An overview of the sensory receptors regulating cough

Cough

Table 1 Properties of low threshold mechanosensor subtypes innervating the guinea pig airways.

	SAR	RAR	Cough Receptor
Anatomical Characteristics:
Ganglionic Origin	Nodose	Nodose	Nodose
Extrapulmonary Termination	No	No	Yes
Intrapulmonary Termination	Yes	Yes	Few
Substance P Expression	No	No	No
TRPV1 Expression	No	No	No
*Functional Characteristics:*
Conduction Velocity (m/sec)	~18 (Aβ)	~15 (Aβ)	~5 (Aδ)
Mechanical Threshold	Low	Low	Low
Sensitive to:
Punctate Mechanical	Yes	Yes	Yes
Capsaicin	Yes¹	Yes¹	No
Hypertonic Saline	Unknown	Unknown	Yes
Bradykinin	Yes¹	Yes¹	No
Acid	No	Unknown	Yes
Inflation (≤50 cmH₂O)	Yes	Yes	No
Deflation/Collapse	No	Yes	No
Stretch	Yes	Yes	No
Bronchoconstriction	Yes	Yes	No
ATP	Yes	Yes	No
Reflex Effects on Respiration	Hering-Breuer	Tachypnea	Cough

¹ SARs and RARs are insensitive to the direct action of these chemicals on the nerve terminal. However, chemical stimuli such as capsaicin and bradykinin can activate SARs and RARs secondary to airway smooth muscle contraction, mucous secretion or edema formation. Cough receptors are insensitive to both the direct and indirect actions of capsaicin and bradykinin. See text for references.