Cardioactive peptide. Corazonin is probably involved in the physiological regulation of the heart beat. Clock (Clk) and cycle (cyc) proteins negatively regulate Crz transcription in a cell-specific manner. From late embryo to larva, expression is consistently detected in three neuronal groups: dorso-lateral neurons (DL), dorso-medial neurons (DM), and neurons in the ventral nerve cord (vCrz). Both the vCrz and DM groups die via programmed cell death during metamorphosis, whereas the DL neurons persist to adulthood. In adults, expression is seen in a cluster of six to eight neurons per lobe in the pars lateralis (DLP), in numerous neuronal cells in the optic lobes, and in a novel group of four abdominal ganglionic neurons present only in males (ms-aCrz). Projections of the ms-aCrz neurons terminate within the ventral nerve cord, implying a role as interneurons. Terminals of the DLP neurons are found in the retrocerebral complex that produces juvenile hormone and adipokinetic hormone, located in the vicinity of terminals emanating from PDF-containing pacemaking neurons. Belongs to the corazonin family.