Carbon fiber Amperometry
Carbon fiber electrodes were prepared by cannulating a 10 µm-diameter
carbon fiber in polyethylene tubing (diameter: outer, 1 mm; inner, 0.5
mm). The carbon fiber tip was glued into a glass capillary for mounting
on a patch-clamp headstage, and back filled with 3 M KCl to connect to
the Ag/AgCl wire, which was kept at +700 mV. Amperometric currents were
recorded using an EPC10 USB amplifier and PatchMaster software running
on a PC computer. The sampling rate was 14.5 kHz. The sensitivity of the
electrodes was routinely monitored before and after the experiments
using 50 µM adrenaline as standard solution. Only fibers that rendered
200-300 pA of current increment after 50 µM adrenaline pulse were used
for the experiments. The bath solution was the same used in the
patch-clamp electrophysiology experiments.