Figure 1.

Acute exposure of Caenorhabditis elegans to elevated CO₂ level causes animal avoidance and stops pharyngeal muscle contractions. Both responses are regulated by the BAG neurons but through separate signaling pathways. While avoidance requires cGMP signaling, the inhibition of muscle contraction in the pharynx is mediated by neuropeptide secretion. Both CO₂ responses are decreased following starvation.