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Table 2 Properties of chemosensor subtypes innervating the guinea pig airways.

From: An overview of the sensory receptors regulating cough

 

C-Fiber

C-Fiber

Aδ-Fiber

Anatomical Characteristics:

   

Ganglionic Origin

Nodose

Jugular

Jugular

Extrapulmonary Termination

No

Yes

Yes

Intrapulmonary Termination

Yes

Yes

Few

Substance P Expression (%) 1

Yes (50)

Yes (90–100)

No (0)

TRPV1 Expression 2

Yes

Yes

Yes

Functional Characteristics:

   

Conduction Velocity (m/sec)

<1

<1

~6

Mechanical Threshold

High

High

High

Sensitive to:

   

   Punctate Mechanical

Yes3

Yes3

Yes3

   Capsaicin

Yes

Yes

Yes

   Hypertonic Saline

Unknown

Yes

Yes

   Bradykinin

Yes

Yes

Yes

   Acid

Yes

Yes

Yes

   Inflation (≤50 cmH 2 O)

No

No

No

   Deflation/Collapse

No

No

No

   Stretch

No

No

No

   Bronchoconstriction

No

No

No

   ATP

Yes

No

No

   Serotonin (5-HT)

Yes

No

Unknown

Reflex Effects on Respiration

Apnea4

Apnea4

Apnea4

  1. 1 Percentage of soma expressing substance P shown in parentheses [taken from ref 36]. 2 Functionally responsive to capsaicin and/or TRPV1 detected immunohistochemically. There is no data available indicating percentage of cells expressing TRPV1. 3 All airway afferents are responsive to punctate mechanical stimulation. However, the threshold for activation is approximately 100 fold higher for chemosensors compared to mechanosensors. 4 The basic respiratory reflex evoked by capsaicin is apnea or respiratory slowing, often proceeded by rapid shallow breathing. However, the precise reflex response evoked by each chemosensor subtype has not been described. See text for references.