Effects of formaldehyde and ozone on the trigeminal nasal sensory system

The effects of formaldehyde and ozone on the electrical activity of the nasopalatine nerve were studied in anesthetized rats. The response (increase in action potential frequency) of nasopalatine and ethmoidal nerves to brief presentations of formaldehyde, ozone, or amyl alcohol was a power function of stimulus concentration. When formaldehyde was presented continuously for one hour, it produced a decrease in nasopalatine nerve response to amyl alcohol that varied directly with the formaldehyde concentrations employed. Perfusion of the nasal cavities with air for one hour following the formaldehyde exposure resulted in a partial recovery of the neural response to amyl alcohol. Ozone exposures of 5 ppm lasting one hour produced an increase in nasopalatine nerve response to amyl alcohol. Air perfusion following the ozone exposure reduced the neural response to amyl alcohol, but not to preexposure levels.