Animal models in the neurotoxicology of 2,4-D.

2,4-D is a selective pre- and postemergence herbicide used for several crops. It is hazardous for the environment and risk for humans; therefore, several studies attempt to evaluate its effects and consequences of its use. The nervous system is supposedly a target for this herbicide, and this comprehensive review gathers the information about animal models that have been used for the study of the neurotoxicity of 2,4-D. The studies used several methods to evaluate the neurotoxicity of this herbicide, most of which used rodents, mainly rats, two used fish, and one used chicken eggs. The main behavioral effect observed concerned alterations in locomotor patterns and reduced motor activity. Biochemical analysis showed decreased levels of serotonin (5-HT) and increased levels of its metabolites and increased or decreased levels of DA and its metabolites depending on the brain area analyzed. Hypomyelination is also a possible effect of 2,4-D when the exposure occurs during the proliferation and development of the oligodendrocytes. The worst neuropathologic effects were observed in fish. Since most studies focused on the neurotoxicity of 2,4-D in rodents, the effect it may have on other species and groups of animals, especially with different physiology, is unclear and it should be researched.