Fig. 5. Muscle denervation affects the contribution of recycled AChRs. (A) A denervated NMJ was labeled with BTX-biotin/strept-594 and imaged immediately. Three days later the synapse was re-imaged to measure the loss of fluorescence, then incubated with strept-594 to selectively label recycled AChRs. Note that 60% of the original fluorescence was lost after 3 days, whereas very little fluorescence was gained after strept-594 was added (6% of the original fluorescence), indicating that recycling of AChR is significantly decreased in denervated muscle. All three panels are displayed on the same intensity scale. (B) Bar graph summarizing the mean percentage of fluorescence intensity ±s.d. obtained from many denervated junctions. (C) An innervated synapse treated as in A, showing that a significant number of recycled AChRs return back to the postsynaptic membrane. (D) Bar graph summarizing measurements obtained from many innervated synapses.