Propofol enhances ionomycin-induced norepinephrine (NE) release (A), while it inhibits norepinephrine release triggered by high K⁺ (B). Synaptosomes from rat cortical regions were preincubated with propofol (100 μM) or control dimethyl sulfoxide and stimulated for 30 s with 5 μM ionomycin or 25 mM potassium chloride (KCl). Error bars indicate SD (n = 5 for A, n = 3 for B). Paired t test showed that a 12-min preincubation with 100 μM propofol significantly enhanced the ionomycin (5 μM)-triggered release (paired t test, t₄ = 3.21, P = 0.016), while it inhibited the depolarization (25 mM KCl)-triggered release (t₂ = 4.66, P = 0.02). *P < 0.05.