Figure 5.

Schematic illustration of the contribution of gas neuromodulators to carotid body chemosensory function in CHF. In normal normoxic conditions, both NO and CO exert inhibitory effects (dashed lines) on carotid body chemoreceptor (glomus) cell excitability, which in turn tempers the release of excitatory neurotransmitters at post-synaptic petrosal ganglion nerve endings to limit afferent neural discharge. By contrast, H₂S exerts an excitatory effect (solid line), which is manifested during hypoxia. In CHF, chronic downregulation of NO and CO production disinhibits excitatory influences on chemoreceptor excitability to elevate carotid body afferent discharge under both normoxic and hypoxic conditions. See Schultz (2011) for description of effects mediated by reactive oxygen species (ROS).