Fig. 4. Summary ketamine dose–response relations for cardiac parasympathetic neurons and the role of α7subunit–containing nicotinic receptors (n = 10). Ketamine, at increasing concentrations, continued to inhibit the nicotine-evoked inward current (normalized to control, A ) in the presence of α bungarotoxin (αBgTx), and this inhibition was statistically significant at a ketamine concentration of 10 μm. However, in the presence of αBgTx, nicotine did not evoke an increase in miniature glutamatergic synaptic event (mini) frequency (B ), and ketamine at all concentrations examined (0.1–10 μm) had no further effect on mini frequency. Ketamine, at all concentrations examined (0.1–10 μm), had no significant effect on mini amplitude (C ) in the presence of αBgTx.