Morris J F, Pow D V
Department of Human Anatomy, Oxford University, United Kingdom.
Anat Rec. 1991 Dec;231(4):437-45. doi: 10.1002/ar.1092310406.
Tannic acid methods have been applied to capture the exocytosis of peptide-containing granules from peptidergic neurons. The captured exocytoses have been quantitated to assess the proportion and amount of peptide released at different parts of the neuronal membrane. Examination of hypothalamic synaptic boutons shows that only about one-half of the peptidergic vesicles is exocytosed into the synaptic cleft and also that exocytosis also occurs from undilated peptidergic axons. Study of the magnocellular neurosecretory system reveals that all parts of their extensive terminal arborization appear to be equally capable to exocytose peptide. Only about one-half of their peptide is released from their nerve endings, which about the capillaries. The remainder is released much deeper in the lobules of secretory tissue where its principal target(s) could be the pituicytes and/or neurosecretory axons. Dendrites of magnocellular neurons are also capable of releasing peptide by exocytosis and dendrites could release sufficient oxytocin and vasopressin to account for the peptide known to be released into the hypothalamus. We conclude that peptidergic neurons release substantial amounts of peptides from all of their processes and that this must be taken into account when considering what functions those peptides might serve.
单宁酸法已被用于捕捉肽能神经元中含肽颗粒的胞吐作用。对捕获的胞吐作用进行定量，以评估在神经元膜不同部位释放的肽的比例和数量。对下丘脑突触小体的检查表明，只有大约一半的肽能小泡会胞吐到突触间隙中，而且未扩张的肽能轴突也会发生胞吐作用。对大细胞神经分泌系统的研究表明，其广泛终末分支的所有部分似乎都同样有能力进行肽的胞吐作用。它们只有大约一半的肽从神经末梢释放，这些神经末梢靠近毛细血管。其余的则在分泌组织小叶的更深部位释放，其主要靶标可能是垂体细胞和/或神经分泌轴突。大细胞神经元的树突也能够通过胞吐作用释放肽，并且树突可以释放足够的催产素和血管升压素，以解释已知释放到下丘脑中的肽。我们得出结论，肽能神经元从其所有突起中释放大量肽，在考虑这些肽可能发挥的功能时，必须考虑到这一点。
