Protein kinase A modulates 3H-GABA release in cultured human airway epithelial (BEAS-2B) cells. Terbutaline (100 μM), a β-adrenergic agonist, and forskolin (10 μM), an activator of adenylyl cyclase, both decrease depolarization-induced fractional 3H-GABA release in cultured human airway epithelial cells. n = 6–8, ***p < 0.001, **p < 0.01, *p < 0.05