Brown G P, Pasternak G W
Cotzias Laboratory of Neuro-Oncology, Cornell U. Medical College, New York, New York, USA.
J Pharmacol Exp Ther. 1998 Jul;286(1):376-81.
Naloxone benzoylhydrazone (NalBzoH) is a potent mu antagonist in vivo. In a cell line stably transfected with MOR-1 (CHO/MOR-1), NalBzoH also was an antagonist when examined in adenylyl cyclase studies. In binding studies, it displayed high affinity for the mu receptor, confirming its earlier characterization in brain membranes. In competition studies under equilibrium conditions, NalBzoH and diprenorphine both retained their potency in the presence of the stable GTP analog 5'-guanylylimidophosphate, consistent with their mu antagonist properties, whereas the agonist DAMGO showed more than a 3-fold loss of affinity. The dissociation of 3H-diprenorphine was monophasic. However, kinetic studies revealed biphasic dissociations for both 3H-NalBzoH and 3H-DAMGO. The slow component of 3H-NalBzoH dissociation, corresponding to the higher affinity state, was dependent on coupling to G-proteins. It is selectively abolished by guanine nucleotides, leaving only the rapid dissociation phase. Furthermore, the slow dissociation component is eliminated by treatment of the cells with pertussis toxin, but not cholera toxin. In conclusion, NalBzoH is an unusual opioid. Functionally it is an antagonist, a classification consistent with its equilibrium binding in the presence of guanine nucleotides. Yet, kinetic studies reveal that it labels a G-protein coupled state of the receptor with high affinity.
纳洛酮苯甲酰腙（NalBzoH）在体内是一种强效的μ受体拮抗剂。在稳定转染了MOR-1的细胞系（CHO/MOR-1）中，在腺苷酸环化酶研究中检测时，NalBzoH也是一种拮抗剂。在结合研究中，它对μ受体显示出高亲和力，证实了其在脑膜中的早期特性。在平衡条件下的竞争研究中，NalBzoH和二丙诺啡在稳定的GTP类似物5'-鸟苷酰亚胺磷酸存在下均保持其效力，这与其μ拮抗剂特性一致，而激动剂DAMGO的亲和力损失超过3倍。3H-二丙诺啡的解离是单相的。然而，动力学研究显示3H-NalBzoH和3H-DAMGO的解离均为双相。3H-NalBzoH解离的慢成分对应于较高亲和力状态，依赖于与G蛋白的偶联。它被鸟嘌呤核苷酸选择性消除，仅留下快速解离阶段。此外，通过用百日咳毒素处理细胞可消除慢解离成分，但霍乱毒素则不能。总之，NalBzoH是一种不同寻常的阿片类药物。在功能上它是一种拮抗剂，这一分类与其在鸟嘌呤核苷酸存在下的平衡结合一致。然而，动力学研究表明它以高亲和力标记受体的G蛋白偶联状态。
