Abstract
The aims of our present study were to establish a novel olfactory-based spatial learning test and to examine the effects of exposure to nano-sized diesel exhaust-origin secondary organic aerosol (SOA), a model environmental pollutant, on the learning performance in preweaning mice. Pregnant BALB/c mice were exposed to clean air, diesel exhaust (DE), or DE-origin SOA (DE-SOA) from gestational day 14 to postnatal day (PND) 10 in exposure chambers. On PND 11, the preweaning mice were examined by the olfactory-based spatial learning test. After completion of the spatial learning test, the hippocampus from each mouse was removed and examined for the expressions of neurological and immunological markers using real-time RT-PCR. In the test phase of the study, the mice exposed to DE or DE-SOA took a longer time to reach the target as compared to the control mice. The expression levels of neurological markers such as the N-methyl-d-aspartate (NMDA) receptor subunits NR1 and NR2B, and of immunological markers such as TNF-α, COX2, and Iba1 were significantly increased in the hippocampi of the DE-SOA-exposed preweaning mice as compared to the control mice. Our results indicate that DE-SOA exposure in utero and in the neonatal period may affect the olfactory-based spatial learning behavior in preweaning mice by modulating the expressions of memory function–related pathway genes and inflammatory markers in the hippocampus.
Highlights
Exposure to environmental pollutants containing nano-sized particles during the developmental period might represent a major risk factor for children or the health of the generation
We measured the time required for the mice to reach the target and found that the mice exposed to diesel exhaust (DE), DE-secondary organic aerosol (SOA), or gas took a longer time to reach the target as compared to the control mice (Figure 2)
We found that preweaning mice exposed to DE, DE-origin SOA (DE-SOA), or gas during the brain development period showed an increased time to reach the target as compared to the control mice
Summary
Exposure to environmental pollutants containing nano-sized particles during the developmental period might represent a major risk factor for children or the health of the generation. Diagnosis is necessary for proper treatment to prevent disability in the later life of children. A variety of species have the ability to learn from the surrounding cues and use such spatial memory to navigate, using landmarks from any position to a specific location. Many tests are well-established to examine learning and memory functions in adults, there are very limited tests to examine learning and memory functions in neonates. There is only one report in the literature indicating that olfactory-based spatial learning in neonatal mice is associated with Ca2+/calmodulin-dependent protein kinase (CaMKII). In the hippocampal neurons [1]. With this background, we were prompted to establish a novel neonatal mouse model for early examination of learning using olfactory-based learning performance
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