Repeated exposures to chlorpyrifos lead to spatial memory retrieval impairment and motor activity alteration.

Chlorpyrifos (CPF) is one of the most commonly used insecticides throughout the world and has become one of the major pesticides detected in farm products. Chronic exposures to CPF, especially at the dosages without eliciting any systemic toxicity, require greater attention. The purpose of this study was, therefore, to evaluate the behavioral effects of repeated low doses (doses that do not produce overt signs of cholinergic toxicity) of CPF in adult rats. Male rats were given 0, 1.0, 5.0 or 10.0mg/kg of CPF through intragastric administration daily for 4 consecutive weeks. The behavioral functions were assessed in a series of behavioral tests, including water maze task, open-field test, grip strength and rotarod test. Furthermore, the present study was designed to evaluate the effects of repeated exposures to CPF on water maze recall and not acquisition. The results showed that the selected doses only had mild inhibition effects on cholinesterase activity, and have no effects on weight gain and daily food consumption. Performances in the spatial retention task (Morris water maze) were impaired after the 4-week exposure to CPF, but the performances of grip strength and rotarod test were not affected. Motor activities in the open field were changed, especially the time spent in the central zone increased. The results indicated that repeated exposures to low doses of CPF may lead to spatial recall impairments, behavioral abnormalities. However, the underlying mechanism needs further investigations.