The effect of chronic lithium (0.1% in the diet for 28 days), amitriptyline (10 mg/kg SC daily for 14 days), and electroconvulsive shock (ECS) (given 5 x under halothane anaesthesia on alternate days) on the binding of the L-type calcium channel antagonist (+)-(3H)-PN 200-110 to rat cortical and hippocampal homogenates and the binding of the N-type calcium channel antagonist (125I)-omega-conotoxin to rat cortical homogenates was measured. These treatments did not alter the number or affinity of the binding sites for either ligand, suggesting that it is unlikely that the actions of chronic lithium, amitriptyline, and ECS affect calcium channel binding.