Figure 5

Ultrastructural events indicate that nerve terminal loss progresses by retraction. Nerve and muscle preparations were fixed for immuno-electron microscopy and labelled for P2X7 receptor subunits (dark DAB reaction product) to facilitate localisation. When preparations were fixed and immunostained subsequent to a 30 min BzATP (100 μM) pulse frequent abnormal appearances were found. These included; widened synaptic clefts with the appearance of mega-omega profiles (asterisk) (a), fine processes of terminal Schwann cells invaded the synaptic cleft (b: arrowhead), boutons which were detached from the muscle endplate and where terminal Schwann cell processes had come to intervene between the two (c: arrow). In control nerve muscle preparations incubated in physiological saline for 30 min prior to fixation and immunostaining (d), motor nerve terminal boutons contained reaction product for P2X7RS, intact mitochondria (Mi), densely packed synaptic vesicles (SV), were closely apposed to muscle endplates (EP) and overlain by terminal Schwann cell (tSc). a, b, d = 500 nM, c = 1 μM