ADHD-like behaviour in the offspring of female rats exposed to low chlorpyrifos doses before pregnancy

The aim of this study was to investigate how chronic low-dose chlorpyrifos exposure of female Wistar rats before and during pregnancy affects behavioural parameters in their offspring. Four months before pregnancy, we exposed three groups of rats to chlorpyrifos doses of 5, 10, and 15 mg kg(-1) body weight every day for 30 days, whereas one group received a single 30 mg kg-1 dose on gestational day 6. When the offspring of the exposed rats grew up, we studied their anxiety rate, motor activity, and cognitive abilities using the respective behavioural tests: open field test, dark/light box, and the extrapolation escape test. The offspring of rats exposed before pregnancy had significantly higher activity rate than controls, and even showed motor agitation and hyperactivity signs. The offspring of rats exposed to the single dose had difficulties solving the extrapolation escape test and showed poorer short-and long-term memory performance. This confirmed that even pre-pregnancy chlorpyrifos exposure can cause neurobehavioral consequences in offspring. Even though the mechanisms of the observed changes remain unclear and need further investigation, these data seem alarming and may serve as an important argument for revising the terms of safe pesticide use.