Fig. 8.
Presynaptic low-threshold Ca currents, presynaptic changes in Ca fluorescence, and associated IPSPs are correlated in heart interneurons. A, Simultaneous recordings of presynaptic low-threshold Ca currents (ICa) in voltage clamp and changes in Ca fluorescence (ΔF, at the site indicated on theinset) and IPSPs in a pair of oscillator interneurons. The preparation was bathed in 0 mm Na+/5 mm Ca2+ saline and an increasing series of depolarizing voltage pulses (from a holding potential of −70 mV) was imposed on the presynaptic cell. Changes in Ca fluorescence (ΔF) recorded at 30 Hz. B, The experiment of panelA was repeated in five preparations, and the relations of average integrated ICa, ΔF, and IPSP to the command potential during the pulse were plotted as mean ± SE. C, Using the data shown in panelB the relations between average integrated IPSP and average integrated ΔF and ICa were plotted, and the relation between average integrated ΔF andICa was plotted. Solid straight lines are from linear regression of the data, and dotted lines are 95% confidence intervals of the regression line.