Inhibition of opiate receptor binding by zinc ions: possible physiological importance in the hippocampus.
In the rat and guinea pig hippocampus, the staining pattern for enkephalin (by immunocytochemistry) and for zinc (by the Timm method) is congruent and confined to the mossy fiber system. The stereospecific binding of 3H-enkephalinamide (2-D-Ala-5-L-methionine) to opiate receptors can be totally blocked by zinc ions, both in the hippocampus and in the cerebral cortex, the basal ganglia and the rest of the forebrain. Scatchard analysis of binding isotherms indicates that this inhibitory effect involves a decrease in receptor affinity, whereas the number of binding sites is unaffected. Thiol reductants can reactivate Zn2+-inhibited opiate receptors with a potency correlating to their redox potential (Eo). Thus, our data suggest that zinc ions represent modulators of opiate receptor binding in the hippocampus and that they work through a redox reaction with essential SH-groups of opiate receptors.
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D006168:Guinea Pigs; D006624:Hippocampus / Q000502:physiology*; D008670:Metals / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D013237:Stereoisomerism; D015032:Zinc / Q000494:pharmacology*
D008670:Metals; D011957:Receptors, Opioid; D015032:Zinc