Pharmacological control of ciliary activity in the young sea urchin larva: chemical studies on the role of cyclic nucleotides.

Distinct peaks in cAMP and cGMP content during early development, partly opposite to each other, may be correlated with the two main phases of gastrulation and ciliary activity. Monoamines increases cAMP formation. A transient or extended decrease follows, presumably reflecting some feedback mechanism. Muscarinic agents and Ca2+ interfere. The developmental variation in cyclic nucleotides may reflect a temporal shift in the role of various signal substances as well as feedback regulation related to Ca2+ influx. The opposite changes in cAMP and cGMP during early gastrulation may reflect a mutual dependency of the two nucleotide cyclases related to changes in Ca2+ influx.