DSIP reduces amphetamine-induced hyperthermia in mice.

The effects of delta sleep-inducing peptide (DSIP) have not been fully determined. Besides sleep-inducing activities, effects on locomotor behavior, stress-reduction, and temperature-regulation have been published. It was reported that DSIP reversed the increase in temperature of rats injected at room temperature with 15 mg d-amphetamine per kg body weight. We examined this effect in mice with 9 different concentrations of DSIP in addition to D-Ala4-DSIP and an analog, DSIP-P, phosphorylated at the serine in position 7. A reduction of the increased temperature was observed in mice but not in rats. This effect was only significant after pretreatment with 0.1 and 150 nmol DSIP/kg, but not the other doses. D-Ala4-DSIP decreased the rise in temperature between 50-150 nmol/kg, but DSIP-P showed no such effect nor was DSIP able to significantly reduce the increase of temperature induced by the larger dose of 30 mg/kg d-amphetamine. A bell-shaped dose-response curve was found for D-Ala4-DSIP; for DSIP two active dose ranges were observed. Thus, complex dose-effect relationships seem to exist for DSIP (and perhaps its analogs) in thermoregulation.