Fig. 2

Decreased extracellular serotonin marks chronic stress. A, C Example color plots from control and CMS mice, respectively. B, D Example cyclic voltammograms from control and CMS mice, respectively. E Evoked hippocampal serotonin concentration with time in control (blue; n = 10) and CMS (gray; n = 16) mice. F Example basal serotonin color plot. G Example basal serotonin cyclic voltammogram from which basal serotonin was calculated inset equation (τ = Surface Concentration, Q = Charge, n = Charge on the Molecule, F = Faraday Constant, and A = Surface Area). H Average basal serotonin in control (blue; n = 7) and CMS (gray; n = 13) mice are shown as bars and individual animals are denoted by circles. Error is shown as SEM and an asterisk denotes significance via t test (p < 0.05). I k-means clustering using extracellular serotonin to predict chronic stress (k = 2). Mice are clustered, based on basal hippocampal serotonin levels, into depressed and control. 80% data is used for training and 20% data is used for testing. J Serotonin concentration and sucrose preference at 1 h (n = 16), time spent in the closed arms of the EZM (n = 17), immobility in the FST (n = 4), and active time in the TST (n = 17). R = Pearson’s Correlation Coefficient