The role of the trigeminal nerve in olfaction

The effect of reversible blocking of the trigeminal nerve on olfactory stimulation was studied in rabbits with chronically implanted electrodes. In one series of experiments, blocking the trigeminal nerves at the level of the ganglia increased olfactory bulb excitability, but no cortical desynchronization was evident on odor presentation. Respiration and heart rate remained relatively unchanged during odor presentation. In the trigeminally blocked animal, olfactory bulb-induced sinusoidal wave activity was significantly increased in frequency and amplitude when compared with this activity in the unblocked animal following odor presentation. The present evidence supports the concept of a central regulatory control over olfactory afferent inputs; the trigeminal nerve plays an important role in this system.