The use of synaptic basal lamina and its components to identify sites of recent morphological alterations at mammalian neuromuscular junctions

While muscle fibers are ensheathed in basement membrane material, the extracellular matrix at their synaptic segment, the neuromuscular junction (NMJ), is specialized and contains factors that are essential for the proper development, maintenance, and regeneration of the synapse after injury. Immunohistochemical studies have been critical in characterizing the composition of the synaptic basal lamina at the NMJ. Although NMJs are extremely stable synapses, they can undergo structural alteration both pre- and postsynaptically, especially during development and in response to injury. Even though there are no permanent molecular markers currently known for synaptic sites that have undergone elimination or remodeling, the relatively stable and specialized nature of the synaptic basal laminar components-which aided in their initial identification and characterization-makes them excellent markers for identification of recently eliminated synaptic sites and as ultrastructural indicators of morphological alterations of cellular synaptic components.