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Published on: December 14, 2014
Effects of repeated oral postnatal exposure to chlorpyrifos on open-field behavior in juvenile rats
R L Carr1, H W Chambers, J A Guarisco
1Center for Environmental Health Sciences, Box 9825, College of Veterinary Medicine, Mississippi State University, Mississippi 39762, USA. rlcarr@cvm.msstate.edu
Insights
Early exposure to chlorpyrifos insecticide in young rats significantly reduced locomotor activity by juvenile ages. These behavioral changes occurred even after brain cholinesterase activity had largely recovered from the organophosphate exposure.
Area of Science:
- Neuroscience
- Toxicology
- Developmental Biology
Background:
- Organophosphorus (OP) insecticides, like chlorpyrifos, are known to potentially cause behavioral effects in children.
- Early life exposure to neurotoxicants is a significant concern for child development and long-term health outcomes.
Purpose of the Study:
- To investigate the effects of repeated early postnatal exposure to chlorpyrifos on the behavior of preweanling rats.
- To determine if chlorpyrifos exposure induces behavioral changes at both pre- and postweanling ages.
Main Methods:
- Preweanling rats were administered varying dosages of chlorpyrifos every other day from postnatal day (PND) 1 to PND 21.
- Locomotor activity was assessed using an open field test on multiple days between PND 10 and PND 30.
- Brain and peripheral cholinesterase (ChE) activity was measured to assess neurotoxic effects.
Main Results:
- High-dose chlorpyrifos exposure led to significantly reduced body weight in rats.
- Locomotor activity was significantly decreased in medium- and high-dosage groups on PND 25 and 30.
- Significant cholinesterase inhibition was observed in the brain, lung, diaphragm, and heart, with recovery noted by PND 30.
Conclusions:
- Early postnatal exposure to chlorpyrifos can depress locomotor activity in juvenile rats.
- The observed behavioral deficits were most pronounced after brain cholinesterase activity had substantially recovered.
- These findings highlight potential neurodevelopmental risks associated with early-life organophosphate insecticide exposure.
Abstract:
Organophosphorus (OP) insecticides have the potential to cause behavioral effects in children. This study was designed to determine if repeated oral exposure of preweanling rats to chlorpyrifos would produce behavioral changes at both pre- and postweanling ages. Treatment occurred every second day beginning on post-natal day (PND) 1, and continued through PND 21. The rats received one of the following regimens: a low-dosage (3 mg/kg) from PND 1-21; a medium dosage (mg/kg from PND 1-5, and then 6 mg/kg from PND 7-21; or a high-dosage schedule of 3 mg/kg on PND 1-5, then 6 mg/kg from PND 7-13, and 12 mg/kg from PND 15-21. There were no differences in body weights among the control-, low-, and medium-dosage groups but the high-dosage group had significantly lower body weights on PND 13-21. An open field was used to measure locomotor activity on PND 10, 12, 14, 16, 18, 20, 25, and 30. There were no differences in locomotor activity levels or treatment effects between males and females. On PND 10, 12, 14, 16, 18, and 20 there was no effect on locomotor activity with any dosage. On days 25 and 30, locomotor activity was significantly decreased with the medium- and high-dosage groups. Brain cholinesterase (ChE) inhibition was about 25-38% on PND 25 and 14-34% on PND 30. On PND 25 but not 30, lung and diaphragm ChE and serum butyrylcholinesterase (BChE), with the high-dosage animals, and heart ChE with the medium- and high-dosage groups were significantly inhibited. There was no significant inhibition of skeletal muscle ChE or serum acetylcholinesterase (AChE) on PND 25 and 30. These data suggest that early postnatal chlorpyrifos exposures will depress locomotor activity in juvenile rats, with the effects most pronounced after brain ChE activity has substantially recovered.
