Delta-sleep-inducing peptide (DSIP) is an endogenous substance that regulates the response of the organism to stress. It was found that DSIP, like diazepam and ethanol, activates muscimol-stimulated 36Cl- uptake in the rat brain cortex and partially counteracts the stimulatory action of ethanol on this process. The effect of peptide disappears at the lowering of the incubation temperature. We propose that DSIP is a concordant regulator partly mediating its action through the membrane phospholipids.