Fig. 3: Chronic voluntary alcohol consumption retricts dynamic range of accumbal dopamine release.

A An input-output curve showing the peak dopamine release (nA) evoked by single pulse stimulations across ascending intensities (50–900 µA). Curves were fit with a 4-parameter sigmoidal regression, and best-fit values are shown with 95% confidence band and half-maximal excitatory amperage (EA₅₀) indicated (controls: EA₅₀ = 316.4 µA; drinkers: EA₅₀ = 315.9 µA). B–D Comparison of best-fit values between drinkers and controls. B Subjects with ethanol history have an attenuated upper asymptote compared to controls, indicative of decreased maximal dopamine release magnitude (unpaired t-test; t₂₆ = 2.710, p = 0.0118). C There is no difference between groups at the bottom of the curve plateau (unpaired t-test; t₂₆ = 1.033, p = 0.3110). D Drinkers show a decreased span of the input-output curve [upper plateau minus lower plateau] compared to control subjects suggesting a lower dynamic range of dopamine release (unpaired t-test; t₂₆ = 2.365, p = 0.0258). E There was no difference in the EA₅₀ between drinkers and controls (unpaired t-test; t₂₆ = 0.01, p = 0.99). (controls: n = 3; drinkers: n = 7) All statistical tests were two-tailed and values indicate mean ± SEM. (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001).