To assess the role of nasal/tracheal (N/T) breathing in the respiratory patterning of the olfactory bulb (OB) neurons, the activity of 21 units was recorded in 6 anesthetized rats set with a cannula enabling reversible tracheotomy: the rats could inhalate either through nasal pathways or through trachea directly. Shift from tracheal to nasal breathing induced respiratory patterning in 7 units. The changes were steady, reversible and reproducible. The present data, matched with previous ones, indicate that tracheotomy and anesthesia decrease the occurrence of respiratory patterning in OB neurons. The experiments also suggest that peripheral as well as central structures may be a source of respiratory modulation in the olfactory bulb.