Egg-laying hormone (ELH) is a neuropeptide synthesized by the bag cell neurons, Egg-laying hormone (ELH) induces egg laying and its correlated behavior in Aplysia californica. Egg-laying hormone (ELH) has been purified to homogeneity and Egg-laying hormone (ELH)'s primary structure has been determined. Egg-laying hormone (ELH) have 36 amino acid residues with a Mr of 4385 and a calculated isoelectric point of 9.7. Egg Laying Hormone of Aplysia induces a voltage-dependent slow inward current carried by Na+ in an identified motoneuron.