Ozone-induced vagal reflex modulates airways reactivity in rabbits

We examined the effects of ozone (O3) on central and peripheral airway reactivity and tracheal transepithelial potential difference (PD) in New Zealand white rabbits. Rabbits were exposed for 7 h to either room temperature-humidified filtered air (n = 7) or 0.2 ppm O3 in humidified room air (n = 5). Tracheal PD was recorded 3 h after exposure. Whole lung resistance (RL) and reactivity were partitioned into their central (RC) and peripheral (RP) components using a retrograde catheter and forced oscillation. Changes in RL, RC, and RP in response to NaCl (0.9%) and ACh (100 mM) aerosol challenges were measured before and after vagotomy. Exposure to O3 decreased tracheal PD from -29 +/- 0.6 mV in air-exposed rabbits to -15 +/- 2 mV in O3-exposed rabbits (p < or = 0.0001). Exposure to O3 did not alter RL, RC, or RP. However, the ACh-induced increase in RL in O3-exposed rabbits (140%) was twice that recorded in the air-exposed group (p < or = 0.01). While changes in RP dominated the whole lung response to ACh in air-exposed rabbits, changes in RC were most prominent in the O3-exposed group. Bilateral vagotomy did not alter airway reactivity in control rabbits but did enhance peripheral lung reactivity in O3-exposed rabbits. We conclude that exposure to 0.2 ppm O3 for 7 h affects tracheal epithelial function in rabbits and increases central airway reactivity via vagal mechanisms without altering baseline RL, RC, or RP.