Figure 6.

Uniformity of Ca²⁺ channel-dependent Ca²⁺ accumulation in motor terminal branches. A. Presynaptic Ca²⁺ accumulation was monitored with a Ca²⁺-sensitive green fluorescent protein, GCaMP, expressed in motoneurons (see Methods). Fluorescence intensities in WT presynaptic boutons before and during nerve stimulation (20 Hz, 5 s) are shown. B. Ca²⁺ accumulation along motor terminals in WT and rut. Note uniform amplitudes of ΔF/F within individual nerve terminals. C. Increased sensitivity of rut¹ terminals to a Ca²⁺ channel blocker, Co²⁺. Peak ΔF/F during 20-Hz stimulation was significantly reduced by 30 µM Co²⁺ in rut but not in WT terminals (***, p < 0.001; t-test). D. Increased variation among rut terminals after partial Co²⁺ blockade (30 µM). The symbols in B and D represent the relative positions of individual boutons along the type Is terminal. Boutons along individual WT (filled circles) and rut (open squares) terminals are connected with line segments.