Peripheral opioid receptors and the cough reflex.

The cough reflex originates from stimulation of sensory nerve endings located in the upper and lower respiratory tract. Opiates are among the most potent and widely used drugs which inhibit the cough reflex, and it has been generally assumed that they act generally. However, opioid receptors have been identified on the sensory arm of the vagus nerve. Although the functional significance of these receptors is not clear, recent evidence suggests that their activation may be involved in the modulation of airway reflexes. This review briefly examines the evidence to support the hypothesis that opioid receptors on vagal sensory nerves may mediate peripheral opioid-induced antitussive activity.