Electrophysiological studies with connexin-mimetic peptides. (A) Whole-cell patch-clamp recordings and histogram confirming that 600 μM 37,40Gap 26 and 100 μM 43Gap 26 did not depress endothelial hyperpolarizations evoked by 30 μM CPA. (B and C) Original recordings and histograms comparing the effects of the peptides and 2,000 units/ml catalase on subintimal (B) and subadventitial (C) hyperpolarizations evoked by CPA. 37,40Gap 26 attenuated the transmission of endothelial hyperpolarization to subintimal smooth muscle, whereas 43Gap 26 selectively impaired transmission of subintimal hyperpolarization across the vessel wall. The effects of both peptides were prevented by 100 μM 5-MTHF and (6R)-BH4 but not by 100 μM FA or BH2. Catalase prevented the effects of 37,40Gap 26 on subintimal hyperpolarization, but not those of 43Gap 26 on subadventitial hyperpolarization. *, P < 0.05, compared with control.