Imidacloprid (CHEM000710)

Imidacloprid is a neonicotinoid insecticide, which is a class of neuro-active insecticides modeled after nicotine. Nicotine was identified and used as an insecticide and rat poison as early as the 1600’s. Its effectiveness as an insecticide spurred a search for insecticidal compounds that have selectively less effect on mammals, which led to the discovery of neonicotinoids. Neonicotinoids, like nicotine, bind to nicotinic acetylcholine receptors of a cell. In mammals, nicotinic acetylcholine receptors are located in cells of both the central and peripheral nervous systems. In insects these receptors are limited to the CNS. While low to moderate activation of these receptors causes nervous stimulation, high levels overstimulate and block the receptors causing paralysis and death. Nicotinic acetylcholine receptors are activated by the neurotransmitter acetylcholine. Acetylcholine is broken down by acetylcholinesterase to terminate signals from these receptors. However, acetylcholinesterase cannot break down neonicotinoids and the binding is irreversible. Because most neonicotinoids bind much more strongly to insect neuron receptors than to mammal neuron receptors, these insecticides are selectively more toxic to insects than mammals. The low mammalian toxicity of neonicotinoids can be explained in large part by their lack of a charged nitrogen atom at physiological pH. The uncharged molecule can penetrate the insect blood–brain barrier, while the mammalian blood–brain barrier filters it. However, Some neonicotinoid breakdown products are toxic to humans, especially if they have become charged. Because of their low toxicity and other favorable features, neonicotinoids are among the most widely used insecticides in the world. Most neonicotinoids are water-soluble and break down slowly in the environment, so they can be taken up by the plant and provide protection from insects as the plant grows. Neonicotinoids are currently used on corn, canola, cotton, sorghum, sugar beets and soybeans. They are also used on the vast majority of fruit and vegetable crops, including apples, cherries, peaches, oranges, berries, leafy greens, tomatoes, and potatoes. The use of neonicotinoids has been linked in a range of studies to adverse ecological effects, including honey-bee colony collapse disorder (CCD) and loss of birds due to a reduction in insect populations. This has led to moratoriums and bans on their use in Europe.