In stressed rats, giving the peptide DSIP (delta‑sleep inducing peptide) raised levels of a brain chemical called substance P, reduced stress‑related changes in the adrenal glands and thymus, and helped more rats survive emotional stress. Both a single shot and a series of five shots worked, with effects seen a few hours after injection.

In the work was studied the effect of the delta-sleep inducing peptide (DSIP) on the substance P (SP) content in the hypothalamus of August rats genetically predisposed to emotional stress. The hypothalamic SP level increased 3 h and 6 h after systemic i. p. DSIP administration in doses of 60 and 120 nM/kg. The effects of i. p. DSIP administration on the hypothalamic SP were studied on an experimental model of aggressive-conflict behaviour in rats. The peptide was injected before the animals were exposed to stress. Quintuple DSIP administration in the above mentioned doses before exposing rats to stress induced highly significant increase in the hypothalamic SP. Single DSIP injections also significantly elevated SP values, reduced the adrenal hypertrophy and the thymus involution resulting in an increase of the rats' survival as compared to the control animals exposed to stress without DSIP. The antistressor effect of DSIP is assumed to be realized through the increase of the hypothalamic SP which is a factor enhancing the animal resistance to emotional stress.