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Impacts of a perinatal exposure to manganese coupled with maternal stress in rats: Tests of untrained behaviors.

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Manganese (Mn), an element that naturally occurs in the environment, has been shown to produce neurotoxic effects on the developing young when levels exceed physiological requirements. To evaluate the effects of this chemical in combination with non-chemical factors pregnant Long-Evans rats were treated with 0, 2, or 4 mg/mL Mn in their drinking water from gestational day (GD) 7 to postnatal day (PND) 22. Half of the dams received a variable stress protocol from GD13 to PND9, that included restraint, small cage with reduced bedding, exposure to predator odor, intermittent intervals of white noise, lights on for 24 h, intermittent intervals of lights on during dark cycle and cages with grid floors and reduced bedding. One male and one female offspring from each litter were tested to assess untrained behavior. Ultrasonic vocalizations (USV) were recorded from PND13 pups while they were isolated from the litter. Locomotor activity (MA) was measured in figure-eight mazes at PND 17, 29, and 79 (different set of rats at each time point). Social approach (SA) was tested at PND48. Acoustic startle response (ASR) and pre-pulse inhibition (PPI) were measured starting at PND58. At PND53 a sweetness preference for a chocolate flavored milk solution was assessed. There were sex related differences on several parameters for the USVs. There was also a Mn by stress by sex interaction with the females from the 4 mg/mL stressed dams having more frequency modulated (FM) call elements than the 4 mg/mL non-stressed group. There was an effect of Mn on motor activity but only at PND29 with the 2 mg/mL group having higher counts than the 0 mg/mL group. The social approach test showed sex differences for both the habituation and test phase. There was an effect of Mn, with the 4 mg/mL males having a greater preference for the stimulus rat than did the 0 mg/mL males. There was also a stress by sex interaction. The ASR and PPI had only a sex effect. Thus, with only the FM call elements having a Mn by stress effect, and the PND29 MA and SA preference index having a Mn effect but at different doses requires further investigation.

Impact/Purpose

Manganese, an essential element has been shown to have neurotoxic effects on the developing young.  Stress during pregnancy has also shown to effect the developing young in humans and animals.  All of these stressors (including certain chemicals) are disproportionately found in lower socioeconomic groups and has become an increased concern for the EPA Environmental Justice program.  This concern led to research under the Sustainable and Healthy Communities (SHC) program.  In order to quantify neurobehavioral adverse outcomes in rats exposed to Manganese (Mn) in combination with psychosocial and physiological stressors in utero(prenatal) and also during postnatal development we exposed pregnant rats to 0, 2, or 4 mg/mL of Mn in their drinking water.  Half of the animals in each dose group received a variable stress protocol.  The offspring were assessed in several tests of untrained behaviors.  The data from this research may be used in risk assessment to assess the risks to disproportionally impacted communities, and also used to make decisions on community interventions that may improve health and well - being.

Citation

McDaniel, K., T. Beasley, W. Oshiro, M. Huffstickler, V. Moser, AND D. Herr. Impacts of a perinatal exposure to manganese coupled with maternal stress in rats: Tests of untrained behaviors. Elsevier Science Ltd, New York, NY, 91(107088):1, (2022). [DOI: 10.1016/j.ntt.2022.107088]

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DOI: Impacts of a perinatal exposure to manganese coupled with maternal stress in rats: Tests of untrained behaviors.
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Last updated on April 12, 2022
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