Pierzga J M, Segal S S
Noll Physiological Research Center, Pennsylvania State University, University Park 16802.
Microvasc Res. 1994 Jul;48(1):50-67. doi: 10.1006/mvre.1994.1038.
Acetylcholine (ACh) dilates arterioles in skeletal muscle. Neuromuscular junctions (NMJs) are the known source of ACh in this tissue. We hypothesized that microvascular topology is related to the distribution of NMJs. To test this, the spatial relationships between NMJs, arterioles, and capillaries in the hamster cremaster muscle were investigated. Male hamsters (n = 5, 80-100 g) were anesthetized (sodium pentobarbital, 60 mg/kg) and the cremaster was perfused with fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) and Microfil compound. Excised muscles were stained for NMJs (cholinesterase reaction) and cleared in glycerin. Grid overlays divided each cremaster evenly into proximal and distal regions and 40 numbered 3 x 3-mm study fields. Five fields/region (approximately 25% of muscle area) were chosen randomly. Point counting ("counts") on a coherent test grid (component grid dimensions at x 144 magnification: 150 x 150, 300 x 300, and 450 x 450 microns) quantified NMJs, arterioles, and capillaries, respectively. NMJ:arteriole and NMJ:capillary nearest distances were obtained and arterioles nearest NMJs were classified by branch order. Filling with FITC-BSA vs Microfil indicated that all arterioles and approximately 92% of capillaries were perfused with Microfil. Relative counts (i.e., volume fractions) for capillaries were five- to sixfold greater than those for arterioles, which were two- to fivefold greater than those for NMJs. Capillary counts were similar between muscle regions and did not correlate with NMJ counts. In the distal muscle, arteriole and NMJ counts were correlated (r = 0.55, P < 0.05) and counts for both structures were greater than those in proximal regions. NMJ:capillary distances (proximal, 11.9 +/- 0.9 microns; distal, 14.5 +/- 0.6 microns) were less (P < 0.05) than respective NMJ:arteriole distances (111.1 +/- 7.1 and 89.8 +/- 3.2 microns). Fourth- and fifth-order arterioles accounted for 69% of arterioles nearest NMJs. These findings suggest that NMJs may provide a vasoactive stimulus which varies with muscle region and with location in the microvascular network.
乙酰胆碱（ACh）可使骨骼肌中的小动脉扩张。神经肌肉接头（NMJ）是该组织中已知的ACh来源。我们推测微血管拓扑结构与NMJ的分布有关。为了验证这一点，研究了仓鼠提睾肌中NMJ、小动脉和毛细血管之间的空间关系。雄性仓鼠（n = 5，80 - 100 g）麻醉（戊巴比妥钠，60 mg/kg）后，用异硫氰酸荧光素 - 牛血清白蛋白（FITC - BSA）和微显影剂灌注提睾肌。切除的肌肉用NMJ（胆碱酯酶反应）染色，并用甘油透明。网格覆盖物将每个提睾肌均匀地分为近端和远端区域以及40个编号的3×3 - mm研究区域。每个区域随机选择5个区域（约占肌肉面积的25%）。在相干测试网格（在x144放大倍数下组件网格尺寸：150×150、300×300和450×450微米）上进行点计数（“计数”），分别对NMJ、小动脉和毛细血管进行定量。获得了NMJ与小动脉以及NMJ与毛细血管的最近距离，并根据分支顺序对最靠近NMJ的小动脉进行分类。用FITC - BSA与微显影剂灌注表明，所有小动脉和约92%的毛细血管都用微显影剂灌注。毛细血管的相对计数（即体积分数）比小动脉大五到六倍，小动脉比NMJ大两到五倍。肌肉区域之间的毛细血管计数相似，且与NMJ计数无关。在远端肌肉中，小动脉和NMJ计数相关（r = 0.55，P < 0.05），且这两种结构的计数均大于近端区域。NMJ与毛细血管的距离（近端，11.9±0.9微米；远端，14.5±0.6微米）比相应的NMJ与小动脉的距离（111.1±7.1和89.8±3.2微米）小（P < 0.05）。四级和五级小动脉占最靠近NMJ的小动脉的69%。这些发现表明，NMJ可能提供一种血管活性刺激，该刺激随肌肉区域和微血管网络中的位置而变化。
