Insecticides are pesticides used to control insects in agriculture, ornamental gardens, homes, and veterinary medicine. Although the toxic effects on the environment and the health of living beings are not fully understood, these pesticides have become the first options for crop protection in agriculture. After herbicides, insecticides are the most extensively used pesticides in agriculture, with large quantities consumed on every continent, primarily in America. Chlorpyrifos, carbaryl, and imidacloprid are among the top ten most used insecticides. Amidst organophosphates, chlorpyrifos has been reported to be used in over fifty food crops. Carbaryl is a carbamate employed as an insecticide, fungicide, herbicide, and nematicide. Similarly, neonicotinoids are the most used insecticide on a global scale. Neonicotinoids include imidacloprid, the second most frequently used pesticide, surpassed only by glyphosate. It is used because it is less toxic to humans. However, insects appear to be less resistant to its compounds. Evidence suggests that these insecticides persist in soils for a long time and have neurotoxic effects in animal species not intended to receive its consequences. Thus, this chapter’s aim is to describe these three pesticides effects and contrast them with the most recent findings regarding their neurotoxic effects in various animal species.
Neonicotinoids are pesticides that act as agonists of nicotinic receptors for acetylcholine in insects’ central nervous system (CNS). Chronic exposure to neonicotinoids in humans is related to autism, memory loss, and finger tremor. In this article, we evaluate the effect of subchronic oral administration of two neonicotinoids in the same mixture: clothianidin and thiacloprid. Decreasing doses of both pesticides were administered to rats starting from the lethal dose 50 (LD50) reported by the manufacturer. Our results indicate that the administration of three doses of decreasing amounts of LD50 (5/10, 4/10, and 3/10 LD50) resulted in 100% death in all cases. Ten administration times of 2/10 LD50 of the mixture caused only 20% of death cases after twenty-seven days, which was determined as a subchronic administration scheme. The animals administered 2/10 LD50 showed behavioral alterations after the first and second administration. Electrographic studies showed abnormal discharge patterns in the CNS. 72 h after the tenth dose, learning and memory tests were performed in the Morris water maze. Our results revealed significant decreases in permanence at the quadrant and the number of crosses ( P = 0.0447 , P = 0.0193 , respectively), which represent alterations in the short-term memory test, but there were no significant changes in a long-term memory test. Likewise, the brains of these animals showed tissue architecture loss, nucleosomal retraction, and a significant increase in the pycnosis of the granular neurons of the dentate gyrus analyzed at 72 h after the last dose ( P = 0.0125 ). Toxic effects and cognitive deterioration that have been found in communities living near contaminated areas are probably related to the agricultural use of neonicotinoids.
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