Nicotine-stimulated norepinephrine (NE) release. Rat hippocampal synaptosomes were loaded with [³H]norepinephrine and perfused with buffer with or without antagonist for 20 min before sample collection. Nicotine-stimulated release is defined as 100%, and the corresponding basal release at t = 9 min is defined as zero. Data are plotted as described in Figure 1. A, Unstimulated release of [³H]norepinephrine. B, [³H]norepinephrine release after a 1 min pulse of 100 μm nicotine (horizontal bar in this and all subsequent panels). C, Nicotine-stimulated release in the presence of the nicotinic antagonist mecamylamine.D, Nicotine-stimulated release in the absence of Ca²⁺. E, α-Conotoxin MII (100 nm) blocks ∼10% of nicotine-evoked release of [³H]norepinephrine.