Table 2 A synthesis of how zinc ions modulate the interactions between opioid receptors ligands and their receptors is presented below
type of ligand | endogenous / exogenous (for agonists) | name | receptor | effects | brain structure | concentration | reference | ||
|---|---|---|---|---|---|---|---|---|---|
zinc ion actions | agonists | endogenous | enkephaline | δ-receptor specific agonist | reduced both affinity and number of binding sites | physiological concentration | Ogawa N. et al., 1985 [43] | ||
exogenous | [3H] DAGO [([Tyr-D-Ala-Gly-Methyl-Phe-Glyol]-enkephalin | μ-receptor | reduced | micromolar concentration | Tejwani G.A., Hanissian S.H. 1990 [42] | ||||
μ-receptor | reduced | Fowler C.B. et al., 2004 [78] | |||||||
[3H] DSTLE ([Tyr-D-Ser-Gly-Phe-Leu-Thr]-enkephalin) | δ-receptor | slighly reduced | micromolar concentration | Tejwani G.A., Hanissian S.H. 1990 [42] | |||||
3H-met-enkephalinamide (2-D-ala-5-L-methionine) | δ-receptor | reduced | hippocampus, the cerebral cortex and the basal ganglia of the (rat) | endogenous concentrations | Stengaard-Pedersen K., 1982 [79] | ||||
[3H] EKC (ethylketocyclazocine) | κ-receptor | slighly reduced | micromolar concentration | Tejwani G.A., Hanissian S.H. 1990 [42] | |||||
(+)-[3H]pentazocine | σ2-receptor | slighly reduced | hippocampus (rat) | milimolar concentration | Connor M.A., Chavkin C. 1992 [83] | ||||
antagonist | [3H]naloxone | μ-receptor | reduced affinity, with no effect on the number of binding sites | hippocampus, cortex, midbrain, striatum (rat) | dose-dependent manner | Hanissian S.H., Tejwani G.A. 1990 [85] | |||
reduced zinc concentration compared to physiologic conditions | metallothionein peptide 1 (specific zinc chelator) | agonists | exogenous | (+)-[3H]pentazocine | σ2-receptor | non-changed | hippocampus (rat) | Connor M.A., Chavkin C. 1992 [83] | |
zinc deficiency effect compared to normally-fed animals | antagonist | [3H]naloxone | μ-receptor | increased | isolated brain membranes (rat) | Essatara M.B., 1984 [72] | |||