PC-12 Culture. PC-12 cells (CRL-1721.1, ATCC, Manassas, VA, USA) were cultured in RPMI-1640 media (A10491, Gibco, Jenks, OK, USA) containing 10% horse serum, 5% fetal bovine serum (FBS) and 5% penicillin streptomycin (30-002-Cl, Corning, Corning, NY, USA). Media was changed every 2-3 days and cells were passaged at ~80% confluency by dissociating with trypsin. Cells were maintained on standard treated tissue culture dishes in a 37ºC humidified incubator with 5% CO2 until FSCV measurements were ready to be performed. Pinealocyte Culture. Experiments involving harvest of rat pineal glands were approved by and conducted in accordance with the UVM Institutional Animal Care and Committee. Pineal glands were dissected from male Sprague Dawley rats, pooled and immediately placed in Hibernate-E (Life Technologies, cat #: A12476-01) on ice until all glands were collected. Glands were then washed in Hibernate-E and gently resuspended in dissociation media containing Hibernate-E mixed with papain (20U/mL -Worthington Biochemicals, cat #: LK003178) and DNAse I (.1mg/mL -Sigma, cat #: DN25). This suspension was incubated for 30 min at 37ºC at which time pinealocyte culture media (DMEM Gibco 11960-044, 10% FBS, 1x GlutaMAX, 1xPen/Strep) was added in equal volume to the dissocation media. Cells were then plated in poly-d-lysine coated 12-well plate at 75,000 cells/well with pinealocyte culture media. Cells were maintained for ~2 weeks in a 37ºC humidified incubator with 5% CO2 until FSCV measurements were ready to be performed.