DSIP (Delta Sleep-Inducing Peptide) vs Oxytocin

DSIP (Delta Sleep-Inducing Peptide)

DSIP, or delta sleep-inducing peptide, is a nine-residue peptide first described in rabbits during experimentally induced sleep. It was isolated from blood drawn from animals in which sleep had been produced by electrical stimulation of the brain, and the name comes from the slow-wave activity reported when that material was transferred to other animals. Later studies in animals and small human studies gave inconsistent findings on sleep, and the name describes how the peptide was found rather than an agreed function. No gene encoding DSIP and no dedicated receptor have been found. Work continued on its possible roles in stress hormones and other systems, but the literature is fragmented, and much of it is several decades old.

Oxytocin

Oxytocin is a nine-residue peptide hormone, cyclised by a disulphide bond between its two cysteines and amidated at the C-terminus. It is made by neurons of the hypothalamus and released both from the posterior pituitary into the circulation and within the brain. It differs from vasopressin at two of its nine positions, and their receptors belong to one family. Its classical physiological roles, in uterine contraction and milk ejection, were established first, and in the 1950s it became the first peptide hormone to be synthesised in the laboratory. More recent research concerns its signalling in the brain and social behaviour; the animal literature is substantial, while human findings have been inconsistent and remain debated.

How DSIP (Delta Sleep-Inducing Peptide) acts

Without an identified receptor or gene, DSIP's standing as a signalling molecule in its own right is uncertain, and its mechanism is described through scattered observations. Animal and tissue studies have reported interactions with GABA and glutamate transmission, including NMDA receptors, with opioid signalling, and with the hypothalamic–pituitary–adrenal axis, where release of ACTH and corticosterone has been examined. Immunoreactive material resembling DSIP has been reported in the brain and in peripheral tissues. These reports come from different models and methods, and no single pathway has emerged that ties them together.

How Oxytocin acts

The oxytocin receptor (OXTR) is a class A G-protein-coupled receptor that signals mainly through Gq/11, activating phospholipase C and raising intracellular calcium; coupling to other G proteins has also been reported. It is expressed in the myometrium, mammary myoepithelial cells and several brain regions, among other tissues, and uterine expression rises sharply late in pregnancy. Because oxytocin and vasopressin are so alike, each can act at the other's receptors at higher concentrations, and oxytocin has measurable activity at the vasopressin V1a receptor. How much oxytocin in the circulation crosses into the brain is still debated.

The records side by side

• Type: DSIP (Delta Sleep-Inducing Peptide), Nonapeptide; Oxytocin, Cyclic nonapeptide hormone (neurohypophysial peptide)
• Length: DSIP (Delta Sleep-Inducing Peptide), 9 amino acids; Oxytocin, 9 amino acids
• Molecular weight: DSIP (Delta Sleep-Inducing Peptide), 848.8 g/mol; Oxytocin, 1007.2 g/mol
• Molecular formula: DSIP (Delta Sleep-Inducing Peptide), C35H48N10O15; Oxytocin, C43H66N12O12S2
• Half-life: DSIP (Delta Sleep-Inducing Peptide), not recorded; Oxytocin, Plasma half-life of oxytocin ranges from 3 to 20 min.

Reading a comparison

A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.