A short‑term study showed that the sleep‑promoting peptide DSIP quickly changes several immune signaling proteins (cytokines) in the blood, more so than 5‑HTP or serotonin. These changes happen within minutes, before any noticeable sleep or physical effects.

Short term effects of the sleep promoting substances DSIP, 5-HTP and 5-HT on the function of the lymphokine system were studied 10 and 30 min after treatment. DSIP treatment after 10 and 30 min caused a significant decrease in IL-3 and CSF levels, response to CSF-1 and CSF-GM, IL-2 level, number of IL-2 receptors and in cell proliferation. DSIP initially induced (after 10 min) a decrease to be followed (after 30 min) by an increase in IL-1 level. Ten minutes after 5-HTP treatment a decrease was found in all parameter tests, except in IL-3 and in CSF secretion. 5-HT treatment was able to induce an increase in IL-3 level, a decrease in response to IL-2 receptors and proliferation, 10 min after treatment. Thirty minutes after treatment, only IL-3 and IL-2 levels were reduced. These results showed that sleep promoting substances had an effect on the lymphokines system, that DSIP was the most potent agent, that immunological changes occur before physiological or behavioral signs. The relative weak potency 5-HTP and 5-HT, and the similar pattern of effects between them, may indicate that peripheral events may lead to sleep state.