Effect of alpha-cypermethrin and theta-cypermethrin on delayed rectifier potassium currents in rat hippocampal neurons

Cypermethrin is a photostable synthetic pyrethroid and the most widely used Type 11 pyrethroid pesticide. The effects of two different stereoisomers of cypermethrin insecticides, alpha-cypermethrin and theta-cypermethrin, on the delayed rectifier potassium current (I-K) in hippocampal neurons of rat, were studied using whole-cell patch clamp technique. Alpha-cypermethrin and theta-cypermethrin decreased the amplitude value of I-K, and shifted the steady state activation curve of I-K towards negative potential at any concentrations (10(-9) M, 10(-8) M, 10(-7) M). Furthermore, at higher concentration, alphacypermethrin (10(-7) M) and theta-cypermethrin (10(-8) M, 10(-7) M) had observable effects (if the steady state inactivation Of I-K. The results suggest that I-K is the target of alpha-cypermethrin and theta-cypermethrin, which may explain the mechanism of toxic effects of both steroeisomers of cypermethrin on mammalian neurons. Cypermethrin-altered properties of voltage gated delayed rectifier K* channels may contribute to neurotoxicity by eliciting abnormal electrical discharges in hippocampal CA3 neurons. (C) 2009 Elsevier Inc. All rights reserved.