Representation of capsaicin-evoked urge-to-cough in the human brain using functional magnetic resonance imaging.
BACKGROUND
Coughing in humans is typically preceded by a desire (or urge) to cough. The neural circuitry involved in sensing airway irritation and generating the urge-to-cough in humans is essentially unknown.


OBJECTIVE
The aim of the present study was to use functional brain imaging to describe the supramedullary regions that are activated in humans during capsaicin inhalation.


METHODS
Experiments were performed on 10 healthy subjects (5 males, 5 females). Capsaicin doses were individually tailored to evoke a transient and reversible urge-to-cough. Blood oxygen level-dependent (BOLD) functional magnetic resonance measures were collected during repeated 24-second challenges with capsaicin or saline inhalation and subjects were asked to rate the urge-to-cough intensity of each challenge.


RESULTS
Capsaicin inhalation reliably evoked an urge-to-cough, which was associated with activations in a variety of brain regions, including the insula cortex, anterior midcingulate cortex, primary sensory cortex, orbitofrontal cortex, supplementary motor area, and cerebellum.


CONCLUSIONS
These data provide the first insights into the cortical neuronal network involved in sensing airway irritation and modulating coughing in humans.
Mazzone
Stuart B
SB
The Howard Florey Institute, University of Melbourne, Parkville, Victoria, Australia 3010. smazzone@florey.edu.au
McLennan
Lisa
L
McGovern
Alice E
AE
Egan
Gary F
GF
Farrell
Michael J
MJ
D000280:Administration, Inhalation; D000328:Adult; D001921:Brain / Q000502:physiology*; D002211:Capsaicin / Q000008:administration & dosage*; D003371:Cough / Q000139:chemically induced*; D005260:Female; D006801:Humans; D007509:Irritants / Q000008:administration & dosage*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009299:Nasal Provocation Tests; D012018:Reflex / Q000502:physiology
D007509:Irritants; D002211:Capsaicin