Figure 3.
Effect of intravenous administration of cumulative doses of WIN on DR 5-HT neurons. A–D, Integrated firing rate histograms of 5-HT neurons illustrating that low doses of WIN (0.1–0.2 mg/kg, i.v.) rapidly increased single-unit firing activity. A, This effect was reversed by RIM (1.0 mg/kg, i.v.; n = 4) but not by CPZ (0.02 mg/kg, i.v.; n = 4). B–D, High dose of WIN (0.30–0.50 mg/kg, i.v.) rapidly decreased single-unit firing activity. This effect was reversed by CPZ (0.02 mg/kg, i.v.) in two of three neurons (D) and partially reversed (B) or unreversed (C) by RIM (1 mg/kg, i.v.) in one and three neurons, respectively. 5-HT neuronal firing rate in each histogram is plotted as spikes per 10 s. Calibration bar on right side of each histogram, 1 min. The vertical lines depicted below each histogram represent the frequency of neuronal burst activity such that each tick corresponds to a burst discharge event. E, WIN (0.05–0.5 mg/kg, i.v.) produced a biphasic response profile in 5-HT single-unit activity. F, Line graphs showing that cumulative doses of WIN modulated 5-HT neuronal burst activity measured as percentage of spikes within bursts (top) and mean burst length (bottom). *p < 0.05 or **p < 0.01 vs baseline (vehicle).
