As stated by Korpáš and Tomori (1979), cough is the most
important airway protective reflex which provides airway
defensive responses to nociceptive stimuli. They recognized that
active expiratory efforts, due to the activation of caudal ventral
respiratory group (cVRG) expiratory premotoneurons, are the
prominent component of coughs. Here, we discuss data
suggesting that neurons located in the cVRG have an essential
role in the generation of both the inspiratory and expiratory
components of the cough reflex. Some lines of evidence indicate
that cVRG expiratory neurons, when strongly activated, may
subserve the alternation of inspiratory and expiratory cough
bursts, possibly owing to the presence of axon collaterals. Of
note, experimental findings such as blockade or impairment of
glutamatergic transmission to the cVRG neurons lead to the view
that neurons located in the cVRG are crucial for the production of
the complete cough motor pattern. The involvement of
bulbospinal expiratory neurons seems unlikely since their
activation affects differentially expiratory and inspiratory muscles,
while their blockade does not affect baseline inspiratory activity.
Thus, other types of cVRG neurons with their medullary
projections should have a role and possibly contribute to the fine
tuning of the intensity of inspiratory and expiratory efforts.