Vagus nerve stimulation modifies the electrical activity of the olfactory bulb

Evoked potential and unit activity recording techniques were used to study the effects of the vagus nerve stimulation on the olfactory bulb. A biphasic potential was evoked in the olfactory bulb by a single pulse delivered to the vagus nerve. Half of the neurons studied decreased discharge frequency after single pulse or train stimulation. The interval during which neurons ceased activity corresponded to the duration of the negative wave of the evoked potential. Responsive neurons were marked with horseradish peroxidase applied iontophoretically. Responsive neurons were located in the periglomerular layer of the olfactory bulb. These results suggest the existence of a vagus nerve-olfactory bulb pathway. The functional significance of this pathway is discussed.