Carboxypeptidase II (CBPII) in brain metabolizes the neuroactive substance N-acetyl-L-aspartyl-L-glutamate (NAGG) to yield the elements of glutamate and N-acetyl-aspartate (NAA). In peripheral organs, CBPII is known as prostrate specific membrane antigen (PSMA), which presents an important target for nuclear medicine imaging in prostate cancer. Available PSMA ligands for PET imaging do not cross the blood–brain barrier, and there is scant knowledge of the neurobiology of CBPII, despite its implication in the regulation of glutamatergic neurotransmission. In this study we used the clinical PET tracer [¹⁸F]-PSMA-1007 ([¹⁸F]PSMA) for an autoradiographic characterization of CGPII in rat brain. Ligand binding and displacement curves indicated a single site in brain, with K_D of about 0.5 nM, and B_max ranging from 9 nM in cortex to 19 nM in white matter (corpus callosum and fimbria) and 24 nM in hypothalamus. The binding properties of [¹⁸F]PSMA in vitro should enable its use for autoradiographic investigations of CBPII expression in animal models of human neuropsychiatric conditions.

中文翻译：

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大鼠脑中 [18F]PSMA-1007 结合的放射自显影表征

脑中的羧肽酶 II (CBPII) 代谢神经活性物质 N-乙酰-L-天冬氨酰-L-谷氨酸 (NAGG)，产生谷氨酸和 N-乙酰-天冬氨酸 (NAA) 元素。在外周器官中，CBPII 被称为前列腺特异性膜抗原 (PSMA)，它是前列腺癌核医学成像的重要靶点。用于 PET 成像的可用 PSMA 配体不会穿过血脑屏障，并且尽管 CBPII 与谷氨酸能神经传递的调节有关，但对 CBPII 的神经生物学知之甚少。在本研究中，我们使用临床 PET 示踪剂 [ ¹⁸ F]-PSMA-1007 ([ ¹⁸ F]PSMA) 对大鼠脑中 CGPII 进行放射自显影表征。配体结合和位移曲线表明大脑中的单个位点，K _D约为0.5 nM，B _max范围从皮质中的9 nM到白质（胼胝体和菌毛）中的19 nM以及下丘脑中的24 nM。^{[ 18} F]PSMA 的体外结合特性应使其能够用于人类神经精神疾病动物模型中 CBPII 表达的放射自显影研究。