Interactions between the antiopiate Tyr-MIF-1 and the mu opiate morphiceptin at their respective binding sites in brain.
The interactions between Tyr-MIF-1, a brain peptide with antiopiate activity, and the beta-casomorphins, a family of peptides derived from milk protein with opiate activity, were investigated by in vitro binding assays. Specific binding of 125I-Tyr-MIF-1 to rat brain membranes was displaced with high potency by beta-casomorphin, morphiceptin, and the morphiceptin analog PL017 but not by the analgesically inactive analog D-Pro2-morphiceptin or by several other ligands for classical delta, kappa, or sigma opiate receptors. In addition, Tyr-MIF-1 displaced 125I-morphiceptin from its binding sites in brain with affinities similar to those of unlabeled morphiceptin and PL017. These results, which include the first demonstration of a binding site in brain for labeled morphiceptin, indicate that brain antiopiate Tyr-MIF-1 and the beta-casomorphin derived peptides with opiate activity may share a common binding site or cross-react at each other's site. This suggests a possible mechanism of action for endogenous antiopiate-opiate interactions.
Zadina
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JE
Kastin
A J
AJ
D000700:Analgesics / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D004723:Endorphins / Q000378:metabolism*; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D009270:Naloxone / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000378:metabolism*; D017450:Receptors, Opioid, mu
D000700:Analgesics; D004723:Endorphins; D007457:Iodine Radioisotopes; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D009270:Naloxone; C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone; C028889:morphiceptin