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Electrophysiological characterization of Connexin and ZO mutants.(A–B) Synaptic responses in gjd2b/Cx34.7-/- (A) and gjd1b/Cx35.1-/- (B) mutant zebrafish show electrical and chemical components of normal amplitudes (membrane potential = −80 and −82 mv, respectively). (C) Graph summarizes the maximal amplitude (mean ± SEM) of the electrical and chemical components of the synaptic response in control conditions and in the presence of MA (200 µM), or CNQX/DAP5 (20 µM) for wt, gjd2a/Cx35.5-/-, and gjd1a/Cx34.1-/- zebrafish. Electrical: amplitude in wt averaged 6.9 ± 0.9 mV (n = 6) and it was dramatically reduced after MA application to 1.2 ± 0.3 mV (n = 6; p<0.005). Chemical: amplitude in wt averaged 1.8 ± 0.5 mV (n = 6) and averaged 5.5 ± 1.5 mV after MA (n = 6; p<0.01) and was dramatically reduced after CNQX/DAP5 application to 0.2 ± 0.03 mV (n = 6, p<0.005). CNQX/DAP5 reduced amplitude in mutants from 3.6 ± 1.0 to 0.2 ± 0.03 mV in gjd2a/Cx35.5-/- (n = 6, p<0.005) and from 3.0 ± 1.0 to 0.2 ± 0.1 mV in gjd1a/Cx34.1-/- (n = 5, p<0.05). (D) Graph summarizes the amplitude of the chemical synaptic components in control conditions and in presence of CNQX/DAP5 (20 µM) for wt and the tjp1b/ZO1b-/- mutant. CNQX/DAP5 reduced amplitude from 1.8 ± 0.5 to 0.2 ± 0.03 mV (n = 6, p<0.005) in wt and from 6.4 ± 1.5 to 0.2 ± 0.03 mV (n = 7, p<0.005) in tjp1b/ZO1b-/-. (E) Neurotransmitter release properties of chemical transmission at CEs of wt, Connexin and ZO1 mutant zebrafish. Paired-pulse ratio (mean ± SEM; see methods) of the chemical responses in wt (1.4 ± 0.2 mV, n = 8), tjp1b/ZO1b-/- (1.4 ± 0.1 mV, n = 8), tjp1a/ZO1a-/- (1.3 ± 0.1 mV, n = 4), gjd2a/Cx35.5-/- (1.5 ± 0.1 mV, n = 7), gjd1a/Cx34.1-/- (1.4 ± 0.1 mV, n = 7), gjd2b/Cx34.7-/- (1.4 ± 0.2 mV, n = 6), and gjd1b/Cx35.1-/- (1.5 ± 0.3 mV, n = 5) zebrafish. Paired-pulse ratio values were not significantly different (Kruskal-Wallis ANOVA). Associated experimental statistics can be found in Figure 3—figure supplement 1—source data 1.
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