The good cough and the bad cough: treating coughs in a more targeted way
Researchers might be able to treat a troublesome cough in disease without disrupting the protective cough we need for optimal lung health, by targeting the different brain circuits involved.
More people seek medical advice for an unwanted, nagging cough than any other ailment. In some people their cough can persist for years without relief, as effective treatments are not readily available.
These findings from Australian researchers including Professor Stuart Mazzone from the Department of Anatomy and Neuroscience have very important implications for understanding and potentially treating cough disorders because it appears that different types of coughs may use different brain circuits.
Professor Stuart Mazzone heads the Mazzone Laboratory within the School of Biomedical Sciences, which is internationally recognised for remarkable work in the field of cough and respiratory sensation.
Previous research in animals and humans suggested that the brain processes all inputs from cough sensory nerves in a single area. However, in an earlier study using guinea pigs, published this year in The Journal of Physiology, the same research team from the University of Melbourne and Monash University demonstrated that this is unlikely to be true.
Instead, Prof. Stuart Mazzone and his team discovered that separate pathways in the brain are involved in the response to a good (needed to clear airways, to ensure optimal lung health) vs a bad cough (a sign of disease).
In this new study, human participants underwent behavioural testing to assess cough reflex sensitivity followed by functional brain imaging in an MRI scanner while inhaling different chemical substances.
The outcome showed that capsaicin inhalation activated both the nucleus of the solitary tract and the area of the brainstem containing the paratrigeminal nucleus, whereas ATP inhalation only activated the nucleus of the solitary tract.
Commenting on the study, senior author Professor Stuart Mazzone said:
“We have found two circuits in the brain for cough when previously it was believed only one existed. This creates opportunities to target one pathway without impacting the other and if our understanding of cough is correct then we maybe able to treat troublesome coughing in disease without affecting protective cough needed to clear the lungs (for example, when food ‘goes down the wrong way’) – this is the holy grail in the field. We are now assessing how the circuits function in patients with chronic cough and have plans to conduct trials to better control cough through modulating the activity in this newly discovered brain circuit. However, renewed funding is now critical to keep this work moving forward!”
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