Effects of verapamil, dantrolene and lanthanum on catecholamine release from rat adrenal medulla.

1. The release of catecholamines (CA) from rat adrenal incubated in vivo in Locke solution was studied. 2. Acetylcholine-induced release of CA and CA release by 56 mM KCl were inhibited by verapamil and lanthanum chloride which block calcium permeability. 3. CA secretion induced by salbutamol or by theophylline was unaffected by either verapamil or lanthanum chloride. 4. Dantrolene-sodium inhibited the CA secretion induced by theophylline but only partially reduced potassium-induced release of CA. 5. Verapamil enhanced the secretion of CA induced by salbutamol (in a calcium-free medium). 6. Tyramine-induced secretion of CA was unaffected by lanthanum chloride, verapamil or dantrolene-sodium. 7. It is suggested that cyclic adenosine 3',5'-monophosphate-mediated CA secretion (induced by theophylline or salbutamol) depends on release of calcium from intracellular stores, and that CA secretion induced by tyramine is independent of intra- or extracellular calcium.