Behaviour-dependent variability of potentials in the somatosensory cortex evoked by stimulation of the trigeminal nuclei in freely moving rats.

Nine hooded rats with chronically implanted epidural recording electrodes on the right primary somatosensory cortex, the olfactory bulb and bipolar stimulating electrodes in the left ponto-mesencephalic trigeminal nuclei and parabrachial region were investigated during different patterns of spontaneous behaviour. The early positive-negative component of the TNEP with peak times P5 and NII (ms) appeared about 1 ms earlier than after tooth pulp stimulation. The amplitude P5-N11 was slightly increased during drowsiness, decreased during slow wave sleep and was strongly decreased in behavioural patterns with movements, always compared with relaxed wakefulness.

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.

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.

[Variability of cortical evoked potentials in response to tooth pulp stimulation in the freely moving rat].

Evoked potentials (EP) due to the stimulation of the upper incisor tooth pulp were recorded from the somatosensory cortex of the freely moving adult rats. Background EEG, motor activity of an animal and respiratory potentials of the olfactory bulb were recorded simultaneously. EP configurations and mean amplitudes of primary complex (P1 + N1) differed significantly during states of sleep, drowsiness, relaxed wakefulness, grooming and exploratory behaviour; primary complex amplitude during intensive motor activities was several times less than during periods without movements.

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.