DSIP

Details:

Delta Sleep-Inducing Peptide (DSIP) is a naturally occurring nonapeptide, originally isolated from rabbit brain, that promotes sleep, and is synthesized in the hypothalamus, readily absorbed from the gut, and crosses the blood-brain barrier easily. 
Here's a more detailed look at DSIP:
Discovery and Origin:
DSIP was first isolated from rabbit brain in 1977. 
Structure:
It's a nonapeptide with the amino acid sequence: Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu. 
Function:
DSIP promotes sleep by targeting various areas of the brain and influences the circadian rhythm. 
Mechanism of Action:
The exact mechanism by which DSIP promotes sleep is still not fully understood, but it is known to cross the blood-brain barrier easily and is not denatured by enzymes. 
Potential Therapeutic Uses:
DSIP has been investigated for its potential in treating insomnia, pain, and withdrawal symptoms. 
Other Effects:
DSIP has been observed to affect electrophysiological activity, neurotransmitter levels, circadian and locomotor patterns, hormonal levels, psychological performance, and the activity of neuropharmacological drugs. 
DSIP and Disease:
Low concentrations of DSIP have been observed in patients with schizophrenia and depression. 
DSIP has been found to have anticarcinogenic and geroprotective effects. 
Studies have demonstrated a direct link between GILZ expression (homologous to DSIP) and adipogenesis which has links to obesity and metabolic syndrome. 
In studies on rats with metaphit-induced epilepsy DSIP acted as an anticonvulsant. 
DSIP has been found to have an analgesic effect. 
DSIP and Bacterial Alignment:
A Basic Local Alignment Search Tool (BLAST) search of the peptide sequence showed that it aligned with a hypothetical protein in Amycolatopsis coloradensis and with other pseudogenes or putative proteins in other bacterial species.