Proctolin is a pentapeptide. It was the first myotropic insect neuromodulator to be structurally characterized. Proctolin is detected in different parts of the insect body such as the central nervous system and digestive tract, and in the brain of other invertebrates. Proctolin is found to significantly increase the synthesis and release of juvenile hormone (JH) from locust corpus allatum (CA), with the increase being greatest from CAs that have a relatively low basal rate of JH biosynthesis.