The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is widely used in several countries. Research on the neurotoxicity of 2,4-D has been focused on the central nervous system, and little is known about its effects on the myenteric plexus. Therefore, to elucidate the neurotoxicity of 2,4-D and the viability of its use, we investigated the effects of daily intake of 5 mg 2,4-D/kg for 60 days on the myenteric plexus neurons of the rat ileum using quantitative and morphometric analyses. Twenty male Wistar rats aged 60 days were divided into two groups (n=10 rats/group). The group E animals received daily 5 mg doses of 2,4-D/kg diluted in 1 mL of water, whereas the group C animals were not treated with the herbicide. The animals were euthanized with anesthetic after 60 days; subsequently, the ileum was dissected out, and procedures were performed to visualize the total population of neurons (Giemsa staining), the nitrergic neurons (NADPHd+), and the estimated population of cholinergic neurons (NADPHd-). The results were statistically analyzed and compared between groups. In group E, the densities of Giemsa-stained neurons and NADPHd- neurons decreased (p<0.05) by 7% and 10%, respectively, whereas the density of NADPHd+ neurons remained constant. The cell body area was 5.8% greater (p<0.05) for the NADPHd+ neurons but remained unchanged for the neurons stained with Giemsa. These results suggest that 2,4-D causes a reduction in neuronal density, particularly for cholinergic neurons, and promotes an increase in the cell body area of nitrergic neurons, leading to hypertrophy.
Neurons of the Myenteric Plexus of the Rat Ileum Are Vulnerable to the Action of the Herbicide 2,4-Dichlorophenoxyacetic Acid
