Sheard P W, Duxson M J
Developmental Biology Unit, University of Otago, Dunedin, New Zealand.
Brain Res Dev Brain Res. 1997 Feb 20;98(2):259-64. doi: 10.1016/s0165-3806(96)00184-8.
In a recent examination of labeled normal embryonic rat nerve terminals we have found evidence of synaptic specialisation at non-terminal regions of axons ('en passant' terminals). The specialisation typically consists of a vesicle-filled axonal swelling lying in close apposition to a zone of thickened sarcolemma, with the two structures separated by a basal lamina-filled cleft. Such 'en passant' terminals are never seen in normal mature rat muscle, where all synaptic sites form at the true termination of axonal branches. These terminals thus appear to be a transient feature of developing neuromuscular relations. Analogous structures may arise in mature muscle when axons undergo ultraterminal sprouting in response to paralysis or partial denervation. We discuss our finding in relation to the role such terminals may play in normal development and in partially denervated mature muscle.
在最近对标记的正常胚胎大鼠神经末梢的检查中，我们发现轴突非终末区域（“中途”终末）存在突触特化的证据。这种特化通常表现为一个充满囊泡的轴突肿胀，紧邻增厚的肌膜区域，这两个结构由充满基膜的裂隙分隔。在正常成熟大鼠肌肉中从未见过这种“中途”终末，在那里所有突触位点都形成于轴突分支的真正末端。因此，这些终末似乎是发育中的神经肌肉关系的一个短暂特征。当轴突因麻痹或部分去神经支配而发生超终末发芽时，成熟肌肉中可能会出现类似结构。我们结合这些终末在正常发育和部分去神经支配的成熟肌肉中可能发挥的作用来讨论我们的发现。
