Eledoisin is an undecapeptide of mollusk origin, belonging to the tachykinin family of neuropeptides.

These peptides exhibit a wide and complex spectrum of pharmacological and physiological activities such as vasodilation, hypertension, and stimulation of extravascular smooth muscle.

"Xxx" is either an aromatic (phenylalanine, tyrosine) or a branched aliphatic (valine, isoleucine) side chain and is thought to be important in receptor selectivity.

This common region, often referred to as the "message domain," is believed to be responsible for activating the receptor.

The divergent N-terminal region or the "address domain" varies in amino-acid sequence and length and is believed to play a role in determining the receptor subtype specificity.