Fig. 3.

Nasal (−)-menthol vapor evoked respiratory slowing (A) and markedly inhibited citric acid–evoked coughing (B) in anesthetized guinea pigs, whereas nasal (+)-menthol challenges were without marked effects. The menthol vapors (carried by warm air) were delivered via a nasal cannula that was inserted into a nostril 2 min prior to (as indicated by the arrow) initiation of the challenges (which began at time 0). *Indicates a statistically significant decrease in respiratory rate and a statistically significant inhibition of citric acid–evoked coughing. Each data point represents the mean ± SE of 4–9 experiments.