Fig. 9. Time course to conduction failure during 100-μm ketamine perfusion. A representative selection of action potential traces are displayed for the times indicated following the beginning of exposure to 100 μm ketamine at physiologic temperatures (35–36°C, A ). This is the same neuron as presented in fig. 7A. Each frame displays responses to three consecutive vagal shocks at 1 Hz. Average conduction velocity (normalized, B ) of C-type afferent fiber (1.4 m/s, control). Data are averages of four C-type neurons except for points at 10, 11, and 12 min, where n = 3. Note that as perfusion time increased, the response variance increased (SDs) as fewer shocks were able to elicit somatic action potentials and conduction velocity dropped to zero.