Carbon fiber

CFMEs were fabricated as previously described. Briefly, a vacuum pump was used to aspirate 7 μm diameter carbon fibers (Goodfellow Cambridge LTD, Huntingdon, UK) into glass capillaries (1.2 mm D.D. and 0.68 mm I.D., 4 in long; A-M Systems, Inc., Carlsborg, WA) which were then pulled using a PE-22 heated coil puller (Narishige Int. USA, East Meadow, NY) to form two electrodes. Exposed carbon fibers were trimmed to a length of 50–100 μm. To seal the CFMEs, the tips were dipped in epoxy resin (EPON resin 815C and EPIKURE 3234 curing agent, Miller-Stephenson, Danbury, CT) for 45 seconds and cured at 100°C for 1 h. CFMEs were treatment via an isopropanol soak for at least 20 min prior to initial use.
All CFMEs were pre-calibrated against standard solutions of 5-HT, introduced to a flow cell through a six-port valve (Valco Instruments Company Incorporated, Houston, TX, USA). The flow solution, which consisted of mouse aCSF without D-glucose, was pumped at a rate of 2 mL min⁻¹ using a syringe pump (Chemyx Inc, Stafford, TX, USA). Injections were conducted in triplicate to determine the 5-HT concentration per nanoamp of current for each CFME.

Carbon fibers (.007 mm, Goodfellow, Huntingdon, England) were aspirated into cylindrical glass capillaries (1.2 mm by 0.68 mm, A-M Systems, Inc., Carlsborg, WA) using a vacuum pump (DOA-P704-AA, GAST, Benton Harbor, MI) to form carbon-fiber microelectrodes. The capillary was pulled to form two electrodes on a vertical pipette puller (Narishige, model PC-100 and PE-22, Tokyo, Japan), and the fiber cut to lengths of approximately 100–150 microns. Glass insulated electrodes were epoxied with Epon 828 epoxy (Miller-Stephenson, Morton Grove, IL) and diethylenetriamine (Sigma Aldrich, Milwaukee, WI). Protruding carbon-fiber microelectrode tips were dipped in the epoxy hardener mixture (0.8% by mass resin) for approximately 15 seconds and then rinsed in acetone to wash away any excess residual acetone.⁵⁶ The electrodes were cured in the oven for 3 h at 165°C.

CFMs were fabricated employing 7 μm diameter carbon-fibers (Goodfellow Corporation, Coraopolis, PA, USA) aspirated into glass capillaries (0.6 mm external diameter, 0.4 mm internal diameter; AM Systems, Inc., Sequim, WA, USA). A carbon-glass seal was formed using a vertical micropipette puller (Narishige Group, Tokyo, Japan). The exposed length of the carbon fiber was trimmed to 150 μm under an optical microscope. Microelectrodes were electro-plated with Nafion as described previously (Hashemi et al. 2009 (link)).

CFMs were fabricated with 7 μm diameter carbon-fibers (Good-fellow Corporation, PA, USA) aspirated into glass capillaries (0.6 mm external diameter, 0.4 mm internal diameter, A-M systems, Inc., Sequim, WA). A carbon-glass seal was formed via a vertical micropipette puller (Narishige Group, Tokyo, Japan). The exposed length of the carbon fiber was trimmed to 150 μm under an optical microscope. Microelectrodes were electro-plated with Nafion as described previously.^{4 (link)}

Carbon fiber microelectrodes were manufactured by aspirating 7 μm diameter carbon-fibers (Goodfellow Inc, Coraopolis, PA) into glass capillaries (0.6 mm external diameter, 0.4 mm internal diameter, A-M Systems Inc., Sequim, WA). Fibers were sealed into the capillaries with a vertical pipette puller (Narishige Group, Tokyo, Japan). The exposed fiber was trimmed to approximately 50 μm for evaluation of dopamine and precisely 150 μm under a low-light power microscope for evaluation of serotonin, as this length is critical for proper measurement of serotonin (Hashemi et al. 2009 (link); Denton et al., 2019 (link)). Nafion, a cation exchange polymer, was electrodeposited onto the carbon fiber portion of each serotonin electrode and dried for 10 minutes at 70º C (Hashemi et al. 2009 (link); Denton et al., 2019 (link)).

CFMs were fabricated in house using ~7 μm diameter carbon fibers (Goodfellow Corporation, PA, USA). The carbon fibers were aspirated into glass capillaries (ED 0.6 mm, ID 0.4 mm; A-M systems, Inc., Sequim, WA, USA) and pulled via a vertical micropipette puller (Narishige Group, Tokyo, Japan). Under an optical microscope, carbon fibers were cut to 150 μm. An electrical connection was forged between the carbon fiber and connection wire using silver paint. CFMs were then electroplated with nafion (Hashemi et al., 2009 (link)).