Transient K+ current is blocked by lanthanum in Drosophila neurons.

The potassium A-current (IK(A)) is important in regulating the membrane potential between action potentials. The whole-cell patch-clamp technique was applied to cultured Drosophila neurons derived from embryonic neuroblasts. IK(A) was measured from neurons before and after application of 0.1 mM lanthanum to the external saline. IK(A) was smaller in the lanthanum-containing saline (7+/-1 pA) than in the control saline (34+/-6 pA). Activation and inactivation of IK(A) were unchanged by lanthanum. These results suggest that lanthanum neurotoxicity may lead to increased neuronal excitability. Moreover, given this inhibition of IK(A), lanthanum should not be used to block calcium current in studies of K+ currents.