Figure 7.
The number of Cav2.1 subunits and Rim1/2 proteins correlates with the active zone area. (a, b) SDS-FRL labeling of SNAP-25 in a large (a) and a small (b) active zone. (c) Correlation of the number of gold particles labeling SNAP-25 with the active zone area (n = 32 in rat#2). (d) Density of gold particles within presynaptic active zones (mean ± SD = 23.5 ± 30.3, n = 32) and in the surrounding extrasynaptic axonal plasma membranes (mean ± SD = 24.3 ± 13.4, n = 32), in comparison with the background labeling calculated on E-face plasma membranes (mean ± SD = 4.1 ± 10.6, n = 40; psynaptic < 0.01, pextrasynaptic < 0.01). (e, f) SDS-FRL labeling of the Cav2.1 subunit in a large (e) and a small (f) active zone. (g) Correlation of the number of gold particles labeling the Cav2.1 subunit with the active zone area in two rats (rat#1: black open circles, n = 34 active zones; rat#2: red open circles, n = 49 active zones). (h) Density of gold particles labeling the Cav2.1 subunit within presynaptic active zones (mean ± SD = 395.8 ± 154.8, n = 34 in rat#1) and in the surrounding extrasynaptic axonal plasma membrane (mean ± SD = 1.6 ± 2.4, n = 32 in rat#1) in comparison with the background labeling calculated on E-face plasma membranes (mean ± SD = 0.6 ± 2.3, n = 39; psynaptic < 0.01, pextrasynaptic = 0.73). (i, j) SDS-FRL labeling of Rim1/2 in a large (i) and a small (j) active zone. (k) Correlation of the number gold particles labeling Rim1/2 with the active zone area (rat#1: black open circles, n = 32 active zones; rat#2: red open circles, n = 32 active zones). (l) Density of gold particles labeling the Rim1/2 within the presynaptic active zone (mean ± SD = 374.2 ± 110, n = 32 in rat#2) and in the surrounding extrasynaptic axonal plasma membrane (mean ± SD = 6.5 ± 5.4, n = 32 in rat#2), in comparison with the background labeling calculated on E-face plasma membranes (mean ± SD = 1.7 ± 3.3, n = 40; psynaptic < 0.01, p extrasynaptic = 0.025). Scale bars: 200 nm.