Delta-sleep-inducing Peptide (DSIP) Stimulates the Release of Immunoreactive Met-enkephalin from Rat Lower Brainstem Slices in Vitro

We studied whether delta-sleep-inducing peptide (DSIP) acted on opioid receptor directly or indirectly. DSIP did not have binding activity to any subtype of opioid receptors. DSIP at doses of 1 pM-1 nM significantly stimulated the release of immunoreactive Met-enkephalin (iME) from superfused slices of the rat lower brainstem. The DSIP-induced release of iME was calcium-dependent. These results show that DSIP acts on opioid receptor indirectly by stimulating the release of iME in producing antinociceptive effects.