the intrathecal administration of several mu ( morphine ) , delta ( d-ala2-d-leu5-enkephalin , dimeric leu-enkephalin ) and mixed mu/delta ( beta-endorphin ) agonists produced a dose-dependent inhibition of all cutaneous thermal ( tail flick/hot plate ) nociceptive responses in the rat .
C0014298
enkephalin
C0014294
leu-enkephalin