METHODS: Guinea pigs were placed in a transparent plastic 2 L plethysmography chamber equipped with a bias flow regulator that withdrew air at a rate of 2.5 L/min (Buxco, USA). 2mL of a 0.1mM solution of capsaicin was delivered into the camber using an ultrasonic nebulizer with an output of 0.6 mL/min, delivering an aerosol with an estimated median particle diameter of 0.9 mm (Aerogen, Ireland). Animals were exposed for 10 min. Coughs were counted for the 10 min exposure period. The experiment was visually monitored by the investigator. The baseline frequency of coughing in response to capsaicin was recorded for all animals and 7 days later, animals were anesthetized with diethyl ether. A small animal laryngoscope (Penn Century Inc, USA) was used to place the tip of a microsprayer (Penn Century Inc, USA) syringe in the oral cavity. Vehicle or Ax-8 (5 or 10mg/ml) was administered at 75ul per animal. 10 min after injection, the guinea pigs were exposed to the capsaicin mist and the number of coughs recorded. The three groups each had N=10 per group.