Fig. 1.

A schematic highlighting the potential effects of viral infection on vagus nerve activity. (I) Viral infection of epithelial cells can lead to release of mediators that stimulate action potential discharge in afferent nerves, thereby alerting the central nervous system. Viral infection can also lead to the production and release of neurotrophic factors that can (II) influence gene expression in the vagal jugular and nodose ganglia in a manner that can lead to relevant phenotypic changes in the airway sensory nerves. (III) Action potentials arriving in the brainstem are integrated, ultimately leading to sensations and to (IV) increases in preganglionic parasympathetic drive. (V) This will increase neurotransmission at the neuro-effector junctions, causing bronchoconstriction and mucus secretion; effects further amplified by inhibition of inhibitory muscarinic autoreceptors. See text for references