Nässel D R, Holmqvist B I, Movérus B J
Department of Zoology, University of Lund, Sweden.
J Comp Neurol. 1989 May 15;283(3):450-63. doi: 10.1002/cne.902830312.
In the neural sheath of the fused thoracicoabdominal ganglia of the blowfly Calliphora erythrocephala, extensive neurohaemal areas can be seen in the electron microscope. A separate set of neurohaemal areas located in the sheath of the lateral abdominal nerve roots contain neural terminals of at least three morphological types. To determine which bioactive substances are stored and possibly released from the neurons supplying these neurohaemal areas, we applied a large number of antisera raised against different neuropeptides of invertebrate and mammalian type. Antisera to two types of neuropeptides react with neurons innervating the sheath of the abdominal nerve roots: antisera to lysine-vasopressin and proctolin. There are only 14-24 vasopressin-like immunoreactive (VPLI) neurons in the entire nervous system of Calliphora. These are all restricted to a bilateral cluster in the fused abdominal ganglia. From this cluster, the neurohaemal areas in abdominal nerve roots are supplied. Proctolin-like immunoreactivity (PLI) can be seen in a large number of neurons in the nervous system of blowflies. The supply of PLI terminals to the abdominal nerve roots is from 12 to 14 neurons in a bilateral cluster of abdominal PLI neurons. It is clear from light- and electron-microscopic immunocytochemistry that the two antisera label two separate populations of neurons that form overlapping terminals in the neural sheath. The immunoreactive terminals are located just below the permeable acellular basal lamina of the neural sheath. Hence, it is likely that at least two different bioactive peptides can be released neurohormonally into the circulation. An additional set of four efferent PLI neurons send axons into the medial abdominal nerve. These do not form neurohaemal terminals in the nerve root, but may innervate the hindgut. Also in the larval nervous system, VPLI and PLI neurons can be recognized. In the larva, the peptide-containing neurons are segmentally arranged. The 14 larval VPLI neurons supply segmental abdominal nerves with axons that run inside the nerves to their targets. During metamorphosis, the segmental nerves fuse and the VPLI axons invade the neural sheath where they arborize and form varicose terminals. About the same number of PLI neurons could be detected in the abdominal ganglia of larval and adult flies. Only for a set of four caudal PLI neurons could efferent axons be traced in the larva. These axons run inside the medial abdominal nerves. The same four PLI neurons, with the same axonal projections, can be recognized in the adults.
在红头丽蝇胸腹融合神经节的神经鞘中，电子显微镜下可观察到广泛的神经血器官区域。位于腹侧神经根鞘内的另一组神经血器官区域包含至少三种形态类型的神经终末。为了确定哪些生物活性物质储存在为这些神经血器官区域提供神经支配的神经元中并可能从中释放，我们应用了大量针对无脊椎动物和哺乳动物类型不同神经肽产生的抗血清。两种神经肽的抗血清与支配腹神经根鞘的神经元发生反应：赖氨酸加压素抗血清和促肠肌肽抗血清。在红头丽蝇的整个神经系统中，仅有14 - 24个加压素样免疫反应性（VPLI）神经元。它们全部局限于融合腹神经节中的一个双侧细胞簇。从这个细胞簇发出神经支配腹神经根中的神经血器官区域。在丽蝇的神经系统中，大量神经元可见促肠肌肽样免疫反应性（PLI）。为腹神经根提供PLI终末的是腹侧PLI神经元双侧细胞簇中的12至14个神经元。光镜和电镜免疫细胞化学结果清楚表明，这两种抗血清标记了两个不同的神经元群体，它们在神经鞘中形成重叠的终末。免疫反应性终末位于神经鞘可渗透的无细胞基膜下方。因此，很可能至少有两种不同的生物活性肽可通过神经激素方式释放到循环中。另外一组四个传出PLI神经元将轴突发送到腹内侧神经。它们不在神经根中形成神经血器官终末，但可能支配后肠。在幼虫神经系统中也可识别出VPLI和PLI神经元。在幼虫中，含肽神经元呈节段性排列。14个幼虫VPLI神经元为节段性腹神经提供轴突，这些轴突在神经内运行至其靶标。在变态过程中，节段性神经融合，VPLI轴突侵入神经鞘，在那里分支并形成曲张终末。在幼虫和成虫的腹神经节中可检测到数量大致相同的PLI神经元。在幼虫中，仅能追踪到一组四个尾侧PLI神经元的传出轴突。这些轴突在腹内侧神经内运行。在成虫中可识别出相同的四个PLI神经元，具有相同的轴突投射。
