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.

Mazzone Cough 2005 1:2   doi:10.1186/1745-9974-1-2