Airway receptors in cough

Area of Science:

• Physiology
• Respiratory System
• Neuroscience

Background:

• Sulphur dioxide (SO2) inhalation is known to affect respiratory reflexes.
• Airway receptors, including slowly adapting stretch receptors (SAR) and rapidly adapting irritant receptors (RAR), play crucial roles in respiratory control and reflexes like apnea and cough.

Purpose of the Study:

• To investigate the role of specific airway receptors in the cough reflex following SO2 inhalation.
• To compare the effects of SO2 on respiratory reflexes in rabbits and dogs.

Main Methods:

• Rabbits and dogs were anesthetized and mechanically ventilated.
• SO2 inhalation (200 ppm for rabbits, up to 1000 ppm for dogs) was administered.
• Cough responses to mechanical irritation of the trachea, carina, and larynx were assessed before and after SO2 exposure.
• Electrical activity of tracheal RAR was recorded in rabbits.

Main Results:

• In rabbits, SO2 (200 ppm) abolished the inflation apnea reflex and suppressed cough elicited by tracheobronchial stimulation, while laryngeal stimulation still induced a weaker cough.
• SO2 did not abolish inflation apnea or cough in dogs, even at higher concentrations.
• Tracheal RAR activity remained present in rabbits after SO2 exposure had eliminated cough and apnea.

Conclusions:

• Slowly adapting stretch receptors (SAR) appear to play a significant role in mediating the cough reflex, particularly in response to tracheobronchial stimulation.
• The differential effects of SO2 in rabbits and dogs highlight species-specific differences in respiratory reflex control mechanisms.