Delta Sleep-Inducing Peptide (DSIP) is an endogenous nonapeptide (Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu) originally isolated from cerebral venous blood of sleeping rabbits. This neuropeptide plays a crucial role in regulating sleep architecture, particularly slow-wave sleep (SWS), while also demonstrating significant neuroprotective, anti-stress, and analgesic properties. Beyond its primary sleep-inducing effects, DSIP modulates multiple neuroendocrine systems, influences circadian rhythms, and protects against various forms of physiological stress, making it a valuable tool for neuroscience and sleep research.