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. Negative correlation of the EP amplitude and instant respiration rate was found during relaxed wakefulness: it was less pronounced during periods with motor activities. At the same time direct parallelism between changes in EP and respiration rate was absent: the EP depression was maximal during grooming, while the respiration rate was minimal during exploratory behaviour.