DSIP-like immunoreactivity in the developing rat brain

Delta sleep-inducing peptide (DSIP) is a naturally occurring nonapeptide that has been reported to affect sleep. The concentration of DSIP-like material was measured by a highly specific radioimmunoassay in brain tissue from developing rats. DSIP-like immunoreactivity was present in fetal brain at increased levels shortly before birth. In one experiment, a significant elevation in the concentration of the peptide occurred at postnatal day 20, but in a second, similar, study the increase occurred later. No marked differences in the levels of DSIP-like immunoreactivity were found in the brains of rats injected 2 months earlier with DSIP or among 10 parts of brains obtained at postnatal day 20. Regardless of the function of DSIP, it is available to the rat throughout early development.