Abstract
Air pollution is fully acknowledged to represent a major public health issue. Toxic environmental substances, such as ozone, interfere with prenatal development. Animals exposed to ozone (O3) in utero develop biochemical and morphological alterations. This gas has been proven to decrease cognitive capacity in different species. In the present study, we assessed the possible alterations in memory and spatial learning in the offspring of female rats who were exposed to 1.0 ppm of O3 embryonic development. Two instruments were used to evaluate possible alterations: the T-maze and a Skinner box. MAPK, ERK, p-ERK, and NR2B proteins, which are widely regarded as responsible for the learning process in the hippocampus and cortex, were also assessed by immunohistochemistry. We found that male rats exposed to O3 in utero displayed a significant delay to reach the correct response using the spatial learning test as compared to the control group. The female rats exposed to O3 showed a significant delay to reach the correct response as compared to the female control group in the Skinner box. We also found that while the male rats showed decrease in significant differences in the expression of NR2B, ERK and increase in MAPK. Females only showed increase in MAPK, p-ERK and decrease in ERK, when compared to their respective control group. It is possible that the deficits are associated to hormonal expression, inflammation and oxidative stress alterations. In summary, these results suggest that exposure to O3 can interfere with prenatal development, resulting in learning and memory deficiencies in rats.
Highlights
Air pollution is a major public health issue
After analyzing the average time each group took to obtain 75– 100% correct responses, we found no statistically significant differences when compared per day
Learning and memory processes are an example of nervous system plasticity associated to molecular change
Summary
Air pollution is a major public health issue. The global burden of disease attributed to environmental factors is estimated to be 25%, affecting 35% of children under 5 years of age (Prüss-Ustün et al, 2016). Ozone (O3) is one of the most common environmental pollutants. The dorsal hippocampus participates in learning processes and spatial memory, regions CA1, CA3 and the dentate gyrus (Gilbert and Brushfield, 2009). These regions have been found to differ in male and female rats during postnatal development, the difference has been attributed to the role of sex hormones (Roof, 1993; Woolley and McEwen, 1993). Adult rats exposed to 1.0 ppm of O3 for 4 h show a significant decrease in the number of dendritic spines of pyramidal neurons
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