Cholera toxin, cyclic AMP, and the firefly flash

Cholera toxin, injected into living fireflies, caused a delayed, non-hormone-dependent activation of adenylate cyclase, an elevation of cyclic AMP levels, and a brilliant persistent glow of the firefly light organ 8-20 hours following injection. During periods of spontaneous flashing, onset of toxin-induced glowing was abrupt and step-like in character, due to a markedly prolonged off-time of individual flashes. These observations provide a striking demonstration of the mechanism of cholera toxin action, and, together with other data, suggest that the initiation of the normal adult firefly flash is mediated through elevation of cyclic AMP levels secondary to the activation of an octopamine-sensitive adenylate cyclase.