 12 ms for negative peaks were dependent on the behavioral state. The position of and distance between stimulation electrodes influence the TPEP. With increasing stimulus intensity TPEP amplitudes rised in an s-shaped curve. Current spread to alveolar nerve tested in acute experiments and was too small to evoke sufficiently large EPs of other origin.