The atrial gland peptide A and peptide B precursors are the source of the 2 peptides that, upon release from this reproductive system gland, initiate the egg-laying process by exciting the bag cell neurons. These neurons, clustered in neural connectives near the abdominal ganglion, in turn release other peptides that act directly on the ganglion and also, via the circulating hemolymph, on many other organs to control the physiological processes of egg-laying. One of these other peptides is the egg-laying hormone. Injected in sexually mature animals califin A excites LB and LC cells of the abdominal ganglion and causes egg-laying. Califin A consists of a 36-residue large subunit bound by a single disulfide bond to a 18-residue small subunit. Belongs to the molluscan ELH family.