Central nervous mechanisms of cough

Cough is an airway defensive reflex substantially consisting in a modified respiratory act. Transection experiments have shown that the fundamental structures responsible for this reflex are located within the medulla oblongata. Electrical stimulation applied to the medulla failed to provide convincing evidence of a cough centre distinct from the brainstem respiratory network. In fact, electrical stimuli affect not only neuronal somata, but also intramedullary cough-related pathways. Studies on the behaviour of medullary respiratory neurones have led to the conclusion that the same respiratory neurones involved in the generation of the eupnoeic pattern of breathing also participate in the production of the cough motor pattern. These findings support the existence of multifunctional neural networks in the mammal brainstem. BoÈtzinger complex expiratory neurones with augmenting discharge patterns have been suggested to convey an excitatory drive to the expiratory bulbospinal neurones of the caudal ventral respiratory group and, hence, to expiratory motoneurones. The excitatory drive to caudal medullary expiratory neurones is mediated by ionotropic glutamate receptors. Recent lines of evidence indicate that the BoÈtzinger complex and the caudal ventral respiratory group have a crucial role in determining both the inspiratory and the expiratory components of the cough motor pattern.