Calcium channels, effects pyrethroids

Other target sites for certain pyrethroids include the voltage-gated calcium and chloride channels. Of particular interest is the increased effect of Type II pyrethroids on certain phosphoforms of the N-type Cav2.2 calcium channel following post-translational modification and its relationship to enhanced neurotransmitter release seen in vivo. 

Neurotransmitter release induced by potassium-dependent depolarization is a physiologically relevant way to investigate pyrethroid effects on calcium-dependent neurotransmitter release since this process is independent of voltage-sensitive sodium channels [71]. Furthermore, potassium-stimulated calcium influx and subsequent neurotransmitter release by synaptosomes is blocked by a variety of voltage-sensitive calcium channel antagonists but not by TTX [4, 71, 72]. 

Shafer TJ, Meyer DA (2004) Effects of pyrethroids on voltage-sensitive calcium channels a critical evaluation of strengths, weaknesses, data needs, and relationship to assessment of cumulative neurotoxicity. Toxicol Appl Pharmacol 196 303-318... 

In view of the very critical role calcium channels play in a variety of nerve and muscle function, possible effects of various insecticides on calcium channels are too important to be overlooked. It was indeed shown that neurosecretory cells of the stick insect generate action potentials by inward calcium currents (48), and that permethrin increases the electrical activity of these cells at a concentration as low as 5 x 10 " M (49). Although direct demonstration still remains to be seen, it is possible that pyrethroids act on calcium channels to exert their toxic effects (48.50). 

F. Matsumura, sponsored by the National Institute of Environmental Health Sciences (NIEHS), plans to study the toxic effects of chlorinated and pyrethroid pesticides primarily on calcium and sodium regulating processes in the nervous system. To examine the interactions of the pesticides with calcium regulating processes, researchers will use synaptosomal preparations from the brains of rats and the central nervous systems of squid. To examine the interactions of the pesticides with sodium regulating processes, they will collect antibodies directed against sodium channel proteins. 

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