Figure 1. Effects of ACh on basal I_Ca,L in atrial cells plated on either glass (A and B) or laminin (C and D).

Top row: selected original I_Ca,L traces. Bottom row: consecutive measurements of peak I_Ca,L in individual experiments. Cells on glass (A and B) and laminin (C and D) were exposed to 1 μm ACh for 2 min followed by withdrawal of ACh. On glass, exposure to ACh inhibited peak I_Ca,L (b) followed, upon ACh withdrawal, by a prominent stimulation of I_Ca,L (c), which returned to baseline (d). On laminin, exposure to ACh inhibited peak I_Ca,L (b) but withdrawal of ACh failed to stimulate I_Ca,L (c). a-d indicate the times when the individual I_Ca,L traces were recorded during each experiment.