AIMS Impairment of blood-brain barrier (BBB) is involved in numerous neurological diseases from developmental to aging stages. Reliable imaging of increased BBB permeability is therefore crucial for basic research and preclinical studies. Today, the analysis of extravasation of exogenous dyes is the principal method to study BBB leakage. However, these procedures are challenging to apply in pups and embryos and may appear difficult to interpret. Here we introduce a novel approach based on agonist-induced internalization of a neuronal G protein-coupled receptor widely distributed in the mammalian brain, the somatostatin receptor type 2 (SST2). METHODS The clinically approved SST2 agonist octreotide (1 kDa), when injected intraperitoneally does not cross an intact BBB. At sites of BBB permeability, however, OCT extravasates and induces SST2 internalization from the neuronal membrane into perinuclear compartments. This allows an unambiguous localization of increased BBB permeability by classical immunohistochemical procedures using specific antibodies against the receptor. RESULTS We first validated our approach in sensory circumventricular organs which display permissive vascular permeability. Through SST2 internalization, we next monitored BBB opening induced by magnetic resonance imaging-guided focused ultrasound in murine cerebral cortex. Finally, we proved that after intraperitoneal agonist injection in pregnant mice, SST2 receptor internalization permits analysis of BBB integrity in embryos during brain development. CONCLUSIONS This approach provides an alternative and simple manner to assess BBB dysfunction and development in different physiological and pathological conditions.

中文翻译：

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一种使用 GPCR 内化检测血脑屏障通透性的简单新方法

AIMS 血脑屏障 (BBB) 受损涉及从发育阶段到衰老阶段的许多神经系统疾病。因此，血脑屏障通透性增加的可靠成像对于基础研究和临床前研究至关重要。今天，外源性染料外渗的分析是研究 BBB 渗漏的主要方法。然而，这些程序在幼崽和胚胎中应用具有挑战性，并且可能看起来难以解释。在这里，我们介绍了一种基于激动剂诱导的神经元 G 蛋白偶联受体内化的新方法，该受体广泛分布于哺乳动物大脑中，生长抑素受体 2 型 (SST2)。方法 经临床批准的 SST2 激动剂奥曲肽 (1 kDa)，腹腔注射时不会穿过完整的 BBB。然而，在 BBB 渗透性部位，OCT 外渗并诱导 SST2 从神经元膜内化到核周区室。这允许通过使用针对受体的特异性抗体的经典免疫组织化学程序明确定位增加的 BBB 通透性。结果我们首先在显示允许血管通透性的感觉室周器官中验证了我们的方法。通过 SST2 内化，我们接下来监测了由磁共振成像引导的聚焦超声在小鼠大脑皮层中诱导的 BBB 开放。最后，我们证明在怀孕小鼠腹膜内注射激动剂后，SST2 受体内化允许分析大脑发育过程中胚胎中 BBB 的完整性。