Figure 1. FM1-43 labelling in muscle spindle primary afferent terminals is enhanced by stretch.

Low- (A) and high-magnification fluorescence images (B) of rat lumbrical muscle spindles labelled by exposure to 5 μm FM1-43 for 2 h at resting in situ length. C, labelling by FM1-43 is approximately 4-fold brighter if preparations are repeatedly stretched to maximal in situ length during labelling (means ± s.e.m., Student's t test). a.u., arbitrary units of grey level.