Garzón J, Castro M, Sánchez-Blázquez P
Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas, C/Dr Arce 37, 28002 Madrid, Spain.
Eur J Neurosci. 1998 Aug;10(8):2557-64. doi: 10.1046/j.1460-9568.1998.00267.x.
The affinity displayed by different opioids to mu receptors (ORs) was determined in mouse brain membranes incubated with antibodies directed to Galpha subunits of the guanine nucleotide-binding proteins Gi2 and Gz. Assays were conducted with 10 pm 125I-Tyr27-beta-endorphin in the presence of 300 nm N, N-diallyl-Tyr-(alpha-aminoisobutyric acid)2-Phe-Leu-OH (ICI-174 864), which prevented the binding of the iodinated neuropeptide to delta-ORs. Gpp(NH)p or the preincubation of mouse brain membranes with IgGs to Gi2alpha or Gzalpha subunits, promoted reductions in the affinity exhibited by the labelled probe. The potencies of beta-endorphin, [D-Ala2,N-MePhe4,Gly-ol5]-enkephalin (DAMGO) and [D-Pen2,5]enkephalin (DPDPE) were reduced after impairing the coupling of mu-ORs to Gi2 or Gz proteins. Morphine showed a loss of affinity towards the mu-OR after preincubation of membranes with IgGs to Gzalpha subunits. However, it retained its potency after treatment with the anti-Gi2alpha IgGs. Conversely, [D-Ala2, D-Leu5]enkephalin (DADLE) and [D-Ser2, Leu5] enkephalin-Thr6 (DSLET) showed decreased affinity to mu-ORs after treatment with anti-Gi2alpha IgGs, with no noticeable change following the use of IgGs to Gzalpha subunits. The affinity exhibited by the opioid antagonists naloxone, naltrexone, naloxonazine and [Cys2,Tyr3,Orn5, Pen7 amide]somatostatin analogue (CTOP) remained unchanged after either treatment. Therefore, the affinity exhibited by opioid agonists of mu-ORs, but not antagonists, depends on the nature of the G-protein coupled to these receptors.
在与针对鸟嘌呤核苷酸结合蛋白Gi2和Gz的Gα亚基的抗体一起孵育的小鼠脑膜中，测定了不同阿片类药物对μ受体（ORs）的亲和力。在300 nM N，N-二烯丙基-Tyr-（α-氨基异丁酸）2-Phe-Leu-OH（ICI-174 864）存在的情况下，用10 pm 125I-Tyr27-β-内啡肽进行测定，该物质可防止碘化神经肽与δ-ORs结合。Gpp（NH）p或用针对Gi2α或Gzα亚基的IgG对小鼠脑膜进行预孵育，会促使标记探针所表现出的亲和力降低。在破坏μ-ORs与Gi2或Gz蛋白的偶联后，β-内啡肽、[D-Ala2，N-MePhe4，Gly-ol5]-脑啡肽（DAMGO）和[D-Pen2，5]脑啡肽（DPDPE）的效力降低。在用针对Gzα亚基的IgG对膜进行预孵育后，吗啡对μ-OR的亲和力丧失。然而，在用抗Gi2α IgG处理后，它仍保留其效力。相反，在用抗Gi2α IgG处理后，[D-Ala2，D-Leu5]脑啡肽（DADLE）和[D-Ser2，Leu5]脑啡肽-Thr6（DSLET）对μ-ORs的亲和力降低，在用针对Gzα亚基的IgG处理后没有明显变化。在用任何一种处理后，阿片类拮抗剂纳洛酮、纳曲酮、纳洛嗪和[Cys2，Tyr3，Orn5，Pen7酰胺]生长抑素类似物（CTOP）所表现出的亲和力保持不变。因此，μ-ORs的阿片类激动剂而非拮抗剂所表现出的亲和力取决于与这些受体偶联的G蛋白的性质。
