Figure 4.

Electrical coupling of neighboring Xenopus embryonic cells at morula stage (A,B), monitored by measuring the coupling ratio (V₂/V₁). In the absence of the CaM-inhibitor trifluoperazine (TFP), 100% CO₂ reduces V₂/V₁ to nearly zero, while, with 5 µM TFP, CO₂ has a minimal effect (A). The effect of TFP is slowly reversible (A). The most specific CaM-blocker, calmidazolium (CDZ), also inhibits the effect of CO₂ (B). With 100 nM [CDZ], 100% CO₂ causes V₂/V₁ to only drop to 0.5–0.7 (B). Another CaM inhibitor (W7, 100 µM) also effectively inhibits Ac-induced Rj rise in crayfish axons (C), while its control (W5) is totally ineffective (C). A, B and C, from References [76,93,94], respectively.