Met-Enkephalin (trifluoroacetate salt)

Met-Enkephalin is an endogenous neuropeptide involved in nociception and an agonist of δ- and µ-opioid receptors (Kis = 0.65 and 1.7 nM, respectively). It is selective for δ- and µ- over κ-opioid receptors (Ki = >1,000 nM). Met-Enkephalin is a cleavage product of proenkephalin, which is found primarily in the adrenal medulla and the CNS. Met-Enkephalin is found in the brain, primarily in the globus pallidus, nucleus accumbens, and substantia nigra, the brainstem, and the spinal cord as well as in the peripheral nervous system. Met-Enkephalin has antinociceptive effects in mouse models of acute pain, including tail pressure, hot plate tail-flick, and acetic acid-induced writhing tests (ED50s = 170, 140, and 88 nmol/animal, respectively). Levels of Met-enkephalin are increased at the site of inflammation in a complete Freund's adjuvant mouse model of chronic inflammatory pain.