adrenorphin (metorphamide) is a potent inhibitor of nicotine-induced adrenaline and noradrenaline release with ic50 value of 10 μm [1].adrenorphin (metorphamide) is an endogenous, c-terminally amidated, opioid octapeptide (tyr-gly-gly-phe-met-arg-arg-val-nh2) that is produced from proteolytic cleavage of proenkephalin a and is widely distributed throughout the mammalian brain [2].adrenorphin (metorphamide) is selective nicotine-induced adrenaline and noradrenaline release inhibitor and has higher than 100-fold more potent than the reported nicotine-induced adrenaline and noradrenaline release inhibitor met5-enkephalin. when tested with bovine adrenal chromaffin cells, adrenorphin (metorphamide) showed inhibition on 5 μm nicotine-induced atp release by almost 50% at 5μm and the inhibition was not in a dose-dependent manner [1]. in bioassays and binding assays, metorphamide exhibited high μ-binding activity, as well as κ-binding activity with nearly half percent toμ-binding activity, while showed no activity on δ-binding [2].
[1]. marley, p.d., k.i. mitchelhill, and b.g. livett, metorphamide, a novel endogenous adrenal opioid peptide, inhibits nicotine-induced secretion from bovine adrenal chromaffin cells. brain res, 1986. 363(1): p. 10-7.
[2]. weber, e., et al., metorphamide: isolation, structure, and biologic activity of an amidated opioid octapeptide from bovine brain. proc natl acad sci u s a, 1983. 80(23): p. 7362-6.
