Bioaccumulation and neurotoxicity of dithiopyridine herbicide in the brain of freshwater fish,Cyprinus carpio

Abstract

The freshwater carp, Cyprinus carpio, was exposed to 0.5 mg (30% of median lethal concentration (LC₅₀)), 1.0 mg (60% of LC₅₀), and 1.6 mg (LC₅₀) of dithiopyridine herbicide per liter for acute (24 h) and 1/10 of LC₅₀ (0.2 mg/L/day) for sublethal (1, 3, 7, 14, and 21 days) experiments. The herbicide bioaccumulation was significantly affected by the acute exposure levels and the experimental periods and was positively correlated with them. One-way analysis of variance revealed that the acute and sublethal exposure to the herbicide as well as the experimental periods caused significant reduction in the concentrations of catecholamines (dopamine (DA) and norepinephrine (NE)), elevation of acetylcholine (ACh), and was associated with a marked decrease in the activity of acetylcholinesterase (AChE). In comparison with the corresponding controls, most levels of the DA and NE and the activity of AChE were significantly decreased, whereas the concentration of ACh was markedly elevated, during acute and sublethal exposure. In the acute and sublethal experiments, the herbicide accumulated in the brain was inversely proportional to the levels of DA and NE and the activity of AChE but has a direct correlation with the concentration of ACh. In addition, the brain’s AChE activity was negatively correlated with ACh content during the acute (r = −0.94) and sublethal (r = −0.78) experiments.