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Properties of chemosensor subtypes innervating the guinea pig airways. |
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| C-Fiber |
C-Fiber |
Aδ-Fiber |
|
|
|
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| Anatomical Characteristics: |
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| 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 Expression2 |
Yes |
Yes |
Yes |
| Functional Characteristics: |
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| Conduction Velocity (m/sec) |
<1 |
<1 |
~6 |
| Mechanical Threshold |
High |
High |
High |
| Sensitive to: |
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| Punctate Mechanical |
Yes3 |
Yes3 |
Yes3 |
| Capsaicin |
Yes |
Yes |
Yes |
| Hypertonic Saline |
Unknown |
Yes |
Yes |
| Bradykinin |
Yes |
Yes |
Yes |
| Acid |
Yes |
Yes |
Yes |
| Inflation (≤50 cmH2O) |
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 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. | |||
Mazzone Cough 2005 1:2 doi:10.1186/1745-9974-1-2 |
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