The insecticide esfenvalerate modulates neuronal excitability in mammalian central nervous system in vitro

Characterization in Potent Modulation on Voltage-Gated Na+ Current Exerted by Deltamethrin, a Pyrethroid Insecticide

Deltamethrin (DLT) is a type-II pyrethroid ester insecticide used in agricultural and domestic applications as well as in public health. However, transmembrane ionic channels perturbed by this compound remain largely unclear, although the agent is thought to alter the gating characteristics of voltage-gated Na⁺ (Na_V) channel current. In this study, we reappraised whether and how it and other related compounds can make any further modifications on voltage-gated Na⁺ current (I_Na) in pituitary tumor (GH₃) cells. Cell exposure to DLT produced a differential and dose-dependent stimulation of peak (transient, I_Na(T)) or sustained (late, I_Na(L)) I_Na; consequently, the EC₅₀ value required for DLT-stimulated I_Na(T) or I_Na(L) was determined to be 11.2 or 2.5 μM, respectively. However, neither the fast nor slow component in the inactivation time constant of I_Na(T) activated by short depolarizing pulse was changed with the DLT presence; conversely, tefluthrin (Tef), a type-I pyrethroid insecticide, can accentuate I_Na with a slowing in inactivation time course of the current. The I_Na(L) augmented by DLT was attenuated by further application of either dapagliflozin (Dapa) or amiloride, but not by chlorotoxin. During pulse train (PT) stimulation, with the Tef or DLT presence, the cumulative inhibition of I_Na(T) became slowed; moreover, following PT stimuli, a large tail current with a slowly recovering process was observed. Alternatively, during rapid depolarizing pulse, the amplitude of I_Na(L) and tail I_Na (I_Na(Tail)) for each depolarizing pulse became progressively increased by adding DLT, not by Tef. The recovery time constant following PT stimulation with continued presence of Tef or DLT was shortened by further addition of Dapa. The voltage-dependent hysteresis (Hys_(V)) of persistent I_Na was differentially augmented by Tef or DLT. Taken together, the magnitude, gating, frequency dependence, as well as Hys_(V) behavior of I_Na exerted by the presence of DLT or Tef might exert a synergistic impact on varying functional activities of excitable cells in culture or in vivo.

Agrochemicals and neurogenesis

Agrochemicals or pesticides are compounds widely used to prevent, destroy or mitigate pests such as insects, rodents, herbs and weeds. However, most of them also act as environmental estrogens, anti-estrogens and/or antiandrogenic chemicals. In addition, both herbicides (such as glyphosate and paraquat) and insecticides (such as pyrethroids, organophosphates, neonicotinoids and rotenone) have been shown to exert significant adverse effects on hippocampal neurogenesis. These effects are particularly important because neurogenesis dysregulation could be associated with cognitive decline and neuropathologies such as Alzheimer's disease. This review focuses on the most commonly used agrochemicals in Argentina and their effects on the hippocampal neurogenesis of mammals. It also discusses the disruption of hormone synthesis and action as a possible mechanism through which these chemical compounds could alter the brain functions. Finally, we propose some lines of research to study the potential endocrine mechanisms involved in the effects of agrochemicals on human health and biodiversity.

Effects of multiple environmental factors on elimination of fenvalerate and its cis-trans isomers in aquaculture water

Fenvalerate (FV) is widely used in aquaculture because of their broad spectrums and high efficiency. However, little is known regarding the elimination of FV influenced by environment factors in aquaculture water, especially its cis-trans isomers (cis-FV and trans-FV). In the present study, factors influencing the aquaculture environment (open type, temperature, pH and light) were selected, and the elimination dynamics of FV and its cis-trans isomers in aquaculture water using orthogonal experiments were investigated. The results showed that the half-life and elimination rate range of FV were 4.75-11.95 days and 65-93%, respectively, while those of trans-FV were 4.60-11.82 days and 67-93% and those of cis-FV were 4.94-12.04 days and 64-92%, respectively. The elimination rate of trans-FV was better than that of cis-FV. Additionally, analysis of variance (ANOVA) of the orthogonal experimental data indicated that the environmental factors of open type, temperature, and pH significantly influenced the elimination rate of cis- and trans-FV (P < 0.05), that is, in the aquaculture season, high temperature and pH facilitate to eliminate FV. This study would improve our understanding of natural degradation associated with FV and guide safe to use associated with pesticide in aquaculture.