Delta (Phospho) Sleep Inducing Peptide

Delta (Phospho) Sleep Inducing Peptide (DSIP-P) is a phosphorylated synthetic analog of the endogenous sleep-regulating neuropeptide DSIP at the serine residue at position 7. Delta (Phospho) Sleep Inducing Peptide is a peptide with prolonged sleep-promoting effects and can induce changes in the circadian locomotor behavior in rats.

Method: Rat pineal glands were cultured in Richter's medium for 48 h, then incubated with Delta (Phospho) Sleep Inducing Peptide (0.2–2000 nM) together with norepinephrine (NE, 10⁻⁶ M) for 4 h, followed by measurement of N-acetyltransferase (NAT) activity.
Result: Delta (Phospho) Sleep Inducing Peptide at a concentration of 2 nM significantly enhanced NE-induced NAT activity, increasing NAT activity by nearly 100% [1].

Method: Female rats were adapted to a 12 hr light-dark cycle (lights on 6:00–18:00) and then injected intravenously with Delta (Phospho) Sleep Inducing Peptide (0.1 nmol/kg) in the late afternoon (17:30–18:00) daily for 4 consecutive days. Circadian locomotor activity rhythms were monitored using an Animex activity recorder.
Result: Delta (Phospho) Sleep Inducing Peptide affected the rat's daily activity pattern on the first day of injection, and a stable new activity rhythm was established by the third day, which was opposite to the external light-dark cycle (Zeitgeber). This was manifested as reduced activity during the dark phase (night) and relatively increased activity during the light phase (day), indicating a relative reversal or shift of the circadian rhythm [2].
Method: Male rats (Sprague-Dawley) were injected with Delta (Phospho) Sleep Inducing Peptide (20 or 200 pmol/kg) into the third cerebral ventricle just before the onset of the dark phase under a 12:12 hr light-dark cycle. Sleep phases were recorded and analyzed for 48 hours post-injection using electroencephalography (EEG) and electromyography (EMG).
Result: Delta (Phospho) Sleep Inducing Peptide (200 pmol/kg) increased slow-wave sleep (SWS, +17.3%) and paradoxical sleep (PS, +32.3%) during the dark phase without shortening sleep latency. The SWS-promoting effect persisted into the following light phase and returned to control levels by the second day [3].