A multi-approaches examination of toxicological effects of a naturally-occurring plant alkaloid veratridine, and the synthetic type II pyrethroid lambda-cyhalothrin on honey bees.

Synthetic insecticides used in agriculture are one of the major causes for the loss of biodiversity. Naturally-occurring substances have been envisioned by agrochemical companies as environmentally-friendly alternatives. Here, the effects of the plant alkaloid veratridine and a synthetic pyrethroid insecticide, lambda-cyhalothrin, were compared on honey bees, using electrophysiology, ethology, and classical toxicology. Both compounds triggered strong deleterious effects, in vitro and in vivo. In cell-cultured antennal lobe neurons, their effects were qualitatively similar with the appearance of a persistent tail current through voltage-gated sodium channels. Veratridine-induced tail current had much slower kinetics. Both compounds caused mortality in a similar range of doses. At sublethal exposure levels, only lambda-cyhalothrin caused strong behavioural defects. This work could pave the way to updating the current safety assessment framework for insecticides, showing that in vitro assays can help in anticipating lethal and sublethal toxicity of both natural and synthetic compounds.