two approaches were used at supraspinal and spinal sites : determination of possible cross-tolerance between morphine and a variety of receptor selective/nonselective agonists ( dpdpe , [ d-pen2 , l-pen5 ] enkephalin ( dplpe ) , [ d-ala2 , mephe4 , gly-ol ] enkephalin , [ d-ala2 , met5 ] enkephalin amide , [ d-ser2 , leu5 , thr6 ] enkephalin and [ d-thr2 leu , thr6 ] enkephalin ) and possible potentiation of morphine ( mu ) analgesia by proposed delta agonists ( dpdpe , dplpe and [ d-ala2 , d-leu5 ] enkephalin ) in naive and morphine-tolerant mice .
C0525856
dpdpe
C0014298
enkephalin