Maderspach K, Solomonia R
Institute of Biochemistry, Hungarian Academy of Sciences, Szeged.
Brain Res. 1988 Feb 16;441(1-2):41-7. doi: 10.1016/0006-8993(88)91381-9.
Opioid receptors were characterized in glial and neuronal homogeneous cultures of embryonic chick forebrain, using [3H]naloxone as a labelled ligand. Binding experiments were performed on intact cells. The specific binding of [3H]naloxone reached equilibrium after 1 min. The apparent dissociation constants were estimated as 0.51 nM for glial and 0.63 nM for neuronal cells. Equilibrium measurements indicated the apparent positive cooperativity of the binding, resulting in Hill coefficients of 2.61 for glial and 2.04 for neuronal cells. Competition of unlabelled naloxone for specific binding sites resulted in maximum-shape curves in glial cells if measured at low receptor occupancy. This supports the positive cooperativity of ligand binding. Opioid agonists, ethylketocyclazocine (EKC), morphine and [D-Ala2,L-Leu5]enkephalin (DALA), provoked biphasic competition curves in both cell types with a characteristic maximum at low competitor concentrations. The possible physiological role of glial opioid receptors in neuron-glia communication and the significance of cooperativity is discussed.
利用[3H]纳洛酮作为标记配体，在胚胎鸡前脑的胶质细胞和神经元均质培养物中对阿片受体进行了表征。在完整细胞上进行结合实验。[3H]纳洛酮的特异性结合在1分钟后达到平衡。胶质细胞的表观解离常数估计为0.51 nM，神经元细胞为0.63 nM。平衡测量表明结合具有明显的正协同性，导致胶质细胞的希尔系数为2.61，神经元细胞为2.04。如果在低受体占有率下测量，未标记的纳洛酮对特异性结合位点的竞争在胶质细胞中产生最大形状曲线。这支持了配体结合的正协同性。阿片类激动剂，乙基酮环唑辛（EKC）、吗啡和[D-Ala2，L-Leu5]脑啡肽（DALA），在两种细胞类型中均引发双相竞争曲线，在低竞争者浓度下具有特征性最大值。讨论了胶质阿片受体在神经元-胶质细胞通讯中的可能生理作用以及协同性的意义。
