male icr mice were rendered tolerant by intrathecal ( it ) injection once a day with either mu-agonist , d-ala2-nmephe4-gly-ol-enkephalin ( damgo ) or delta-agonist , d-pen2-d-pen5-enkephalin ( dpdpe ) ( toleragen ) by doubling the dose each day starting from 0.125 and 1 microgram for damgo and dpdpe , respectively , for 6 days .
C0014298
enkephalin
C0525856
dpdpe