Protons as Intercellular Messengers

Muscle contractions are driven by neurotransmitters released at neuromuscular junctions. In this issue, report that protons, in the absence of neurotransmitters and neurons, can stimulate muscle contractions involved in the defecation cycle of the worm Caenorhabditis elegans. Their results identify protons as a new intercellular messenger and suggest that proton-mediated intercellular communication may be a widespread phenomenon.