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The aim of this review is to provide an overview of current …

Biology Articles » Neurobiology » An overview of the sensory receptors regulating cough » Tables

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- An overview of the sensory receptors regulating 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.
Table 2
Properties of chemosensor subtypes innervating the guinea pig airways.

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 Expression2
 Yes
 Yes
 Yes




Functional Characteristics:


Conduction Velocity (m/sec)
 ~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 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.

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