Proctolin

Proctolin, RYLPT, the first insect neuropeptide, was isolated from the cockroach Periplaneta americana. This peptide is synthesized in the central nervous system of several insect species and arthropods and it was originally considered as a visceral muscle neurotransmitter. It later became apparent that proctolin also acts as a neuromodulator affecting myogenic muscle activity or neurally evoked contractions on visceral and skeletal muscles.