The blood-nerve barrier does not extend beyond the motor axon.

<p>A–C) Live NMJ from a F3 larva reared at 30°C. The glial membrane processes were labeled using repo>CD8-GFP (green) and the SSR labeled using ShCter-DsRed (blue). A 10 kDa fluorescent dextran (red) was used to test for the presence of a permeability barrier. Glial area = 13.77 µm². Scale bar, 15 µm. A) A single Z-slice from a focal plane at the surface of the NMJ showed dextran permeation into the synaptic ^region. The motor nerve projection is marked (asterisk) between muscles 6 and 7, and showed dye exclusion from the motor axons. B) The boxed region in panel A was digitally scaled by 200%. The fluorescent dextran pooled around the SSR even with the close association of the glial processes (arrows). C) The boxed region in A was digitally scaled by 200%. Fluorescent dextran was excluded along the axon (between the arrows) where the GFP tagged glial membrane was present and demarks the regions where the blood-nerve barrier is found.