Figure 2.

Figure 2. Electrical and chemical transmitting areas are mutually exclusive.

(A, B) Expanded synaptic contact areas labeled with anti-Cx35.5 (green) and anti-GluR2 (magenta) (A: projection of 18 sections at 0.55 µm z-step size; B: projection of 15 sections at 0.50 µm z-step size). (C) ‘En face’ view of an expanded synaptic contact area showing that GluR2 labeling is restricted to the periphery of the contact, whereas Cx35.5 labeling is distributed throughout the whole contact area (projection of 46 sections at 0.65 µm z-step size). (D) Graph shows the lack of colocalization (see ‘Materials and methods’) between Cx35.5 and GluR2 fluorescence at individual club ending (CE) contacts, determined by the Manders’ colocalization coefficient: GluR2/Cx35.5 0.10 ± 0.020 (x-axis); Cx35.5/GluR2 0.08 ± 0.015 (y-axis), n = 13 CEs from five fish. Cross mark indicates the average value. (E) Quantification of fluorescence over area for Cx35.5 and GluR2 at the ‘Center” (central ¾) and ‘Periphery’ (remaining ¼) of the CE contact area. Values of fluorescence/area are represented as normalized to those of Cx35.5 in the center (higher value): GluR2 center: 0.25 ± 0.069; Cx35.5 periphery: 0.70 ± 0.126; GluR2 periphery: 0.96 ± 0.039 (n = 5 CEs from five fish). While fluorescence for Cx35.5 and GluR2 is not significantly different in the periphery (n.s.), Cx35.5 distinctly predominates over GluR2 at the center (Student’s t-test, p<0.0001). (F) Graphical description of the center vs. periphery distribution of Cx35.5 and GluR2 for the data described in (E). The scale bars represent actual dimensions; expanded images were not adjusted for expansion factor.