Stimulation to the Trigeminal Afferent Nerve of the Nose by Formaldehyde, Acrolein, and Acetaldehyde Gases

Abstract

This study was performed to elucidate the effect of formaldehyde (HCHO), acrolein (CH₂CHCHO), and acetaldehyde (CH₃CHO) gases on the nasal sensory system in the rat. For this purpose, the afferent activity was recorded from the ethmoidal nerve, one branch of the trigeminal nerve, during delivery of these gases (0.32–4.7 ppm HCHO, 0.78–7.2 ppm CH₂CHCHO, 134–2232 ppm CH₃CHO) into the upper airway at a flow rate of 200 ml/min. All compounds stimulated nerve activity when they and control gas were alternately applied into the nose. The concentration-response relationships, which were represented by log-log coordinates, showed that a 50% increase in nerve activity was found at 1.8, 1.2, and 908 ppm for HCHO, CH₂CHCHO, and CH₃CHO, respectively.

These results indicated that formaldehyde and acrolein can stimulate the nasal sensory system at concentrations less than I ppm, while such stimulation is much weaker with acetaldehyde. These stimulatory effects on the nasal passage will be associated with some respiratory reflexes such as a decrease in respiratory frequency and sensation of mucosal irritation.