The alpha-1 peptide acts as an osmoregulatory peptide, increasing blood volume, and also modulates the activity of a set of cardiac motor neurons that control heart rate. A number of isoforms are produced. Expressed within the abdominal ganglion in neurons R15, RB(HE), the two L9(G) gill motoneurons, and L40 interneuron, all are parts of autonomic control circuit that contributes to implementing a central command to coordinate autonomic activity with escape locomotion. R15 alpha-1. R15 alpha-2. Isoform R15-1 produces peptide R15 alpha-2 which is a 24 aa long spliced form of peptide R15 alpha-1 which is produced by isoform R15-2.