Conditioned enhancement of cough response in awake guinea pigs.

To determine whether psychological factors affect the cough response, we employed a classical conditioning procedure in which capsaicin challenge was paired with the presentation of an odor in awake guinea pigs. On days 1-4, animals received combined administrations of the unconditioning stimulus, capsaicin aerosols, and the conditioning stimulus, camphor aerosols (group 1), capsaicin and saline aerosols (group 2), and camphor and saline aerosols (group 3), and the number of coughs was counted. On day 5, all groups received camphor and saline aerosols. A significant number of coughs (p < 0.01) was observed only in group 1 when the animals were exposed to the odor alone on day 5. This suggests that associative learning enhances the cough response.