Figure 1.

Morphology and neurotransmission at WT and α_1A −/− NMJs. Filled symbols, WT; open symbols, −/−. (A) NMJs from WT (Left) and α_1A −/− (Right) mice stained with FM1–43 (Upper) and α-bungarotoxin (Lower) as pre- and postsynaptic markers. [Scale bars: 10 μm (Upper Left) and 5 μm (all others).] (B) Cumulative distributions of postsynaptic site areas are smaller in the −/− (P < 0.001). (C) Double-logarithmic plot of quantal content vs. [Ca²⁺]_o/[Mg²⁺]_o. At low [Ca²⁺]/[Mg²⁺] ratios, data were fitted with a linear equation where the slope of the plot was 2.7 for both WT and −/− NMJs (continuous lines) (r² > 0.9). Quantal content values at high [Ca²⁺]/[Mg²⁺] were significantly different (**, P < 0.001). (D) MEPP amplitude distribution histograms. (E) Averaged traces of EPPs evoked by a 17-ms paired pulse stimulation (Upper, WT; Lower, −/−). (F) Paired pulse index (*, P < 0.05; **, P < 0.001).