Figure 4.

Changing V_m with intracellular current injection alters [Ca²⁺]_i only during stimulation with ACh

A, simultaneous recordings of V _m (top) and F ₃₄₀/F ₃₈₀ (bottom) with −3 nA current pulses before and during 100 nm ACh. Note lack of effect of hyperpolarization on [Ca²⁺]_i until ACh is introduced. B, summary of F ₃₄₀/F ₃₈₀ values at designated values of V _m throughout levels of current injection (shown near data points) prior to ACh. Resting F ₃₄₀/F ₃₈₀ was not altered from control (arrow) while V _m ranged from −82 ± 2 mV to 4 ± 3 mV. C, summary of F ₃₄₀/F ₃₈₀ values at designated values of V _m throughout range of current injection during plateau of [Ca²⁺]_i response to ACh; one current level studied during each ACh stimulation. *P < 0.05, F ₃₄₀/F ₃₈₀ during current injection versus zero current (arrow; elevated F ₃₄₀/F ₃₈₀ versus B due to ACh). Summary data in B and C binned according to level of current injection for n = 6–7 endothelial tubes from 6–7 mice.