Pasquini F, Bochet P, Garbay-Jaureguiberry C, Roques B P, Rossier J, Beaudet A
Montreal Neurological Institute, McGill University, Quebec, Canada.
J Comp Neurol. 1992 Dec 8;326(2):229-44. doi: 10.1002/cne.903260206.
The distribution of delta opioid receptors, selectively labelled in vitro with the photoaffinity probe monoiodo azido-DTLET ([D-Thr2,pN3Phe4, Leu5]enkephaly-Thr6), was analyzed by light and electron microscopic radioautography in sections from rat neostriatum. Preliminary experiments indicated that up to 65% of specific 125I-azido-DTLET binding to rat striatal sections was still detectable following prefixation of the brain with 0.5% glutaraldehyde. These experiments also showed that up to 20-30% of the specifically bound radioactivity was covalently linked following ultraviolet irradiation and was thereby retained in tissue during subsequent postfixation and dehydration steps. Accordingly, the topographic distribution of the covalently attached azido-DTLET molecules was similar to that seen in fresh frozen sections and characteristic of that previously described for delta sites. Light and electron microscopic examination of the label in prefixed, striatal sections irradiated with ultraviolet light revealed that a significant proportion of specifically bound 125I-azido-DTLET molecules was intraneuronal. Specifically, 16% of the labelled binding sites were found in dendrites, 12% in perikarya and 4% in axon terminals. These results suggest that an important proportion of delta opioid binding sites labelled in the neostriatum correspond to receptors that are undergoing synthesis, transport and/or recycling. They also imply that a major fraction of delta sites are associated with intrastriatal neurons, as opposed to afferent axons. Approximately 44% of the labelled binding sites were associated with neuronal plasma membranes. Although most of these were found at the level of axodendritic (20%) and dendrodendritic (7%) appositions, comparison of the labelling incidence of these two compartments with their frequency of occurrence in tissue suggested that delta sites are fairly widely dispersed along neuronal plasma membranes. Only a small proportion (smaller than that of mu or kappa sites labelled in the same region) was associated with synaptic specializations. These results support the concept that delta receptors correspond to molecular entities that are distinct from mu and kappa sites and suggest that delta ligands act primarily nonjunctionally on the plasma membrane of striatal neurons.
用光亲和探针单碘叠氮 - DTLET（[D - Thr2，pN3Phe4，Leu5]脑啡肽 - Thr6）在体外选择性标记δ阿片受体，通过光镜和电镜放射自显影分析大鼠新纹状体切片中的分布情况。初步实验表明，在用0.5%戊二醛对大脑进行预固定后，大鼠纹状体切片中高达65%的特异性125I - 叠氮 - DTLET结合仍可检测到。这些实验还表明，在紫外线照射后，高达20 - 30%的特异性结合放射性以共价键连接，从而在随后的后固定和脱水步骤中保留在组织中。因此，共价连接的叠氮 - DTLET分子的拓扑分布与新鲜冷冻切片中所见相似，且具有先前描述的δ位点的特征。对用紫外线照射的预固定纹状体切片中的标记物进行光镜和电镜检查发现，相当一部分特异性结合的125I - 叠氮 - DTLET分子位于神经元内。具体而言，16%的标记结合位点位于树突中，12%位于胞体中，4%位于轴突终末。这些结果表明，新纹状体中标记的δ阿片结合位点的很大一部分对应于正在进行合成、运输和/或再循环的受体。它们还意味着，与传入轴突相反，大部分δ位点与纹状体内神经元相关。大约44%的标记结合位点与神经元质膜相关。尽管其中大部分位于轴 - 树突（20%）和树 - 树突（7%）接触水平，但将这两个区室的标记发生率与其在组织中的出现频率进行比较表明，δ位点在神经元质膜上分布相当广泛。只有一小部分（比在同一区域标记的μ或κ位点小）与突触特化相关。这些结果支持了δ受体对应于与μ和κ位点不同的分子实体的概念，并表明δ配体主要在纹状体神经元质膜上非突触地起作用。
