Figure 3. Fsk+IBMX-evoked responses are produced by Ca²⁺ influx.

A, sequential responses from a presynaptic cell to bath-applied Fsk+IBMX, recorded in the presence and absence of extracellular Ca²⁺. Y-axis scale bar, F₃₄₀/F₃₈₀. B, summary of the effect of removing extracellular Ca²⁺ on Fsk+IBMX-evoked responses (two-tailed t-test; P= 0.002; n= 5 cells). C, response of a presynaptic cell when perfusion was momentarily changed to buffer containing nominally 0 Ca²⁺ (grey bar) during elevation of cAMP. Y-axis scale bars in A and C are F₃₄₀/F₃₈₀.