Cylindrical carbon-fiber microelectrodes (50–100 μm of exposed fiber) were prepared as described previously (Cahill et al., 1996) with T650 fibers (6 μm diameter, Amoco Corporation, Greenville, SC) inserted into a glass pipette (A-M Systems, Carlsborg, WA). The carbon-fiber electrode was held at − 0.4 V versus Ag/AgCl, and periodically a cyclic voltammogram was acquired (100 ms intervals for chemical measurements and 200 ms for combined recordings). The applied potential was scanned to + 1.3 V and back in a triangular fashion at 400 V/s in 8.5 ms (Heien et al., 2003). Stimulation timing, voltage application, and data collection was achieved with an interface board (National Instruments, Austin, Texas) in a Pentium IV computer running custom-designed LABVIEW (National Instruments) software.
