Perinatal exposure to an environmentally relevant mixture of phthalates results in a lower number of neurons and synapses in the medial prefrontal cortex and decreased cognitive flexibility in adult male and female rats

• Published in: The Journal of neuroscience Vol. 38; no. 31; pp. 6864 - 6872
• Main Authors: Kougias, Daniel G, Sellinger, Elli P, Willing, Jari, Juraska, Janice M
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 01.08.2018
• Subjects: Adults; Brain; Brain architecture; Cognitive ability; Consumer products; Endocrine disruptors; Exposure; Flexibility; Genetic crosses; Hormones; Lactation; Long-term effects; Mental disorders; Neuronal-glial interactions; Neurons; Offspring; Perinatal exposure; Phthalate esters; Phthalates; Placenta; Prefrontal cortex; Pregnancy; Rats; Rodents; Synapses
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/JNEUROSCI.0607-18.2018

The growth and organization of the developing brain is known to be influenced by hormones, but little is known about whether disruption of hormones affects cortical regions, like the medial prefrontal cortex (mPFC). This region is particularly important given its involvement in executive functions and implication in the pathology of many neuropsychiatric disorders. Here, we examine the long-term effects of perinatal exposure to endocrine-disrupting compounds, the phthalates, on the mPFC and associated behavior. This investigation is pertinent as humans are ubiquitously exposed to phthalates through a variety of consumer products and phthalates can readily cross the placenta and be delivered to offspring via lactation. Pregnant dams orally consumed an environmentally relevant mixture of phthalates at 0, 200, or 1000 μg/kg/day through pregnancy and for 10 days while lactating. As adults, offspring were tested in an attentional set-shifting task, which assesses cognitive flexibility. Brains were also examined in adulthood for stereological quantification of the number of neurons, glia, and synapses within the mPFC. We found that, independent of sex, perinatal phthalate exposure at either dose resulted in a reduction in neuron number, synapse number, and size of the mPFC and a deficit in cognitive flexibility. Interestingly, the number of synapses was correlated with cognitive flexibility, such that rats with fewer synapses were less cognitively flexible than those with more synapses. These results demonstrate that perinatal phthalate exposure can have long-term effects on the cortex and behavior of both male and female rats. Humans globally are exposed on a daily basis to a variety of phthalates, which are endocrine-disrupting chemicals. The effects of phthalate exposure on the developing brain, especially on cognitively relevant regions like the medial prefrontal cortex (mPFC), is not known. Here, we use a rat model of human prenatal exposure to an environmentally relevant mixture of phthalates and find there is an appreciable reduction in neuron number, synapse number, and size of the mPFC and a deficit in cognitive flexibility. These results may have serious implications for humans given the mPFC is involved in executive functions and is implicated in the pathology of many neuropsychiatric disorders.