Endomorphin 2

Endomorphins are recently discovered endogenous opioid peptides composed of four amino acids: Endomorphin-1 (EM-1) is Tyr-Pro-Trp-Phe-NH2, and  Endomorphin-2 (EM-2) is Tyr-Pro-Phe-Phe-NH2. These peptides have a very high affinity and specificity for mu-opioid receptors as it has been reported in many pharmacological studies. EM-1 is distributed in many brain regions, whereas EM-2 is prevalent in brainstem and spinal cord.  EM-1 and EM-2 exert their antinociceptive activity by interacting with mu-opioid receptors. EM-1 anf EM-2 bind with mu-opioid receptor with high affinity and selectivity in comparison with binding to opioid delta and kappa receptors. EM-1 and EM-2 tetrapeptides activate G-proteins and inhibit adenylyl cyclase activity when bind to mu-opioid receptors.

Image: Endomorphin-2 Staining in rat dorsal horn.

Note: Our affinity-purified anti END-1 antibody  label neuronal fibers in various brain regions including (but not limited to) thalamic nuclei, periaqueductal gray matter, amygdala, locus coeruleus, nucleus accumbens, parabrachial nucleus, nucleus tractus solitarius and septum. Our affinity-purified anti EM-2 antibodies label neuronal processes in spinal cord dorsal horn and trigeminal tract, and label neuronal cell bodies in thalamus. END-1 and 2 distribution in brain overlaps with mu-opioid receptors.

Image: END-2 staining of neurons from neonatal rat lumbar (L4/5) DRG. doi: 10.1111/j.1460-9568.2008.06238.x.