Dose-dependent inhibition of 5-HT release in SNr by H₃R agonists R-mHA and immepip. A, B, Top, Mean profiles of [5-HT]_o versus time evoked by 20 pulses at 100 Hz (solid bar) expressed as a percentage of mean peak control. Bottom, Dose-response curves for mean peak [5-HT]_o expressed as a percentage of mean peak control for R-mHA (A) or immepip (B). A, R-mHA dose dependently inhibited [5-HT]_o (n = 14-15, Kruskal-Wallis; Dunn's t test vs control, ^**p < 0.01, ^***p < 0.001) with an IC₅₀ value of 23 nm (95% confidence interval range, 13-43 nm; R² = 0.57; Hill slope, -1.1). B, Immepip dose dependently inhibited [5-HT]_o (n = 14-19, Kruskal-Wallis; Dunn's t test vs control, ^**p < 0.01, ^***p < 0.001) with an IC₅₀ value of 43 nm (95% confidence interval range, 20-95 nm; R² = 0.65; Hill slope, -0.73; not significantly different from 1.0).