Pierce J P, Kurucz O S, Milner T A
Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, New York 10021, USA.
Hippocampus. 1999;9(3):255-76. doi: 10.1002/(SICI)1098-1063(1999)9:3<255::AID-HIPO6>3.0.CO;2-S.
While the morphometry of classical transmitter systems has been extensively studied, relatively little quantitative information is available on the subcellular distribution of peptidergic dense core vesicles (DCVs) within axonal arbors and terminals, and how distribution patterns change in response to neural activity. This study used correlated quantitative light and electron microscopic immunohistochemistry to examine dynorphin B-like immunoreactivity (dyn B-LI) in the rat hippocampal mossy fiber pathway before and after seizures. Forty-eight hours after seizures induced by two pentylenetetrazol injections, light microscopic dyn B-LI was decreased dorsally and increased ventrally. Ultrastructural examination indicated that, in the hilus of the dentate gyrus, these alterations resulted from changes that were almost entirely restricted to the profiles of the large mossy-like terminals formed by mossy fiber collaterals (which primarily contact spines), compared to the profiles of the smaller, less-convoluted terminals found on the same collaterals (which primarily contact aspiny dendritic shafts). Dorsally, mossy terminal profile labeled DCV (/DCV) density dropped substantially, while ventrally, both mossy terminal profile perimeter and /DCV density increased. In all terminal profile examined, /DCVs also were closely associated with the plasma membrane. Following seizures, there was a reorientation of /DCVs along the inner surface of mossy terminal profile membranes, in relation to the types of profiles adjacent to the membrane: in both the dorsal and ventral hilus, significantly fewer /DCVs were observed at sites apposed to dendrites, and significantly more were observed at sites apposed to spines. Thus, after seizures, changes specific to: (1) the dorsoventral level of the hippocampal formation, (2) the type of terminal, and (3) the type of profile in apposition to the portion of the terminal membrane examined were all observed. An explanation of these complex, interdependent alterations will probably require evoking multiple interrelated mechanisms, including selective prodynorphin synthesis, transport, and release.
虽然经典递质系统的形态计量学已得到广泛研究，但关于肽能致密核心囊泡（DCV）在轴突分支和终末内的亚细胞分布以及其分布模式如何响应神经活动而变化的定量信息相对较少。本研究采用相关的定量光镜和电镜免疫组织化学方法，检查癫痫发作前后大鼠海马苔藓纤维通路中强啡肽B样免疫反应性（dyn B-LI）。两次注射戊四氮诱发癫痫发作48小时后，光镜下dyn B-LI在背侧降低而在腹侧增加。超微结构检查表明，在齿状回门区，这些改变几乎完全源于苔藓纤维侧支形成的大型苔藓样终末（主要接触棘突）的轮廓变化，与同一侧支上较小、较少卷曲的终末（主要接触无棘树突干）的轮廓相比。在背侧，苔藓终末轮廓标记的DCV（/DCV）密度大幅下降，而在腹侧，苔藓终末轮廓周长和/DCV密度均增加。在所有检查的终末轮廓中，/DCV也与质膜紧密相关。癫痫发作后，/DCV沿着苔藓终末轮廓膜的内表面重新定向，与邻近膜的轮廓类型有关：在背侧和腹侧门区，与树突相对的部位观察到的/DCV明显减少，而与棘突相对的部位观察到的明显增多。因此，癫痫发作后，观察到了特定于：（1）海马结构的背腹水平，（2）终末类型，以及（3）与所检查的终末膜部分相对的轮廓类型的变化。对这些复杂、相互依存的改变的解释可能需要唤起多种相互关联的机制，包括前强啡肽的选择性合成、运输和释放。
