title: Mechanisms of pyrethroid insecticide-induced stimulation of calcium influx in neocortical neurons.
abstract: Pyrethroid insecticides bind to voltage-gated sodium channels (VGSCs) and modify their gating kinetics, thereby disrupting neuronal function. Pyrethroids have also been reported to alter the function of other channel types, including activation of voltage-gated calcium channels. Therefore, the present study compared the ability of 11 structurally diverse pyrethroids to evoke Ca(2+) influx in primary cultures of mouse neocortical neurons. Nine pyrethroids (tefluthrin, deltamethrin, λ-cyhalothrin, β-cyfluthrin, esfenvalerate, S-bioallethrin, fenpropathrin, cypermethrin, and bifenthrin) produced concentration-dependent elevations in intracellular calcium concentration ([Ca(2+)](i)) in neocortical neurons. Permethrin and resmethrin were without effect on [Ca(2+)](i). These pyrethroids displayed a range of efficacies on Ca(2+) influx; however, the EC(50) values for active pyrethroids all were within one order of magnitude. Tetrodotoxin blocked increases in [Ca(2+)](i) caused by all nine active pyrethroids, indicating that the effects depended on VGSC activation. The pathways for deltamethrin- and tefluthrin-induced Ca(2+) influx include N-methyl-D-aspartic acid receptors, L-type Ca(2+) channels, and reverse mode of operation of the Na(+)/Ca(2+) exchanger inasmuch as antagonists of these sites blocked deltamethrin-induced Ca(2+) influx. These data demonstrate that pyrethroids stimulate Ca(2+) entry into neurons subsequent to their actions on VGSCs.
authors.affiliation: Department of Pharmacology, School of Medicine, Creighton University, Omaha, NE 68178, USA.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Cao
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Shafer
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Murray
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D007306:Insecticides / Q000494:pharmacology*; D051379:Mice; D019579:Neocortex / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D011722:Pyrethrins / Q000494:pharmacology*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D002118:Calcium