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Honey Bees: Estimating the Environmental Impact of Chemicals - Chapter 6

Hệ thống cholinergic ở côn trùng là mục tiêu chính của thuốc trừ sâu. Một lớp học của các phân tử, các neonicotinoids, trực tiếp cảm ứng kích hoạt các thụ thể nicotinic acetylcholine thần kinh các (nAChRs). Trong các thụ thể của ong mật là luận án phân phối chủ yếu trong các đường liên kết tế bào thần kinh khứu giác cảm giác tới thùy antennal và bodysuits nấm. Cấu trúc luận án dường như vai trò quan trọng năm trong điều khứu giác | 6 Effects of imidacloprid on the neural processes of memory in honey bees C. Armengaud M. Lambin and M. Gauthier Summary The cholinergic system in insects is the main target of insecticides. One class of molecules the neonicotinoids induces direct activation of the neuronal nicotinic acetylcholine receptors nAChRs . In the honey bee these receptors are mainly distributed in the olfactory pathways that link sensory neurons to antennal lobes and mushroom bodies. These structures seem to play an important role in olfactory conditioning. We have previously shown that cholinergic antagonists injected in different parts of the brain impaired the formation and retrieval of olfactory memory. We then advanced the hypothesis that through the activation of the nAChR the neonicotinoid imidacloprid IMI would lead to facilitation of the memory trace. To test this hypothesis IMI was applied topically upon the thorax and the effects were tested on the habituation of the proboscis extension reflex induced by repeated sugar stimulation of the antennae. Animals treated with IMI to a dose that did not affect sensory or motor functions needed fewer trials than nontreated animals to show a reflex inhibition. This effect can be interpreted as a learning facilitation. We developed a functional histochemistry of cytochrome oxidase CO to reveal the brain targets of the drug in the honey bee brain. Following IMI injection a CO staining increase probably linked to an increase in metabolism was observed in the antennal lobes. In integrative structures in particular the calyces of mushroom bodies IMI exerted a facilitatory or inhibitory effect on neuronal metabolism depending on the dose. The brain targets of nicotinic ligands including pesticides can be compared by using this technique. Introduction Two of the three main classes of insecticides exert their neurotoxic effects through action on the cholinergic system. This is the case for the new class of neonicotinoids which are known to act on